CONGRESS OF THE UNITED STATES

CONGRESSIONAL BUDGET OFFICE

CBO

The U.S. Military’s 

Force Structure: 

A Primer

JULY 2016
CBO

Notes

Unless otherwise indicated, all years referred to in this study are federal fiscal years (which run 

from October 1 to September 30 and are designated by the calendar year in which they end). 

In addition, all costs apply to fiscal years and are expressed in fiscal year 2017 dollars of total 

obligational authority, and all growth rates are measured in real terms (with the adjustments 

for inflation made using the Congressional Budget Office’s projection of the gross domestic 

product price index).

Numbers in the text and tables may not sum to totals because of rounding.

Supplemental information for this analysis is available on CBO’s website (www.cbo.gov/

publication/51535).

www.cbo.gov/publication/51535
Contents

CBO

Summary 1

What Are the Major Elements of the Military’s Force Structure? 1

What Does This Analysis Indicate About the Budgetary Effects of 

Altering the Force Structure? 4

How Is This Report Organized? 5

1 Introduction 7

What Is Force Structure? 8

BOX 1-1. DEFINING SUPPORT UNITS 10

How CBO Estimated the Costs of the Military’s Force Structure 10

How Changes in the Force Structure Would Affect Costs 12

BOX 1-2. WHY CBO PROJECTS THAT MOST OF DOD’S OPERATION AND

SUPPORT COSTS ARE PROPORTIONAL TO THE FORCE STRUCTURE 14

Costs Not Included in This Analysis 15

Guide to Reading This Report 16

2 Department of the Army 17

Overview 17

BOX 2-1. COMMAND LEVELS OF U.S. GROUND FORCES 19

Major Elements of the Force Structure

Army Armored Brigade Combat Teams 22

Army Stryker Brigade Combat Teams 28

Army Infantry Brigade Combat Teams 32

Other Department of the Army Units and Activities 36

Special Topics

Integration of the Army’s Active and Reserve Components 38

Manning Levels, Readiness, and Deployability of Units 40

Deployment Times and Rotation Ratios 42
II THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

3 Department of the Navy 45

Overview 45

Major Elements of the Force Structure

Aircraft Carriers 52

Surface Combatants 56

Attack Submarines 59

Amphibious Ships 61

Marine Corps Infantry Battalions 65

Other Department of the Navy Units and Activities 68

Special Topics

Integration of the Navy and Marine Corps 70

Forcible-Entry Capability 72

Naval Shipborne Aviation 74

Marine Corps Aviation 77

4 Department of the Air Force 81

Overview 81

Major Elements of the Force Structure

Air Force Tactical Aviation Squadrons 86

Air Force Bomber Squadrons 89

Air Force Airlift Squadrons 92

Air Force Air Refueling Squadrons 96

Air Force Unmanned Air System Squadrons 100

Other Department of the Air Force Units and Activities 103

Special Topic

The U.S. Military’s Strike Capability 105

5 Defensewide Activities 109

Overview 109

Major Elements of the Force Structure

Special Operations 111

Defense Health Program 114

Other Defensewide Units and Activities 116

Nuclear Forces 117

Missile Defense 120
CONTENTS THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER III

CBO

A Size, Costs, and Number of U.S. Forces 123

B Reconciling CBO’s and DoD’s Five-Year Tallies of Funding and Personnel 127

C Military Operations and Planning Scenarios Referred to in This Report 135

List of Tables and Figures 139

About This Document 140

CBO

Summary

In fiscal year 2015, the Department of Defense (DoD) 

spent a total of roughly $390 billion on operation and 

support (O&S) of military units. The O&S budget covers the costs associated with the day-to-day running of 

units. Those costs include pay and benefits for military 

personnel, compensation for most civilian employees, 

health care costs for military and civilian personnel, and 

the daily expenses of operating a unit, such as equipment 

maintenance, training, support contractors, and so on. 

The O&S budget makes up about two-thirds of DoD’s 

total “base” budget, which is the defense budget excluding additional funds provided specifically for wartime 

operations. (The rest of DoD’s base budget is spent on 

acquiring weapon systems and constructing buildings 

and other infrastructure.) 

The size and complexity of the U.S. armed forces can 

make it difficult to determine how the O&S budget is 

distributed among units. In this report, the Congressional Budget Office analyzes the structure and cost of 

the military from the perspective of major combat units, 

such as Army brigades, Navy aircraft carrier strike groups, 

Marine Corps task forces, and Air Force squadrons. CBO 

allocates most of the O&S budget and DoD’s total number of military personnel among major combat units—

and their associated support units and overhead activities—to provide a clearer picture of the size and cost of 

the major elements of the military’s force structure. Such 

information can help policymakers evaluate proposals to 

change the structure or budget of the armed forces.

CBO’s analysis indicates that major combat units by 

themselves account for roughly one-quarter of DoD’s 

operation and support costs and contain about one-third 

of DoD’s military personnel. Most of the rest of DoD’s 

O&S costs and military personnel are associated either 

with units that support major combat units (which CBO 

considers part of the cost of maintaining fully supported 

major combat units) or with overhead activities necessary 

for manning, equipping, and training combat and support units. In addition, the total operating costs associated with a major combat unit include a share of the costs 

of “defensewide” activities, such as the Defense Health 

Program, that provide various forms of administrative 

support to DoD as a whole.

As an example, by CBO’s calculation, an armored brigade 

in the Army’s active component has about 4,200 military 

personnel assigned to it. But that number rises to about 

17,450 military personnel if it includes the units that 

support the armored brigade (by providing transportation and maintenance, for example) and the brigade’s 

proportional share of overhead activities that support 

DoD and the Army (such as recruiting, basic training, 

and administrative support). By itself, such an armored 

brigade costs $500 million a year to operate, including 

compensation for its military personnel. Those operating 

costs rise to about $2,600 million per year if the costs of 

support units and overhead activities are included (see 

Summary Table 1). Those patterns are similar for major 

combat units in the Department of the Navy (which 

includes the Marine Corps) and the Department of the 

Air Force.

What Are the Major Elements of the 

Military’s Force Structure?

Each of DoD’s three military departments provides different kinds of forces. The composition, functions, capabilities, and costs of the departments’ major combat units 

are often difficult to determine from budget documents 

and from the various reports that the military provides to 

the Congress. The critical roles that support units play in 

making major combat units function effectively are even 

more difficult to discern, as are the costs of supporting 

each type of combat unit. 

This primer describes how each department is organized 

into major combat units, what each type of unit does, 
2 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Summary Table 1.

Number, Size, and Costs of Selected U.S. Forces

Source: Congressional Budget Office, using data from the Department of Defense’s 2017 budget request.

“Direct” personnel and costs are associated with a major combat unit. “Total” personnel and costs also include the “indirect” personnel and costs 

associated with units that support the major combat unit and the “overhead” personnel and costs associated with the major combat unit’s share of 

administrative or overhead activities. For more information, see Chapter 1. The personnel and cost numbers shown here are rounded to the nearest 

10 personnel or $10 million; more detailed information is presented in Appendixes A and B.

a. Notional squadrons of 12 aircraft (actual squadrons vary in size).

how those units have been used in past conflicts, and how 

much it costs to operate and support those units. DoD 

also includes a number of smaller organizations that provide services or specialized capabilities to the military as a 

whole. In this analysis, CBO treats some of those defensewide costs as part of the cost of a military unit, which 

means that the total cost to operate and sustain all of a 

military department’s units is larger than the department’s requested O&S budget (because each department 

relies on services and activities funded from such 

defensewide accounts).

Department of the Army

According to its 2017 budget request, DoD plans to 

spend an average of about $101 billion per year (in 2017 

dollars) over the 2017–2021 period to operate and support 

Army units. The total O&S cost of those units includes 

an additional $16 billion per year from defensewide 

accounts, CBO estimates. 

Active-Component Armored Brigade 

Combat Team 9 4,200 17,450 500 2,610

Active-Component Stryker Brigade 

Combat Team 7 4,440 17,180 500 2,560

Active-Component Infantry Brigade 

Combat Team 14 4,230 16,250 450 2,410

Aircraft Carrier 11 3,200 6,590 470 1,180

Carrier Air Wing 10 1,630 4,860 330 910

Arleigh Burke Class Destroyer (DDG-51) 66 340 720 60 140

Attack Submarine 51 190 390 70 140

Amphibious Ship 33 710 1,450 110 270

Active-Component Marine Corps 

Infantry Battalion 24 1,490 5,780 140 740

F-16 Fighter Aircraft Squadrona 45 450 1,250 70 220

B-1B Bomber Aircraft Squadrona 4 940 3,980 270 810

C-17 Cargo Aircraft Squadrona 14 450 1,390 90 270

KC-135 Tanker Aircraft Squadrona 30 610 1,930 110 360

MQ-9 “Reaper” Unmanned Air 

System Squadrona 23 340 920 50 160

Department of the Army

Department of the Navy

Department of the Air Force

Number of

Direct Direct

Military Personnel per Unit

Annual Cost per Unit

(Millions of 2017 dollars)

Units in 2017 Total Total
SUMMARY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 3

CBO

Summary Figure 1.

Five-Year Average of Operation and Support 

Funding for Department of the Army Units

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

The main units that the Army provides to the U.S. military are brigade combat teams (BCTs), large formations 

that officially contain about 4,400 to 4,700 soldiers.1

Those units come in three major types: armored BCTs, 

Stryker BCTs, and infantry BCTs. All three types are 

similar in size; they differ primarily in how many wheeled 

or tracked vehicles are assigned to them. All BCTs are 

versatile ground combat units, capable of performing a 

wide variety of missions, and all rely on many support 

units assigned to them from higher-level commands. 

When deployed, a BCT can expect to be supported by 

almost twice as many personnel in support units as it has 

in its own unit. BCTs account for over 80 percent of 

O&S funding for Army units (see Summary Figure 1).

Department of the Navy

According to its 2017 budget request, DoD plans to 

spend an average of about $95 billion per year over the 

2017–2021 period to operate and support Navy and 

Marine Corps units. The total O&S cost of those units 

includes an additional $10 billion per year from 

defensewide accounts, CBO estimates. 

The Navy’s primary units are various kinds of battle force 

ships: aircraft carriers, surface combatants (cruisers, 

destroyers, and some smaller ships), attack submarines, 

and amphibious ships. Each type of ship is specialized for 

particular missions—such as carrying attack aircraft or a 

task force of marines—and the types differ greatly in size 

and cost. Battle force ships are relatively self-contained 

when deployed, although they receive support from some 

other units, including logistics ships that refuel and rearm 

them while they are under way, maritime patrol aircraft 

that scout for them, and minesweeper squadrons that 

clear their path of sea mines. Of Navy units (as opposed 

to Marine Corps units), aircraft carriers and their associated air wings account for the largest single share of O&S 

funding, receiving 21 percent of appropriations for the 

Department of the Navy’s units (see Summary Figure 2).

The Marine Corps’ main units are Marine air-ground 

task forces—integrated combinations of ground combat 

units, air combat units, and support units that are tailored to specific operations (rather than being standardized units, as in the other services). Different kinds of 

task forces are distinguished primarily by the size of 

their ground combat forces, from the small Marine expeditionary units carried on Navy amphibious ships up to 

the large Marine expeditionary forces that engaged in 

combat operations in Iraq in 1991 and 2003. Marine 

Corps units account for the largest single share—33 percent—of O&S funding for the Department of the Navy’s 

units (see Summary Figure 2).

Department of the Air Force

According to its 2017 budget request, DoD plans to 

spend an average of about $82 billion per year over the 

2017–2021 period to operate and support Air Force 

units. The total O&S cost of those units includes an 

additional $8 billion per year from defensewide accounts, 

CBO estimates. 

The majority of Air Force units consist of squadrons of 

different types of fixed-wing aircraft that perform a 

1. Those personnel numbers are based on the Army’s Table of 

Organization and Equipment, which serves as an official template 

for different types of Army units. In practice, units do not always 

conform to their templates for a variety of reasons. As a result, the 

personnel numbers for BCTs shown in Summary Table 1—which 

are based on DoD’s 2017 budget request—are smaller than the 

personnel numbers in the Army’s Table of Organization and 

Equipment. 

Armored Brigade

Combat Teams

(24%)

Stryker Brigade

Combat Teams

(17%)

Infantry Brigade

Combat Teams

(40%)

Other Units and

Activities

(19%)
4 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Summary Figure 2.

Five-Year Average of Operation and Support 

Funding for Department of the Navy Units

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

variety of missions: short-range tactical aircraft (for 

engaging in air-to-air combat with other aircraft or 

for striking targets on the ground), long-range bombers, 

airlifters (for transporting cargo and personnel), tankers 

(for refueling other aircraft in flight), and unmanned air 

systems (also known as drones). Short-range tactical aircraft account for the largest single share—33 percent—of 

O&S funding for the Department of the Air Force’s units 

(see Summary Figure 3).

Defensewide Activities

DoD also includes a number of defensewide organizations, 

which are not part of a military service, that perform specific functions. Most of those organizations—such as 

DoD’s military health care system—provide centralized 

forms of support that assist each of the services. But a 

few—such as Special Operations Command, which organizes units from the different services’ special-operations 

forces into an integrated force—provide distinct military 

capabilities to the nation (as well as generating distinct 

costs). Together, defensewide organizations and activities 

account for about $39 billion per year of the O&S funding 

that DoD requested in its 2017 budget. 

What Does This Analysis Indicate 

About the Budgetary Effects of 

Altering the Force Structure? 

This report breaks down DoD’s total number of military 

personnel and total operation and support budget and 

ascribes almost all personnel and O&S costs to major 

combat units according to three categories: 

B Direct personnel and O&S costs—for a major combat 

unit itself; 

B Indirect personnel and O&S costs—for the deployable units that support the major combat unit; and

B Overhead personnel and O&S costs—for the administrative functions within a service or DoD that are 

necessary to field the major combat unit and its 

supporting units.

CBO’s numbers are based on information in DoD’s latest 

five-year budget plan, the Future Years Defense Program 

for the 2017–2021 period. Thus, to the extent that DoD 

has overestimated or underestimated the funding needed

Summary Figure 3.

Five-Year Average of Operation and Support 

Funding for Department of the Air Force Units

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

Aircraft Carriers and

Carrier Air Wings

(21%)

Surface Combatants

(14%)

Marine Corps Units

(33%)

Other Units and

Activities

(16%)

Attack Submarines (7%)

Amphibious Ships (9%)

Tactical Aviation

Squadrons

(33%)

Bomber Squadrons

(10%)

Unmanned Air Systems (6%)

Other Units and

Activities

(21%)

Airlift Squadrons

(15%)

Air Refueling Squadrons

(14%)
SUMMARY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 5

CBO

to operate its forces, the estimates in this report will 

reflect that. The only O&S costs not divided among 

major combat units in this analysis are health care costs 

for current military retirees and their families, because 

those costs represent a major expense that DoD could not 

alter in the near term through future policy decisions.

If DoD or lawmakers decided to eliminate a major combat unit from DoD’s plans, the savings might not be as 

large as CBO’s estimate of the total O&S costs for that 

type of unit. DoD would achieve savings from the support units associated with a combat unit only if it also 

eliminated those units. And DoD would achieve savings 

in overhead functions only if it trimmed those activities 

to reflect the smaller force. In addition, some overhead 

activities, such as operating bases, might take several years 

to cut, which would delay the full savings. For related reasons, if policymakers decided instead to add a major combat unit to the military’s force structure, the costs might 

not be as large as CBO’s estimate of the O&S costs for 

that type of unit, at least in the near term.

However, the estimates of O&S costs for combat units 

presented in this report do not include the costs of developing and acquiring new weapon systems. Thus, if DoD 

or lawmakers chose to eliminate a major combat unit and 

stopped purchasing the weapon systems intended to 

equip that unit, the savings would be larger than CBO’s 

estimate of the costs to operate and sustain the unit. 

Similarly, if policymakers chose to add a major combat 

unit and to purchase weapon systems to equip that unit, 

the total additional costs would be larger than CBO’s 

estimate of the corresponding O&S costs.

How Is This Report Organized?

This primer is designed to be a reference work rather than 

a linear narrative. Chapter 1 describes CBO’s conceptual 

approach to analyzing the military’s force structure and 

costs, and the following three chapters discuss the particular organizational structures and roles of the Departments of the Army, the Navy, and the Air Force. All of a 

department’s major types of combat unit have their own 

entries, which discuss the size, cost, function, advantages, 

disadvantages, and past use of that type of unit. The final 

chapter includes similar entries for some major defensewide organizations, such as Special Operations Command and the military’s health care system. Each chapter 

also focuses on some special topics that are important for 

understanding the military’s force structure, such as the 

integration of different types of units or the military’s 

ability to conduct certain kinds of operations.

The structure of this report means that readers who are 

interested mainly in learning, for example, about the 

organization of the Marine Corps or the costs of an Air 

Force bomber squadron can, after reading Chapter 1, go 

straight to the relevant section.

CBO

CHAPTER

1

Introduction

For the first time in nearly two decades, the 

Department of Defense (DoD) has experienced 

sustained budget cuts in recent years: Annual appropriations (excluding additional appropriations for ongoing 

military operations) for 2013 through 2016 averaged 

about 5 percent less, in nominal terms, than the funding 

in 2012. The possible need to accommodate constraints 

on DoD’s budget in the future—because of caps on discretionary spending through 2021 enacted in the Budget 

Control Act of 2011, as amended—raises the question 

of how best to prioritize the various tasks that the department performs and how best to assess any proposed 

changes to the force. At the same time, the enormous 

size and complexity of DoD, the many specialized organizations it includes, the wide array of weapon systems and 

platforms it operates, and the complexity of its budget 

documents make the task of understanding how the 

department operates—and how its budget could be 

changed—daunting to many observers.

To increase policymakers’ understanding of the choices 

that the nation faces when considering DoD’s budget, the 

Congressional Budget Office has prepared this primer on 

the structure of the armed forces. There are many different ways to approach DoD’s budget; for the purposes of 

this analysis, CBO treats DoD as an organization that 

produces, sustains, and supports combat units. The number and type of combat units, as well as the personnel and 

equipment they contain, are referred to as the force structure. To produce this primer, CBO developed an analytic 

model of the military’s force structure in which DoD’s 

costs are viewed as inputs necessary to operate and sustain 

the force. The advantage of that treatment is that it provides a clear view of the trade-offs that would be involved 

if policymakers wanted to reduce DoD’s budget through 

cuts in the force structure—each element of the force 

structure has a cost associated with it, the costs of different elements can be compared, and it is possible to say 

how much of the force structure would have to be cut to 

generate a given amount of savings.

This primer contains entries that describe all of the major 

elements of the military’s force structure. Those elements 

include the major combat units that are the traditional 

backbone of the armed forces (such as armored brigades, 

aircraft carrier strike groups, and tactical aircraft squadrons). They also include specialized organizations that 

provide specific capabilities to DoD (such as specialoperations forces and missile defense). Each entry for 

a major element of the force structure provides the 

following information about that element: 

B CBO’s estimates of the number of military personnel 

and the costs associated with manning, operating, and 

sustaining a single unit of that type—what DoD refers 

to as operation and support (O&S) costs; 

B The number of such units that DoD has now and 

whether the department plans to change that number;

B Its intended function; 

B Its relative strengths and limitations; 

B Its use in past operations; and

B Common measures (when possible) of how many 

units of that type the United States might need. 

The primer also discusses some special topics that are 

important for understanding how DoD organizes and 

employs its forces but that are not specific to a single type 

of unit or do not have direct cost implications. Those discussions, which generally have a different format than the 

entries for major elements of the force structure, appear 

in the same chapter as the military service or types of 

units to which they most closely relate. (For example, the 

special topic of forcible-entry capability is discussed in 

the same chapter as Navy amphibious ships and Marine 

Corps battalions, since those are the forces used for 

amphibious assaults, the best-known form of forcibleentry operation.)
8 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

The primer concludes with three appendixes. The first, 

which is intended to serve as a quick reference, summarizes the size, costs, and number of each major element 

of the force structure included in CBO’s analysis. The 

second shows the relationship between DoD’s total O&S 

budget, the costs to operate and maintain each major 

element of the force structure, and the number and types 

of force structure elements in DoD’s current plans. The 

third is a brief summary of the military operations and 

DoD planning scenarios referred to in this report.

What Is Force Structure?

Although DoD has many responsibilities and functions, 

at the most basic level it is the organization responsible 

for manning, equipping, and training U.S. military 

forces.1

 The vast majority of DoD’s funding and personnel are assigned to tasks that contribute in some way to 

producing military forces that are prepared for combat. 

As such, DoD can be viewed as an organization that converts “inputs” of funding and personnel into “outputs” of 

combat capability, which are then available to be used as 

the nation sees fit.2

 That combat capability is best 

described in terms of the number and types of combat 

units that DoD can generate and sustain—that is, in 

terms of force structure.

Decisions about force structure strongly affect DoD’s 

costs, size, and capabilities, so force structure is generally 

central to any discussion of making large changes to 

DoD’s budget. Although the department has the ability 

to make some relatively small changes that do not affect 

its force structure, such changes usually have much more 

limited effects than changes in the force structure do. For 

example, the decision to field 11 aircraft carriers and their 

associated air wings and escort ships requires DoD to 

have a large number of military personnel, a large support 

infrastructure, fairly specific plans for shipbuilding and 

aircraft procurement, and so forth. When large cuts in 

DoD’s budget have been made in the past, they have 

almost always required reductions in the force structure.3

There is no generally agreed-upon way to measure combat capability directly and quantitatively. Force structure 

is the simplest and least subjective way to describe combat capability, although it has many limitations. The 

most significant drawback is that the concept of force 

structure inevitably invites “apples to oranges” comparisons, such as “how many aircraft carriers provide the 

same combat capability as an armored brigade?” More 

broadly, although having more combat units generally 

provides more combat capability, counts of the number 

of units available to the United States are not very useful 

if they do not consider the quality of those units. The 

same issue arises in any comparison of the force structures 

of different militaries: A U.S. armored brigade may have 

far more combat power (particularly when combined 

with its support units) than that of another country.

The full description of every element of the U.S. military’s force structure can be overwhelming. The exact 

number of units in the military varies with counting 

methods. As an example, however, the DoD databases 

that contain units’ reports about their readiness for combat include tens of thousands of units of thousands of different types. Thus, any widely useful description of the 

U.S. force structure requires some simplification.

For the purposes of this analysis, CBO divided all of 

DoD’s activities into three broad categories:

B Major Combat Units. These are the best known, 

most visible, and generally most important combat 

units in DoD’s inventory—such as Army brigade 

combat teams, Navy warships, and Air Force tactical 

fighter squadrons. In many instances, they are also 

the units of greatest interest to policymakers. For that 

reason, CBO organized this primer primarily as a 

discussion of major combat units. To show all important elements of the force structure, CBO presented 

some elements, such as special-operations forces, as if 

1. The actual use of those forces is also DoD’s responsibility. But 

DoD is organized in such a way that the administrative chain of 

command responsible for generating forces is largely separate 

from, and parallel to, the operational chain of command responsible for employing forces. In recent years, budgetary practices have 

maintained that separation: DoD’s “base” budget largely funds the 

administrative system for manning, equipping, and training units, 

whereas additional appropriations have been provided separately 

to fund ongoing military operations. 

2. That role is sometimes described as the “force provider” function, 

although DoD often uses that term in a more limited sense to 

refer to some of its subordinate organizations rather than to itself 

as a whole.

3. For a discussion of ways in which DoD might need to reduce the 

force structure to meet the spending restrictions of the Budget 

Control Act of 2011, see Congressional Budget Office, Approaches 

for Scaling Back the Defense Department’s Budget Plans (March 

2013), www.cbo.gov/publication/43997.
CHAPTER 1: INTRODUCTION THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 9

CBO

they were a single, large major combat unit, although 

they differ from traditional major combat units in 

numerous ways.

B Support Units. In the U.S. military, major combat 

units are employed alongside a vast number of units 

that support their activities in many different ways. In 

the Army, for example, brigade combat teams generally make up about one-third of the military personnel 

deployed to a combat theater—the other two-thirds 

are personnel assigned to units that are responsible for 

aviation, engineering, intelligence, civil affairs, ordnance, maintenance, transport, or other support services. Those additional units are essential for major 

combat units to accomplish their missions, but they 

are generally not the focus of discussions about the 

U.S. force structure. In this primer, every deployable 

combat unit in the U.S. inventory that is not classified 

as a major combat unit is considered a support unit. 

Across DoD as a whole, as many personnel are 

assigned to support units as to major combat units. 

(For a discussion of differences in how DoD and CBO 

use the term “support unit,” see Box 1-1.) 

B Administrative/Overhead Organizations. A large 

proportion of DoD’s military personnel, and almost 

all of the department’s 800,000 civilian personnel, are 

not assigned to deployable military units. Instead, they 

are part of various administrative or overhead organizations that perform key functions necessary for manning, equipping, and training combat and support 

units. Each military department has large administrative organizations devoted to such functions as recruiting, training, acquisition, maintenance, and medical 

care; in addition, there are various defensewide organizations that perform administrative or overhead functions for the entire military. In general, policymakers’ 

main concern with such functions is that they be performed efficiently, so as not to divert more resources 

than necessary from other activities. In this primer, 

all nondeployable portions of DoD (including those 

accounted for as “individuals,” such as trainees and 

other nondeployable personnel) are included in the 

administrative/overhead category.

That division into three types of activities allows CBO 

to further simplify its description of the U.S. force structure. Because some units support major combat units, 

and because DoD plans for such types of support in a 

predictable and regular way, the costs of the relevant support units can be considered part of the total cost of a 

major combat unit. That approach results in a package 

that CBO refers to as a “fully supported unit”—a major 

combat unit plus its support units. Similarly, because 

administrative or overhead activities are designed to help 

man, equip, and train units, and because DoD also plans 

for those activities in a predictable and regular way, a 

prorated amount of administrative/overhead costs can 

be considered part of the total cost of a fully supported 

unit.

Dividing DoD’s activities into those three categories also 

allows for a simple visualization of the department’s structure. Combat units are often described as representing the 

“tip of the spear” or having a “tooth-to-tail” ratio. Those 

metaphors capture an important point: A relatively small 

fraction (about one-third) of DoD’s personnel and budget are dedicated directly to major combat units. Like the 

metaphorical spear, those major combat units (the spear 

point) are supported by a large mass of support units and 

administrative organizations (the shaft of the spear). And 

just as the shaft is essential to a spear’s function as a 

weapon, DoD’s support units and administrative organizations are vital to the ability of major combat units to 

perform their roles.

Another distinction in the U.S. military is between a service’s active component (regular units belonging to the 

Army, Navy, Marine Corps, or Air Force) and the service’s 

reserve component (units belonging to the Army Reserve, 

Army National Guard, Navy Reserve, Marine Corps 

Reserve, Air Force Reserve, or Air National Guard). The 

services rely heavily on reserve-component units, which 

differ from active-component units in various ways, most 

notably in costs. For those reasons, CBO tried to display 

active- and reserve-component units separately in this 

primer whenever it was feasible to do so. However, 

because of the different way that each service integrates 

its reserve-component units into its overall structure, 

CBO was able to provide a meaningful division between 

active- and reserve-component units only for the Army 

and the Marine Corps. (The Navy Reserve has almost 

no units that fit the definition of major combat units 

used for this analysis, and the Air Force integrates its 

active- and reserve-component units so tightly that 

CBO could not readily separate the costs of the two 

components.)
10 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

How CBO Estimated the Costs of the 

Military’s Force Structure

The force structure model that CBO developed for this 

analysis is based on DoD’s fiscal year 2017 Future Years 

Defense Program (FYDP), which the department submitted to the Congress in April 2016 to provide detail for 

its 2017 budget request. The annual FYDP is a five-year 

plan that contains detailed information about DoD’s 

spending plans, distribution of personnel, and force 

structure for the budget year and the four subsequent 

years. 

CBO’s analysis focuses on operation and support costs, 

which make up about two-thirds of DoD’s “base” 

budget—the budget excluding separate appropriations 

provided to fund ongoing military operations. (The other 

one-third of that base budget is spent mainly on acquisition of weapon systems and on military construction and 

family housing.) O&S costs include compensation for 

military personnel, which is paid from the services’ military personnel accounts. O&S costs also include compensation for most civilian employees, health care costs for 

military and civilian personnel, and the expenses of running a unit (day-to-day operations, equipment maintenance, training, support contractors, and so on), all of 

which are paid from the services’ or defensewide operation and maintenance accounts. O&S costs are very 

closely related to the size of units—for instance, a unit 

with 10,000 military personnel will have military personnel costs commensurate with that size, and DoD has a 

limited ability to change those costs, particularly in the 

near term.

Box 1-1.

Defining Support Units

The Department of Defense (DoD) uses the word 

“support” in a wide variety of ways, and the term can 

have very different meanings in different contexts. To 

develop a clear and consistent framework for describing the military’s force structure in this primer, the 

Congressional Budget Office used DoD’s budget 

documents to develop rules for categorizing some of 

the department’s units as support units. Those rules, 

however, do not necessarily align with all of the ways 

in which DoD uses the term.

Broadly, “support” refers to the assistance that one 

unit or activity provides to another to help the second 

unit or activity accomplish its mission. DoD uses the 

general term that way in many contexts—some 

defense agencies are described as “supporting agencies,” some categorization systems employ the term to 

distinguish between types of units (such as the Army’s 

use of the categories “combat support” and “combat 

service support”), and various operational missions 

(such as “general support” or “direct support”) are 

colloquially described as support.

CBO’s definition of “support units” is intended to 

encompass the set of deployable units that would typically be assigned missions to support major combat 

units during an operation. In practice, almost any 

type of unit could be assigned to support almost 

any other type of unit. For example, during a U.S. 

deployment in Kosovo in 1999, plans called for 

ground units to support Army aircraft (by defending 

bases in Albania and using artillery to suppress Serbian air defenses), even though Army aircraft are typically assigned to support ground units. Thus, in 

actual operations, the line between a support unit 

and a unit being supported is dynamic—there are 

units that have been assigned support missions and 

units that receive support, but those designations 

are flexible, depending on the mission and the 

commander’s plans for accomplishing it.

For planning and budgeting purposes, however, military doctrine and administrative practice suggest that 

some types of units will typically be assigned to support other units. In most Army operations, for 

instance, brigade combat teams are the focus of 

ground combat operations, and most other units are 

assigned to support them, more or less directly. Similarly, in most Air Force operations, squadrons of 

combat aircraft are the focus of air operations, and 

most other units are assigned to support them in 

some fashion. In this primer, units such as brigade 

combat teams and combat aircraft squadrons are considered major combat units, and deployable units 

that provide support to them (however referred to by 

DoD) are considered support units. 
CHAPTER 1: INTRODUCTION THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 11

CBO

For this analysis, CBO divided O&S costs into three categories: direct, indirect, and overhead costs. Those groupings match the three categories that CBO used for DoD’s 

units and activities: Direct costs are associated with major 

combat units, indirect costs with support units, and overhead costs with administrative or overhead organizations. 

CBO also used the direct, indirect, and overhead categories for the number of military personnel associated with 

a unit. That breakdown, for both costs and personnel, is 

shown in the table that accompanies each entry in this 

primer for a major element of the force structure. 

Direct Costs

For most major combat units, the FYDP includes entries 

that show DoD’s total costs for a unit of that type and the 

total number of military personnel assigned to that kind 

of unit. The numbers for direct costs (the costs of a major 

combat unit itself) and direct personnel (the personnel 

assigned to the unit itself) are annual averages of the five 

years of numbers shown in the FYDP. In the case of costs, 

those averages are in 2017 dollars.4

 Direct costs also 

include a share of the costs of the Defense Health Program 

(DHP) that is based on the number and type of military 

personnel in the major combat unit.

Indirect Costs

To determine which units should be classified as providing support to major combat units for the purposes of 

this analysis, CBO used a variety of sources, including its 

past studies, DoD databases, and military doctrine. In 

general, ground forces (such as those of the Army and 

Marine Corps) have a fairly direct relationship between 

combat and support units that can be readily identified 

and described. With naval and air forces, however, those 

relationships are much less well defined and are more difficult to characterize. For example, naval and air forces 

require large numbers of higher-level maintenance units, 

which may support many different types of combat units. 

In the absence of details about the actual workload of such 

maintenance units, CBO made simplifying assumptions 

about the likely distribution of that workload among different types of combat units. Ground forces are more 

likely to have maintenance shops assigned to specific 

units (such as the Marine logistics group that is assigned 

to each Marine expeditionary force), so fewer simplifying 

assumptions were necessary.

Once the process of ascribing support units to combat 

units was finished, each type of major combat unit had a 

set of associated support units that should reflect the 

additional units that DoD would probably create or disband if it created or disbanded a major combat unit of 

that type.5

 With that set of units defined, CBO was able 

to use information from the FYDP to estimate indirect 

costs and personnel counts associated with that set of 

support units in the same way that it estimated direct 

costs and personnel numbers for major combat units. As 

with direct costs, CBO included a fraction of the DHP’s 

costs based on the number and type of military personnel 

in the set of support units.

Overhead Costs

For administrative or overhead organizations, CBO 

determined that the majority of those organizations’ 

workload is essentially dependent on the size of the 

force—for instance, a larger force requires more recruiters 

to find more recruits, more trainers to train those recruits, 

and more doctors to provide medical care. Some workload (such as that of maintenance depots) is driven by the 

amount of equipment in the force, but the amount of 

equipment is itself largely tied to the size of the force. 

Thus, for the majority of each service’s administrative or 

overhead organizations, CBO assigned prorated fractions 

of those organizations’ costs and personnel—referred to 

here as overhead—to the costs and personnel of each fully 

supported combat unit. For example, if a fully supported 

combat unit accounts for 2 percent of the personnel that 

a service devotes to major combat and support units, it is 

4. Because the FYDP covers a five-year period and because, in many 

cases, the number of planned forces changes over that period, 

CBO calculates costs for a major combat unit by dividing the total 

five-year constant-dollar cost for that type of unit by the total fiveyear count of such units. That approach means that the estimate 

of costs is also an average over time. O&S costs generally rise over 

the years (because of pay raises, increases in health care costs, and 

other factors), so the costs that CBO estimates in this analysis are 

slightly higher than those in the FYDP earlier in the five-year period 

and slightly lower than those in the FYDP later in the period.

5. In some cases, the set of support units that CBO ascribed to a 

major combat unit would only approximate the changes that 

DoD would probably make if it added or eliminated a combat 

unit. For example, CBO considered an Army corps headquarters 

to be a type of support unit, but each corps headquarters would be 

expected to command a large number of brigade combat teams 

(BCTs). Thus, CBO assigned each BCT a fraction of a corps 

headquarters as a part of its support units. In practice, however, 

DoD would not eliminate a fraction of a corps headquarters if it 

disbanded a BCT; it would probably alter the number of corps 

headquarters only if it made large changes to the size of the Army. 
12 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

assumed to require 2 percent of the service’s administrative and overhead organizations to sustain it. 

CBO also assigned to each type of fully supported combat unit a prorated fraction of the costs and personnel of 

defensewide agencies, such as the Defense Finance and 

Accounting Services agency, which provides payment services to DoD. Finally, as with direct and indirect costs, 

CBO included a share of the costs of the DHP based 

on the number and type of military personnel in an 

administrative or overhead organization.

Other Considerations

Some activities of the individual services or DoD as a 

whole do not fit easily into that analytic framework. 

Thus, for each military department, this primer includes 

an “Other Activities” component, which CBO treats like 

a major combat unit (because those activities cannot be 

considered support or overhead for another type of major 

combat unit). Such activities include a service’s specialoperations forces, some of its command-and-control 

activities, its construction engineers, and so forth. 

In a similar fashion, CBO describes separately the costs of 

defensewide activities that cannot be categorized as support or overhead for major combat units, such as health 

care costs for military retirees—one of the few categories 

of O&S costs in this primer that CBO considered to be 

independent of decisions about the future size of the 

force. (For a discussion of CBO’s approach to judging 

which costs depend on the size of the force and which are 

independent of that size, see Box 1-2 on page 14.) The 

end result accounts for the entirety of DoD’s O&S budget—there are no activities, funding, or personnel that 

are not included in this analysis.

Because CBO’s force structure model is based on the 

2017 FYDP, its estimates of the costs of major combat 

units, support units, and administrative and overhead 

activities are the amounts that DoD estimated those units 

would cost over the five-year period covered by the 2017 

FYDP, not what they should or could cost. As a result, if 

DoD underestimated or overestimated the costs of certain support activities in its five-year plan, CBO’s estimates in this report will reflect that. Similarly, every 

FYDP reflects the implications of DoD’s choices about 

how to direct its resources toward such goals as improving 

units’ readiness for combat, compensating personnel, or 

manning units. CBO’s analysis did not explore alternative 

scenarios for how to choose among those goals.6

How Changes in the Force Structure 

Would Affect Costs

Typically, DoD proposes changes in the force structure in 

its budget requests, and the Congress approves them or 

directs DoD to alter them. If the Congress wished to 

change the military’s force structure in a manner independent of DoD’s requests, it could use several available 

tools. 

First, it could codify the force structure in law (as it did in 

section 5063 of the U.S. Code, which requires the Marine 

Corps to maintain at least three divisions and three air 

wings). Second, because the Congress is responsible for 

authorizing the total number of military personnel that 

each service maintains (the end-strength authorization), 

it could choose to authorize an end strength other than 

what DoD requests. Third, the Congress could bar DoD 

from using any funding to implement changes to the 

force structure of which it does not approve. (The Congress has used that power in recent years—for example, to 

prohibit the Air Force from retiring A-10 aircraft despite 

the service’s repeated requests to do so.) Such Congressional actions would have a more rapid impact on the costs 

of U.S. forces than changes made through DoD’s decisionmaking process would. For instance, if the defense 

authorization act for any fiscal year included a new endstrength authorization, DoD would be obligated to try to 

achieve that new end strength in the same fiscal year.

The effect on DoD’s budget of cutting or adding forces 

would depend on how the changes were made. In the case 

of reducing the force structure, for example, eliminating a 

major combat unit would, at a minimum, eliminate 

within a few years the direct costs of operating that unit. 

If DoD was able to eliminate the unit’s associated support 

units, it would also save the costs of operating those units 

within a few years of deciding to do so. In addition, if 

DoD was able to trim the share of administrative and 

overhead activities associated with the major combat unit 

and its support units, the department could remove those 

costs as well—thus eliminating the total costs that CBO 

attributes to the fully supported major combat unit. 

Historical evidence and other considerations suggest that 

DoD would make those associated cuts over several years. 

6. Other CBO analyses have, for example, shown that DoD is planning to spend significantly more per service member to support its 

forces than it did before the conflicts in Iraq and Afghanistan or 

than historical trends would suggest. See Congressional Budget 

Office, Long-Term Implications of the 2016 Future Years Defense 

Program (January 2016), www.cbo.gov/publication/51050.
CHAPTER 1: INTRODUCTION THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 13

CBO

In the case of adding a major combat unit, direct, indirect, and overhead costs would change in the opposite 

direction, and the same considerations would apply.

In many instances, DoD’s internal decisionmaking processes do not explicitly link major combat units with their 

support units and their administrative and overhead 

costs. Thus, DoD would have to make several separate 

decisions to bring about all of the changes that CBO 

projects could flow from the single decision to eliminate a 

major combat unit. Because of the great complexity of 

the force structure and the many roles that different types 

of units play, that sequential decisionmaking process gives 

ample opportunity for concerned parties within DoD to 

argue against a commensurate reduction in support units 

or administrative and overhead activities. For example, 

DoD frequently changes the mix of support units in the 

force, and a proposed reduction in a support activity 

often provokes discussion about whether that form of 

support has become more useful over time and thus 

should be protected from a planned cut. 

In other cases, the size of a support or administrative 

activity may be based on several different missions, and 

cuts that reduce the need for one mission may not allow 

proportionate cuts in that activity because of the requirements of the other missions. For instance, the Air Force’s 

fleet of bombers is intended to be able to conduct both 

conventional (nonnuclear) and nuclear bombing missions. If DoD wanted to keep its current conventional 

bombing capability but decrease the bomber portion of 

its nuclear deterrent, reductions in the bomber fleet based 

on nuclear bombing capability could be limited by the 

need to maintain the current amount of conventional 

bombing capability.

The range of costs that CBO attributes to each unit in 

this report can be thought of as representing the range of 

effects of making a change in the force structure. The 

direct cost alone should represent a lower bound for costs 

or savings, whereas the total costs should represent an 

upper bound for costs or savings that would be achievable 

if DoD and the Congress made the associated changes in 

indirect and overhead costs.

Once decided on, any large changes to the military’s force 

structure would take a number of years to implement. In 

general, adding or eliminating major combat units 

appears to take DoD about three to five years, so savings 

from reducing forces would not appear immediately. 

Moreover, the separate decisions that would be required 

to reduce support units or administrative and overhead 

activities might occur in subsequent rounds of decisionmaking, so the savings associated with reducing those 

activities might take even longer to materialize fully.7

During the military drawdown that occurred in the early 

1990s, DoD’s cuts in overhead activities lagged behind 

cuts in forces by several years, and savings took more than 

five years to be fully realized.

Other policy choices would also affect the costs or savings 

that would result from changes in the size of the force. 

Those choices include decisions about the pay and 

benefits of DoD’s personnel, the degree to which units 

are kept at full strength, the type of units considered 

necessary to support major combat units, and the 

preferred balance to strike in relying on active- versus 

reserve-component units.8

 For the purposes of this 

analysis, CBO examined only the effects of changes to the 

size and composition of the force structure, assuming that 

all other policy factors would remain unchanged. That 

simplifying assumption, although useful for isolating the 

effects of a single type of policy choice, would not necessarily be true for all proposals to change the military’s 

forces—it is likely that several related policy decisions 

would be made at the same time. (For example, in its 

2015 budget submission, the Army proposed both to 

reduce the size of its forces and to change how it assigns 

aviation units to its active and reserve components.)

7. Because DoD does not mechanically link decisions about all of the 

elements of the force structure together, the sheer number of different decisions, and the unique considerations relating to each 

type of unit, might make it difficult or impossible for DoD to 

make all of the relevant decisions during a single budget cycle. For 

example, in recent years, the Army’s plans in the FYDP included a 

“negative wedge” of funding intended to represent the difference 

between DoD’s plans for the Army’s funding and the costs of the 

Army’s planned structure. That wedge existed because the Army 

required several budget cycles to decide on the full details of how 

it would draw down its forces to a smaller size.

8. The cost of pay and benefits for military personnel is a key factor 

in the long-term affordability of the armed forces, accounting for 

about one-third of DoD’s budget. Military compensation has 

been the focus of substantial public discussion and numerous 

policy proposals. See, for example, Congressional Budget Office, 

Costs of Military Pay and Benefits in the Defense Budget (November 

2012), www.cbo.gov/publication/43574, and Approaches to Reducing Federal Spending on Military Health Care (January 2014), 

www.cbo.gov/publication/44993. This primer reflects DoD’s 

plans as recorded in the 2017 FYDP, which do not include any 

changes to current compensation policies.
14 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Continued

Box 1-2.

Why CBO Projects That Most of DoD’s Operation and Support Costs Are Proportional to the 

Force Structure

One of the issues that the Congressional Budget 

Office faced in conducting this analysis was determining which of the Department of Defense’s 

(DoD’s) costs depend on the size of the force and 

which are independent of that size. In this analysis, 

CBO treats virtually all of DoD’s operation and support (O&S) funding and personnel as costs of sustaining the military’s force structure. In that view, 

costs that are unrelated to the size of the force (called 

independent costs, or fixed costs) make up a very 

small portion of the O&S budget; the only truly 

independent expense to DoD is health care costs for 

retired military personnel. Instead, the O&S budget 

is considered to consist almost entirely of costs that 

depend on the size of the force (sometimes called 

variable costs)—meaning that if the force structure 

was cut by 10 percent, for example, DoD’s O&S 

costs would decline by almost 10 percent. 

Several factors contributed to CBO’s decision to treat 

nearly all of the O&S budget as dependent on the 

size of the force:

B Most of the activities funded by that budget could 

be affected by future policy choices; 

B Few activities that might be considered independent costs are significant in size; and 

B Historically, large changes in DoD’s budget have 

eventually affected most of the department’s 

activities. 

Consequently, CBO projects that a large change in 

the force structure would, after several years, alter 

almost all of DoD’s operation and support accounts, 

aside from health care costs for retirees.1

CBO’s approach is based on the view that some 

important DoD activities that might be considered 

fixed costs are actually the result of policy choices. 

For example, it is common to treat “maintaining the 

U.S. nuclear deterrent” as a fixed operating cost for 

DoD, for several reasons: That activity is fairly 

straightforward and generally proceeds with stable 

funding year after year; it produces a valuable, if 

hard-to-measure, source of defense (“deterrence”); the 

need for such deterrence is essentially constant; and 

the activity can easily be treated as a flat charge to 

DoD in analytic frameworks. However, the size of the 

U.S. nuclear deterrent is not fixed; it can easily be 

changed by policymakers and has been many times in 

the past. Similarly, although such things as the size of 

special-operations forces or the amount of resources 

invested in command and intelligence activities are 

easy to treat as fixed costs, they represent separate and 

meaningful policy choices about the size of specialoperations forces or about how many resources 

should be devoted to command and control or intelligence. By treating those activities as changeable, 

CBO greatly reduced the scope of costs that are 

considered fixed costs.

The DoD activities that are classic examples of fixed 

O&S costs tend to be small. The military departments’ administrative and overhead costs are dominated by personnel commands, training commands, 

and medical commands, the size of which is largely 

determined by the overall number of personnel in the 

force, as well as by equipment commands, the size of 

which is indirectly determined by the number of personnel (since more personnel generally require more 

equipment). Similarly, the cost of defensewide activities stems mainly from providing current military 

personnel or their families with various services, such 

as health care, commissaries and exchanges, schools 

for dependent children, payroll services, and 

1. Health care costs for current military retirees reflect the cost 

of fulfilling obligations that the United States has already 

incurred (when those service members were employed by 

DoD). As such, those costs do not depend on the size of 

future forces. Pensions and other payments to current military retirees are also independent of the size of future forces, 

but they do not appear in DoD’s budget. Those payments 

are made from a mandatory account administered by the 

Treasury Department rather than from DoD’s current 

appropriations.
CHAPTER 1: INTRODUCTION THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 15

CBO

Costs Not Included in This Analysis

CBO’s analysis addresses operation and support costs for 

major combat units. Therefore, it does not include acquisition costs (for the development and purchase of major 

weapon systems, as well as upgrades to existing systems) 

or construction costs (for infrastructure such as buildings 

and housing at military installations). Those costs are 

significant, together making up almost one-third of 

DoD’s total base budget (excluding appropriations to 

fund ongoing military operations). 

Whereas O&S costs are tightly linked to the size of the 

force, DoD and lawmakers have substantial discretion 

over acquisition and construction costs. The size of the 

force structure does not necessarily determine the 

appropriate size of the budgets for weapon systems or 

infrastructure. For example, regardless of how many 

fighter squadrons the Air Force maintains, it faces separate choices about whether to purchase new advanced 

fighter aircraft, upgrade existing aircraft, or keep the current fleet of aircraft. 

In many cases, if DoD chose to add units to the force 

structure, there would be predictable effects on acquisition and infrastructure costs, because DoD would need 

to purchase additional equipment or construct additional 

facilities for the new units. If, however, DoD eliminated 

units in the near future, savings in acquisition and 

Box 1-2. Continued

Why CBO Projects That Most of DoD’s Operation and Support Costs Are Proportional to the 

Force Structure

telecommunications services. The costs of all of those 

services depend on the total number of personnel. 

Defensewide activities whose size is largely independent of the number of personnel—such as cooperative security arrangements, the acquisition workforce, 

or the recovery of remains of personnel missing in 

action—make up a tiny proportion of the defensewide O&S budget.1

 According to DoD’s budget documents, about 60 percent of O&S funding for 

administrative organizations goes for central logistics, 

medical care, personnel administration, personnel 

benefits, and training; another 20 percent represents 

costs for military installations. All of those activities 

scale with the size of the force structure, in CBO’s 

view. 

Finally, when the overall defense budget has been cut 

in the past, most parts of DoD’s budget have 

declined. One reason is the practice of “top-down” 

budget management. For example, if fiscal pressures 

required DoD to reduce its budget by 5 percent, it 

might cut the budgets of most of its organizations by 

5 percent. Such a step is feasible because many activities that are cited as classic examples of DoD’s independent costs are not truly independent of DoD’s 

workload and can be trimmed with sufficient attention from management. 

In the case of military bases, for instance, removing a 

small number of forces from a base will not cause the 

base to be closed, which can make the costs of operating bases appear largely independent of the number 

of military forces that DoD maintains. But many 

costs of operating a base can vary proportionally with 

the size of the force at smaller scales. For example, if a 

base loses half of its units, DoD can trim contracts 

for cafeteria services and maintenance, pay less for 

utilities, and so forth. At larger scales, major changes 

in the force structure have historically triggered base 

closures and consolidations, eliminating those operating costs. Thus, such costs are somewhat variable at 

small scales but are fully variable at larger scales over a 

number of years, if DoD or lawmakers decide to cut 

them. 

Because DoD does not have the authority to close 

bases by itself, and the Congress has traditionally 

exercised a high degree of control over the base closure process, DoD tends to perceive the costs of operating bases as independent of its policy choices. For 

the Congress, however, such costs are indeed variable—lawmakers can change the number of bases just 

as they can alter any other aspect of DoD’s size or 

funding, although the actual base closure process is 

time-consuming and potentially controversial.

1. Most of DoD’s acquisition workforce is funded through 

acquisition accounts, which increase or decrease largely on 

the basis of DoD’s acquisition plans.
16 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

infrastructure costs would be much harder to predict. 

One reason is that many of DoD’s plans to acquire new 

weapon systems do not include enough purchases to 

replace all of the older models in the current force. A 

smaller force might allow DoD to scale back planned 

purchases of such weapon systems, or it could just as 

easily allow DoD to use the same funding to replace all 

of the older models with newer ones.

In some cases, the amount of detail in CBO’s model is 

limited by the way in which DoD categorizes activities in 

discrete chunks, called program elements, for the Future 

Years Defense Program. For example, the FYDP does not 

distinguish between Navy squadrons that have different 

types of fighter aircraft, using the same program element 

for squadrons equipped with older F/A-18C/D aircraft 

and for those equipped with newer F/A-18E/F aircraft. 

Thus, the FYDP does not provide any direct information 

for separating the costs of F/A-18C/D squadrons from 

those of F/A-18E/F squadrons. When possible, CBO 

tried to work around those shortcomings by using supplementary information, such as databases maintained by 

the services that include operating costs for different 

weapon systems. But making such distinctions was not 

always possible (including in the case of the Navy’s fighter 

squadrons). Limits on information were usually greatest 

in the case of weapon systems that have not yet been 

introduced (such as the F-35 Joint Strike Fighter), 

because the services often lack essential details about 

actual operating costs.

Guide to Reading This Report

This primer is designed to be a reference work with discrete entries, so it does not need to be read in a linear 

fashion. A reader who is interested in the structure of 

the Air Force or the costs of the Army’s infantry brigade 

combat teams can flip to the relevant section. 

The next three chapters focus on the Departments of the 

Army, the Navy (including the Marine Corps), and the 

Air Force. The last chapter focuses on defensewide organizations within DoD that are not part of those departments. Each of the chapters has the same basic structure:

B The chapter begins with an introduction to the military department in question (or to defensewide activities) that describes the size of the department; the 

types of major combat units it provides; the way it 

typically organizes those combat units with their 

support units; the distribution of its personnel among 

direct, indirect, and overhead functions; and the relationship between units in the active and reserve components. The introduction also briefly discusses the 

strengths and limitations of the department’s overall 

forces.

B The majority of the chapter consists of individual 

entries for each type of major combat unit (or defensewide organization). Those entries cover the costs and 

personnel (direct, indirect, and overhead) associated 

with a given type of unit, the number of such units in 

DoD’s current and planned forces, the purpose and 

limitations of that type of unit, and the units’ past and 

planned use in operations.

B The chapter concludes with entries about topics that 

are of special interest to a particular department or to 

DoD as a whole. Those special topics cover activities 

that do not represent separate costs but that are nonetheless important for understanding the military’s 

force structure. For example, Chapter 4 includes separate entries that show the costs and personnel required 

for the Air Force’s squadrons of tactical aircraft, bombers, and unmanned air systems as types of major combat units. The chapter also includes a special-topic 

entry about the military’s strike capability (the ability 

to destroy a wide variety of enemy targets rather than a 

few specific types), which is provided in part by tactical aircraft, bombers, and unmanned air systems. In 

that example, strike capability is not a type of major 

combat unit or a separate cost, but DoD’s desire to be 

able to carry out strike missions is crucial to understanding why the Air Force maintains the set of 

combat units that it does.

Following the chapters, Appendix A provides an overview 

of the total cost and personnel required for each type of 

major combat unit, as well as the number of those units 

that DoD plans to maintain in each year of the 2017–

2021 period covered by the 2017 FYDP. Appendix B 

shows how the costs and personnel counts for each type 

of major combat unit, as estimated by CBO, sum to the 

totals for DoD’s operation and support budget and military personnel reported in the 2017 FYDP. Finally, 

Appendix C summarizes the past military operations and 

current planning scenarios referred to in this report, with 

a focus on the types of forces used in each one.
CBO

CHAPTER

2

Department of the Army

Overview

The Department of the Army includes the Army’s active 

component; the two parts of its reserve component, the 

Army Reserve and the Army National Guard; and all 

federal civilians employed by the service. By number of 

military personnel, the Department of the Army is the 

biggest of the military departments. It also has the largest 

operation and support (O&S) budget. The Army does 

not have the largest total budget, however, because it 

receives significantly less funding to develop and acquire 

weapon systems than the other military departments do.

The Army is responsible for providing the bulk of U.S. 

ground combat forces. To that end, the service is organized primarily around brigade combat teams (BCTs)—

large combined-arms formations that are designed to 

contain 4,400 to 4,700 soldiers apiece and include infantry, artillery, engineering, and other types of units.1

 The 

Army has 30 BCTs in the active component and 26 in 

the National Guard (there are none in the Army Reserve). 

It has no plans to change those numbers over the next five 

years (see Table 2-1). The vast majority of the Army’s 

support units exist to support combat operations by 

BCTs, and the vast majority of the Army’s administrative 

units exist to create, train, and maintain BCTs and their 

support units.2

The current organization of the Army into BCTs is a 

change from historical practice. Before the mid-2000s, 

when the service launched a “modularity” initiative, the 

Army was organized for nearly a century around divisions 

(which involved fewer but larger formations, with 12,000 

to 18,000 soldiers apiece). During that period, units in 

Army divisions could be separated into ad hoc BCTs 

(typically, three BCTs per division), but those units were 

generally not organized to operate independently at any 

command level below the division. (For a description of 

the Army’s command levels, see Box 2-1.) In the current 

structure, BCTs are permanently organized for independent operations, and division headquarters exist to provide command and control for operations that involve 

multiple BCTs.

The Army is distinct not only for the number of ground 

combat forces it can provide but also for the large number of armored vehicles in its inventory and for the wide 

array of support units it contains. Those support units 

include units with significant firepower, such as artillery 

brigades (which have missile launchers as well as traditional cannon artillery), aviation brigades (which have 

attack, reconnaissance, utility, or cargo helicopters), and 

other combat arms (such as Patriot missile launchers to 

defend against other missiles and aircraft). Army support 

units include many other types of specialized units, such 

as construction engineers, military intelligence, military 

police, and the Army’s extensive logistics apparatus. 

Many of those types of units are responsible for supporting not just Army units in the field but all of the other 

services in a combat operation. For example, the Army 

is generally responsible for all theater logistics functions, 

port operations, and enemy prisoner-of-war detention 

operations.

Besides those combat and support units, the Army contains a number of smaller organizations that provide 

niche capabilities unrelated to BCTs. Two noteworthy 

examples are the Army’s special-operations forces (units 

such as the 75th Ranger Regiment, the 160th Special 

Operations Aviation Regiment, and the seven Special 

Forces Groups), and the Army’s responsibility for 

1. Formations, such as BCTs, that contain a mix of different types 

of units are referred to as combined arms. Such formations offer 

advantages over homogenous formations because the different 

types of units can complement one another and help offset the 

limitations of any single type of unit. Although all BCTs include 

a mix of unit types, it is customary to refer to them by their 

predominant type of combat unit.

2. As noted in Chapter 1, “support” can have a wide variety of meanings in the military, and whether a unit is generally considered a 

combat unit or a support unit does not mean that it always plays 

that role in a particular operation. For more details, see Box 1-1 

on page 10.
18 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table 2-1.

Number of Major Combat Units in the Army, 

2017 and 2021

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

operating the Ground-Based Midcourse Defense portion 

of the national missile defense system (both of which are 

discussed in Chapter 5).

Distribution of Army Personnel

Of the nearly 1 million military personnel serving in the 

Army as a whole, roughly half are in support units and a 

third are in combat units (see Table 2-2). The rest belong 

to units that perform various overhead functions, such as 

recruiting, training, and equipping combat units. The 

Army’s reserve component is slightly larger than its 

active component, with 54 percent of the service’s total 

personnel.

Since the 1970s, the Army has interpreted the Department of Defense’s Total Force Policy—which involves 

treating a service’s various components as a single force—

by concentrating combat units in the active component 

and support units in the reserve component. Over the 

2017–2021 period, the Army plans to have an average of 

59 percent of its combat personnel in the active component and 75 percent of its support personnel in the 

reserve component. The practical effect of that distribution is that the Army has enough support units in its 

active component to conduct relatively small operations 

on its own, but larger combat operations usually require 

it to mobilize a significant number of reservists to provide 

support for the active-component combat units—as 

occurred during the occupation of Iraq. (For more discussion of the implications of that structure, see the specialtopic entry about integration of the Army’s active and 

reserve components on page 38.)

Command Levels and Units

The Army’s combat units are organized in a recursive 

pattern: A unit at any command level contains two to five 

subordinate units of a similar type, plus additional supporting units. For example, an infantry brigade has two or 

three infantry battalions, a cavalry squadron, and a single 

battalion each of special troops, artillery, engineers, and 

logistics.3

 Similarly, an infantry battalion has three infantry companies, a heavy weapons company, and a headquarters company. That pattern is repeated at lower levels 

(a company consists of platoons, and platoons consist of 

squads) and at higher levels (a division consists of brigade 

combat teams, and a corps consists of divisions), as 

detailed in Box 2-1. However, some command levels have 

different names depending on the type of unit; for 

instance, cavalry squadrons are at the same command 

level as infantry battalions.

This analysis treats supporting units as directly connected 

to combat units in a fixed relationship, but that treatment 

is an approximation that is valid only when discussing 

force planning. In actual operations, most support units 

are assigned to higher command levels, which give them 

specific missions. A BCT does not include the support 

units that the Congressional Budget Office attributes to 

it in this analysis—those units are division-, corps-, or 

theater-level assets that would be deployed to support the 

BCT and without which the BCT could not function. 

Furthermore, although the Army’s plans involve maintaining a given set of units in the force structure, the 

commander of a specific operation can, and often does, 

tailor the mix of support units that are deployed to suit 

the circumstances of a particular theater of operations. 

For example, during the occupation of Iraq, the Army 

generally did not deploy artillery or air-defense units, 

although it had them in its force structure. Such units 

were considered unnecessary in that operation, and some 

were converted to perform roles deemed more useful during the occupation, such as protecting supply convoys.

9 9

5 5

7 7

2 2

14 14

19 19

Total Brigade Combat Teams

Active component 30 30

National Guard 26 26

National Guard

Infantry Brigade Combat Teams

Active component

National Guard

Stryker Brigade Combat Teams

2021

Armored Brigade Combat Teams

Active component

National Guard

Active component

2017

3. Cavalry units are units that perform the same armed reconnaissance role once carried out by troops on horseback. Today, 

cavalry units are equipped with helicopters, tanks, armored 

fighting vehicles, or wheeled vehicles.
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 19

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Historically, ground combat units have been classified 

using weight-related terms, which reflect the weight of 

the units’ equipment and their commensurate speed and 

ability to maneuver. For decades, the Army broadly classified its forces in that way: Armored and mechanized 

infantry units, which had the heaviest armored vehicles, 

were considered “heavy” forces, whereas infantry, 

air-assault, and airborne units, which had only a few or 

no armored vehicles, were considered “light” forces. 

Today, the Army has three types of brigade combat teams, 

which are roughly analogous to heavy, medium, and light 

forces—armored BCTs have large numbers of the heaviest armored vehicles, Stryker BCTs have large numbers of

Box 2-1.

Command Levels of U.S. Ground Forces

The Army and Marine Corps are generally organized 

as hierarchies of units, with each type of unit commanded by a noncommissioned or commissioned 

officer of a specific rank. (Officers of other ranks play 

essential roles in those units but typically do not 

command them.) Those units are described here 

from smallest to largest:

Squad/Section: A squad is commanded by a sergeant 

and has 4 to 12 personnel. A section is a group of 

vehicles, generally two in number.

Platoon: A platoon is commanded by a second lieutenant and includes varying numbers of subordinate 

squads or sections. It has 16 to 50 personnel. Heavy 

platoons have four armored vehicles (such as tanks or 

infantry fighting vehicles, depending on the type of 

platoon).

Company/Troop/Battery: A company is commanded by a captain and includes two to five 

subordinate platoons (usually three or four). It has 

about 60 to 200 personnel. Heavy companies have 

14 armored vehicles. Cavalry companies are called 

troops; artillery companies are called batteries.

Battalion/Squadron: A battalion is commanded by a 

lieutenant colonel and usually includes three to five 

combat companies and one support company. It has 

about 400 to 1,000 personnel. Heavy battalions have 

58 armored vehicles. Cavalry battalions are called 

squadrons.

Brigade Combat Team/Functional Support 

Brigade/Regiment/Group: A brigade is commanded 

by a colonel and is generally configured as either a 

brigade combat team (BCT) or a functional support 

brigade (FSB). A BCT has about 4,400 to 4,700 personnel, depending on whether it is an armored, 

Stryker, or infantry BCT. An FSB has about 3,000 

to 5,000 personnel, depending on its type (of which 

there are 20). Cavalry brigades are called regiments; 

some types of support brigades are called groups. 

Marine Corps units at this level are also called regiments. (The term “Marine expeditionary brigade” 

refers to a task force, which is larger.)

Division: A division is commanded by a major general and includes two to five BCTs (usually four), an 

aviation brigade, an artillery brigade, an engineer 

brigade, and a logistics brigade. Divisions have about 

12,000 to 16,000 personnel.

Corps: A corps is commanded by a lieutenant general 

and includes two to five divisions and numerous 

support brigades and commands. Corps have about 

40,000 to 100,000 personnel. The Marine Corps 

does not have corps, although a Marine expeditionary 

force is similar in size and is also commanded by a 

lieutenant general.

Army: An army is the highest command level in a 

given theater of operations and typically has 100,000 

to 300,000 personnel. It is an element of a joint 

command structure—the Army’s component is 

commanded by a general. An operational theater is 

established to support one or more corps (usually 

two) and includes numerous support brigades and 

support commands. (The term “theater” is also used 

frequently, including in this primer, to refer to the 

area in which a military operation takes place.)
20 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table 2-2.

Average Distribution of the Department of the 

Army’s Military Personnel, 2017 to 2021

Number of Personnel

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

Numbers may not add up to totals because of rounding.

a. “Overhead” refers to administrative units as well as to personnel not 

assigned to any unit.

lightly armored vehicles (called Stryker vehicles), and 

infantry BCTs have few armored vehicles.4

 The Army 

maintains a mix of BCTs so it can use the type of unit 

most appropriate for a given military operation.

A possible source of confusion when discussing Army 

units is that although combat units generally have a fixed 

set of subordinate units assigned to them, many support 

units do not have such a fixed composition. Instead, they 

are intended to have units assigned to them as the need 

arises.5

 For example, a combat brigade typically has more 

than 4,000 personnel assigned to it, but a support brigade 

might have only about 100 personnel. That difference 

does not indicate a large variation in size between the two 

types of brigades; rather, it reflects the fact that the support 

brigade does not have permanently assigned subordinate 

units. (Support brigades are perhaps better thought of as 

brigade headquarters, which are company-size units of 

about 100 personnel that provide command and control 

for subordinate support units.) Thus, it is important to 

note whether a given Army unit includes or does not 

include subordinate units. Similarly, descriptions of the 

total number of brigades in the Army can be misleading 

because of differences between BCTs and other types of 

brigades.

Another possible source of confusion involves differing 

ways to count the number of personnel in a unit. The size 

and organization of Army units is based on an official template, the Army’s Table of Organization and Equipment 

for that type of unit. However, actual Army units do not 

always conform to their template for a variety of reasons—

they may not include all of the subordinate organizations, 

they may be manned at a higher or lower level than 

100 percent, or they may be transitioning from one template to another. (In recent years, for example, the Army 

has transitioned many of its BCTs from an older template, 

with two subordinate maneuver battalions, to the current 

design, with three subordinate maneuver battalions.) 

When discussing the size of BCTs, this report uses the 

personnel numbers in the Army’s official templates. For the 

aforementioned reasons, those numbers sometimes differ 

from the personnel numbers shown in the tables in this 

report, which are five-year averages based on the plans 

underlying DoD’s 2017 budget request. 

Strengths and Limitations of Army Forces

Although each type of BCT has its own strengths and 

weaknesses, the Army’s ground forces overall are exceptionally powerful combat units that are generally considered capable of defeating any conventional ground 

forces—such as other national armies—that they might 

be expected to fight. The United States has not suffered a 

serious defeat from other conventional ground forces 

since 1950, when the Chinese military intervened in the 

Korean War. Since then, the U.S. Army has consistently 

been able to overwhelm opponents who have attempted 

conventional operations against it. (Its record is less clearcut in unconventional warfare, as discussed below.) 

The use of ground forces is generally thought to represent 

a high level of military commitment for the United 

States. In the past, the U.S. military has typically been 

able to achieve more ambitious goals in conflicts that 

have involved large Army deployments than in conflicts 

in which the U.S. commitment was limited to air and 

naval strikes. Ground forces were considered essential to 

the defense of South Korea in the 1950s, the liberation of 

Kuwait in 1991, and the overthrow of the Iraqi and 

Afghan governments in the 2000s. Although U.S. efforts 

to defend South Vietnam in the 1960s and 1970s were 

ultimately unsuccessful, conventional operations by the 

North Vietnamese to conquer South Vietnam did not 

succeed until after U.S. ground forces withdrew from the 

theater. (For a discussion of those and other past military 

operations, see Appendix C.)

4. For much of the 2000s, the Army formally called some brigade 

combat teams “heavy BCTs,” but it has since renamed them 

“armored BCTs.”

5. That practice is most common for support units that perform 

logistics functions, such as transportation or maintenance. By 

contrast, units that support BCTs by providing artillery or aviation generally have a full set of subordinate units assigned to them.

Combat Units 194,000 133,000 328,000

Support Units 119,000 352,000 472,000

Overheada 138,000 44,000 183,000 ________ ________ ________

Total 452,000 530,000 982,000

Component Component Total

Active Reserve
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 21

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Army ground forces have had more difficulty, however, 

in achieving U.S. aims against adversaries who have 

employed unconventional methods of combat, such as 

guerrilla warfare. Notable examples of those difficulties 

include attempts to suppress Viet Cong and North 

Vietnamese army units during the Vietnam War, insurgents in Iraq, and the resurgent Taliban in Afghanistan. 

Because Army units generally performed well in direct 

combat, those adversaries often tried to avoid direct combat and achieve their objectives through other means. 

Unconventional operations can be extremely long, and 

U.S. adversaries frequently achieve their goals by surviving as a viable force until the United States leaves the 

theater.

The Army has periodically tried to change its structure 

in ways that would make it more successful at fighting 

unconventional conflicts. Historically, those attempts 

have often included efforts to increase the size and 

capability of special forces (units that specialize in 

unconventional missions such as guerrilla warfare and 

counterinsurgency). The Army’s special forces have tried to 

help U.S. allies train their own militaries to a higher level 

of capability or conduct their own counterinsurgency 

campaigns. Although special forces have had some success 

in such efforts, the United States has a limited ability to 

influence the governments of its allies. Moreover, as 

events in South Vietnam, Iraq, and Afghanistan demonstrate, some allies have difficulty defending themselves 

despite substantial long-term training and investment by 

the United States.

The future size and makeup of the Army will be affected 

by the types of conflicts and commitments that U.S. leaders expect to face as well as by the size of the defense budget. If the future security environment is dominated by 

scenarios that place more emphasis on naval and air 

forces—such as potential operations around Taiwan, the 

South China Sea, or the Strait of Hormuz at the mouth 

of the Persian Gulf—the need for Army ground forces 

may decline. (For a discussion of DoD’s planning scenarios for those and other areas, see Appendix C.) Conversely, the need for Army ground forces may increase if 

the United States has to contend with circumstances such 

as Russian aggression in Europe.

What This Chapter Covers

The rest of this chapter presents CBO’s analysis of the 

following major elements of the Army’s force structure 

(listed here with the percentage of the Department of the 

Army’s O&S costs that they account for):

B Armored brigade combat teams (24 percent); see 

page 22.

B Stryker brigade combat teams (17 percent); see page 28.

B Infantry brigade combat teams (40 percent); see 

page 32.

B Other units and activities, such as aviation brigades and 

special-operations forces (19 percent); see page 36.

This chapter also examines three topics of special concern 

to the Department of the Army:

B The integration of the Army’s active and reserve 

components; see page 38.

B The role of manning levels in units’ readiness for 

deployment; see page 40.

B Deployment times and rotation ratios; see page 42.
22 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Major Element of the Force Structure

Army Armored Brigade Combat Teams

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

Armored brigade combat teams (BCTs) are large tactical 

formations that operate fairly independently. They are 

designed to include about 4,700 personnel and are 

equipped with the heaviest and most powerful armored 

combat vehicles in the U.S. inventory: M1 Abrams series 

tanks, M2/M3 Bradley series infantry vehicles/scout vehicles, M109 series self-propelled howitzers, and numerous 

M2- and M113-derived support vehicles. (See Figure 2-1 

on page 24 and the legend in Figure 2-2 on page 26 for 

the size and organization of an armored BCT.) Vehicles 

such as those—which run on tracks for off-road mobility 

and are heavily armored to protect against attack—are 

not assigned to all elements of an armored BCT. Each 

BCT also has several hundred wheeled vehicles that generally are not armored. Nevertheless, armored BCTs are, 

by a large margin, the most heavily armed and armored 

variety of U.S. ground forces. 

Current and Planned Structure. The Army will field 

nine armored BCTs in its active component and five in 

the National Guard in 2017, with no plans to change 

those numbers through 2021. In all, the armored BCTs 

in the active and reserve components—along with their 

supporting units and overhead—account for about 

24 percent of the Army’s operation and support funding.

Purpose and Limitations. Armored BCTs are descendants of the heavy divisions that were intended, during 

the Cold War, to defend Europe in the event of a largescale attack by Soviet forces. Although in recent years the 

Army has not focused specifically on the ability to destroy 

opponents’ armored vehicles, armored BCTs still have 

strong antiarmor capability, particularly when supplemented with Army helicopters and other U.S. airpower. 

Armored BCTs can also be used against lighter conventional forces that do not include heavy armored vehicles. 

However, because armored BCTs are far superior to 

lighter forces in terms of firepower, protection, and 

cross-country mobility, few adversaries are likely to 

willingly commit their lighter forces in open combat 

against armored BCTs. (In ground combat, light forces 

tend to be less mobile than heavy forces because they 

are intended to fight on foot and because the wheeled 

vehicles that transport them to the battlefield have less 

off-road capability than tracked armored vehicles do.)

The main drawback of armored BCTs is that they lose 

many of their combat advantages in complex terrain 

(such as forests, jungles, mountains, or urban areas) as 

well as in unconventional combat (such as guerrilla warfare). In such conditions, armored vehicles are more vulnerable to attack, have less ability to use their firepower, 

and cannot benefit from their tactical mobility. Although 

armored BCTs still have some advantages over lighter 

forces under those conditions, defense planners generally 

believe that the high costs of armored BCTs relative to 

those of lighter forces make them less well suited for such 

missions. In addition, in areas with poor infrastructure, 

armored BCTs may be less suitable for some operations 

because of their logistics demands (such as high fuel consumption) and related issues (such as the need for bridges 

that can support the weight of armored vehicles).

Military Personnel per Unit 17,450 4,200 9,090 4,160

Annual Cost per Unit 2,610 500 840 1,280

(Millions of 2017 dollars)

Military Personnel per Unit 14,440 4,140 9,090 1,210

Annual Cost per Unit 820 180 390 240

(Millions of 2017 dollars)

National Guard Armored Brigade Combat Team

Total Direct Indirect Overhead

Active-Component Armored Brigade Combat Team
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 23

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A frequent concern raised about armored BCTs is that 

their weight and extensive support requirements make 

them harder and slower to deploy to distant locations 

than light forces are. In many cases, however, that limitation does not significantly hinder an operation. One 

reason is that although an armored BCT has much 

heavier equipment than, for example, an infantry BCT, 

the United States rarely deploys a single brigade of any 

type on its own, using air transport, to an unexpected 

location with great haste. Rather, a brigade is deployed as 

part of a full “force package” that typically includes a 

large number of support units, which diminishes the difference in equipment weight between heavy and light 

forces. Moreover, a deployment could involve many BCTs, 

which would overwhelm air-transport capabilities and 

make sea transport mandatory, and it could involve a location (such as the Korean Peninsula or the Persian Gulf) 

where the United States has stockpiled prepositioned 

equipment on land or on board ships. 

In addition, in many conflicts—such as the removal of 

Iraqi forces from Kuwait in 1991 (Operation Desert 

Storm) and the invasion of Iraq in 2003 (Operation Iraqi 

Freedom)—the United States had a long time to deploy 

forces, reducing the importance of deployment speed. 

(For a description of those and other past military operations, see Appendix C.) To the extent that U.S. planners 

are concerned about deployment speed, investments in 

stocks of prepositioned equipment and additional cargo 

ships can greatly reduce deployment times in most scenarios, without requiring the military to forgo the combat capabilities of heavy forces.

Past and Planned Use. Armored BCTs evolved from 

Cold War–era armored divisions and mechanized infantry divisions, which were referred to as heavy divisions.6

Their equipment and organization have historically been 

oriented toward high-intensity combat with conventional 

armored opponents, as was envisioned during the Cold 

War, when U.S. heavy forces were prepared to defend 

West Germany against massive Soviet armored assaults. 

More recently, the United States relied extensively on 

heavy divisions during Operations Desert Storm and 

Iraqi Freedom, but it did not use any heavy forces in the 

invasion of Afghanistan in 2001 (Operation Enduring 

Freedom). In later counterinsurgency operations in Iraq 

and Afghanistan, that pattern was repeated: The United 

States employed large numbers of heavy BCTs in Iraq but 

none in Afghanistan. However, the heavy BCTs used in 

Iraq often operated in a modified configuration without 

their heavy vehicles, which made them better suited to 

counterinsurgency and urban operations—an example of 

the way the Army adapts its units to meet the needs of 

each operation.

In the 1990s, the Department of Defense’s post–Cold 

War planning focused on the ability to fight two theatersize wars at the same, or nearly the same, time (see 

Appendix C). DoD generally assumed that each of those 

wars would require the equivalent of about 11 heavy brigades. (At the time, the Army used divisions as its basic 

units; it assumed that three heavy divisions and two 

armored cavalry regiments would be necessary for the 

combat phase of each war.) Subsequent planning has 

been more flexible but envisions that a similar number of 

combat brigades would be needed for a major conflict. 

Thus, according to that standard, the Army’s planned 

2021 force of nine active-component armored BCTs and 

five National Guard armored BCTs would probably not 

be sufficient for such a two-war scenario. In practice, 

however, the United States currently has few, if any, 

potential opponents that can field enough modern 

armored forces to require the Army to use large numbers 

of armored BCTs against them in a conflict. In addition, 

the United States has other types of BCTs (Stryker and 

infantry) that would be capable of contributing in a conflict, although they do not have the same characteristics 

as an armored BCT.

6. The Army sees substantial advantages in using armored units 

together with mechanized infantry units (infantry that are 

equipped with infantry fighting vehicles rather than with tanks). 

Thus, it combines the two types of units at all but the very lowest 

command levels. For a long time, such combined units were 

referred to generically as heavy forces. The Army recently changed 

their name from “heavy BCTs” to “armored BCTs,” but those brigades have the same mixture of armored and mechanized infantry 

units as before.
24 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Figure 2-1.

Units, Equipment, and Personnel in an Army Armored Brigade Combat Team

Continued

Combined Arms Battalion 

HQ 

Company

HQ 

Company

Rifle 

Company

Armor 

Company

Armor 

Company

Rifle 

Company

Combined Arms Battalion 

HQ 

Company

Rifle 

Company

Armor 

Company

Armor 

Company

Rifle 

Company

Combined Arms Battalion 

HQ 

Company

Rifle 

Company

Armor 

Company

Armor 

Company

Rifle 

Company

Cavalry Squadron

HQ

Troop

Cavalry

Troop

Cavalry

Troop

Cavalry

Troop

Fires (Artillery) Battalion

HQ 

Battery

Howitzer

Battery

(155 SP)

Target

Acquisition 

Platoon

Fires

Battery

(155 SP)

Fires

Battery

(155 SP)

Brigade 

Headquarters
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 25

CBO

Figure 2-1. Continued

Units, Equipment, and Personnel in an Army Armored Brigade Combat Team

Source: Congressional Budget Office, using data from the Department of Defense.

For a key to the icons in this figure, see Figure 2-2.

Tactical 

Unmanned 

Air System

Platoon

Combat

Engineer 

Company

Combat

Engineer 

Company

Signal 

Company

Military 

Intelligence

Company

HQ 

Company

Brigade Engineer Battalion

Distribution Company

Brigade Support Battalion

Field 

Maintenance 

Company

Medical

Company

HQ 

Company

Forward Support 

Company 

(Combined Arms

Battalion) 

Forward Support 

Company 

(Brigade Engineer 

Battalion)

Forward Support 

Company 

(Fires Battalion) 

Forward Support 

Company 

(Cavalry Squadron)

Forward Support 

Company 

(Combined Arms

Battalion) 

Forward Support 

Company 

(Combined Arms

Battalion) 
26 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Figure 2-2.

Legend for Army Equipment and Personnel

Continued

Armored Vehicles

M1A2 Abrams Main Battle Tank

M109A6 Paladin 155 mm Howitzer

M992A2 Ammo Support Vehicle

M2/3 Bradley Fighting Vehicle/

M7 Bradley Fire Support Vehicle

M577A1 Command Post Carrier

M113A3 Armored Personnel Carrier/

M1064 120 mm Mortar Carrier

M113A3 Ambulance

M577A1 Medical Treatment Vehicle

M1117 Armored Security Vehicle

M88A1 Medium Recovery Vehicle/

M88A2 Improved Recovery Vehicle (Hercules)

XM1150 Assault Breacher Vehicle With Mine Plow

M9 Armored Combat Earth Mover (ACE)

M2/3 Bradley Engineer Vehicle With Trailer

M1126 Stryker Infantry Carrier

M1127 Stryker Reconnaissance Vehicle

M1128 Mobile Gun System

M1129 Stryker Mortar Carrier

M1130 Stryker Command Vehicle

M1131 Stryker Fire Support Vehicle

M1132 Stryker Engineer Support Vehicle

M1133 Stryker Medical Evacuation Vehicle

M1134 Stryker Antitank Guided Missile Vehicle

M1135 Stryker Nuclear Biological Chemical

Reconnaissance System

M104 Wolverine Heavy Assault Bridge

XM1150 Assault Breacher Vehicle With Blade
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 27

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Figure 2-2. Continued

Legend for Army Equipment and Personnel

Source: Congressional Budget Office.

M998/M1038 High Mobility Multipurpose

Wheeled Vehicle (HMMWV)

M1113 Expanded Capacity HMMWV With

Rigid Wall Shelter

M1114/1151A1 Uparmored HMMWV

M1097A2 Heavy Variant HMMWV With Shelter

M997 HMMWV Ambulance

Secure, Mobile, Antijam, Reliable 

Tactical-Terminal (SMART-T)

AN/TSQ-190 Trojan Spirit HMMWV/Trailer

Unmanned Air System Ground Control Station

AN/MLQ-40 Prophet Detecting System

Countermeasures

Light Trucks Medium Trucks

Personnel

Other

M198 Towed 155 mm Howitzer

M119A1/A2 Towed 105 mm Howitzer 

M1120 Heavy Expanded Mobility Tactical 

Truck Load Handling System and Trailer

Heavy Trucks

M1074/M1075 Heavy Cargo Truck 

Palletized Load System Transporter

M1078 Light Medium Tactical Vehicle

M1083 Medium Tactical Vehicle

M1083 Medium Tactical Vehicle With

M1095 Cargo Trailer

M1083 Medium Tactical Vehicle With

Kitchen or Tool Set Trailer

M1083 Medium Tactical Vehicle With

Water Tank Trailer

M1083 Medium Tactical Vehicle With

Generator or Welding Trailer

M1083 Medium Tactical Vehicle With

Power Plant Trailer

M1088 Medium Tactical Vehicle 

Tractor With M129A3 Semitrailer

M1089 Medium Tactical Wrecker

M1088 Medium Tactical Vehicle 

Tractor With M172A1 Lowbed Semitrailer

Shadow Launch/Recovery Trailer and

RQ-7 Shadow Tactical Unmanned 

Air System

All Terrain Lifter Articulated System

(Atlas) Forklift

Interim High Mobility Engineer Excavator

Deployable Light Engineer Tractor (Deuce)

Rough Terrain Forklift

Multipurpose Loader

Ten Personnel

One Person

M1074 Palletized Load Transport With

Forward Repair System

M984A1 Heavy Expanded Mobility

Tactical Truck Wrecker

M978 Heavy Expanded Mobility Tactical

Truck Fuel Tanker With Fuel Trailer

M916 Tractor Truck With M172A1 

Lowbed Semitrailer

M977/M985 Heavy Expanded Mobility

Tactical Cargo With Trailer

M1977 Common Bridge Transporter With

Rapidly Emplaced Bridge Systems
28 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Army Stryker Brigade Combat Teams

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

Like armored brigade combat teams (BCTs), Stryker 

BCTs are large tactical formations that can operate 

relatively independently. However, Stryker BCTs are 

designed to have about 200 fewer personnel than 

armored BCTs are designed to have (approximately 

4,500) and are equipped not with heavy, tracked armored 

vehicles but with medium-weight, wheeled armored vehicles of the Stryker family. (That general type of vehicle is 

sometimes called an armored personnel carrier.) Not all 

of the elements of a Stryker BCT are assigned Stryker 

vehicles; each BCT also has several hundred wheeled 

vehicles that generally are not armored. (See Figure 2-3 

on page 30 and the legend in Figure 2-2 on page 26 for 

the size and organization of a Stryker BCT.) Even so, 

Stryker BCTs provide the Army with more infantry in 

armored personnel carriers than any other type of brigade 

combat team.

Current and Planned Structure. The Army will field 

seven Stryker BCTs in the active component and two in 

the National Guard in 2017. In its 2017 budget request, 

it indicated no plans to change those numbers through 

2021. Those Stryker BCTs—along with their supporting 

units and overhead—account for about 17 percent of the 

Army’s operation and support (O&S) funding.

Purpose and Limitations. Stryker BCTs were created as 

part of a 1999 initiative to transform the Army into a 

more mobile and responsive force. The Stryker family of 

vehicles was intended to provide a medium-weight force 

that would be easier to deploy rapidly than heavy forces 

but that would have more combat power and ability to 

move around the battlefield than light forces. Plans at the 

time called for making Stryker vehicles small and light 

enough to fit on C-130 transport aircraft. However, combat experience in Iraq has led the Army to improve the 

armor of most of its vehicles, and Stryker vehicles have 

become much too heavy to be transported on C-130s.

Although the Stryker force was originally envisioned as 

capable of rapid deployment to conventional operations, 

it has proved helpful in fighting unconventional forces, 

such as those in Iraq and Afghanistan. Such operations 

require large numbers of infantry personnel and benefit 

when all of those personnel have access to armored transport vehicles—both traits that Stryker BCTs possess. 

Similarly, the infrastructure in Afghanistan is too poor for 

the tanks and fighting vehicles of armored BCTs to operate there, but the lighter-weight Stryker vehicles can 

operate in parts of that country.

The main limitation of Stryker BCTs is that they truly are 

middle-weight forces. They are not as light as infantry 

BCTs (described in the next section), which makes them 

difficult to deploy by air on short timelines. But they also 

are not as well armed and protected as armored BCTs, 

which means they would suffer in a confrontation with a 

modern conventional armored force. Those disadvantages 

might not be meaningful in the context of long-term 

operations against insurgents, but they could be significant 

in a future conflict against conventional forces. Furthermore, although they can cope with poor infrastructure 

Military Personnel per Unit 17,180 4,440 8,590 4,150

Annual Cost per Unit 2,560 500 790 1,280

(Millions of 2017 dollars)

Military Personnel per Unit 14,230 4,450 8,590 1,190

Annual Cost per Unit 800 190 370 240

(Millions of 2017 dollars)

Total Direct Overhead Indirect

Active-Component Stryker Brigade Combat Team

National Guard Stryker Brigade Combat Team
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 29

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better than armored BCTs can, Stryker BCTs still face 

some constraints when operating in areas with poor road 

networks, and they pose a fairly significant logistics burden.

For the past decade, the Army has been reducing the fraction of armored BCTs in its force in favor of Stryker and 

infantry BCTs. The Army has often cited the cost of 

maintaining heavy forces as one of the reasons for that 

shift. However, the analysis that the Congressional Budget Office conducted for this report indicates that there 

is virtually no difference in operation and support costs 

between armored and Stryker BCTs. (The costs of acquiring Stryker vehicles and heavy armored vehicles can differ, however.) Although Stryker BCTs do not have a 

major O&S cost advantage over armored BCTs, their 

operational advantages in counterinsurgencies and areas 

with poor infrastructure may provide a sufficient rationale for the Army’s shift.

Past and Planned Use. Stryker BCTs are a relatively new 

type of unit and have been employed in only two major 

operations: the occupations of Iraq and Afghanistan. 

The Marine Corps used wheeled Light Armored Vehicles 

(known as LAVs), which are similar to Stryker vehicles, 

in a brigade-size formation during the invasion of Iraq in 

2003, reportedly to good effect. And the Army has 

deployed Stryker brigades to Afghanistan, despite (or perhaps because of) the relatively poor infrastructure there. 

(For a discussion of those and other past military operations, see Appendix C.)

Stryker BCTs did not exist during most of the 1990s, 

when the Department of Defense’s post–Cold War planning called for being able to fight two wars simultaneously (or nearly simultaneously). The Army’s force of 

seven active-component Stryker BCTs and two National 

Guard Stryker BCTs appears likely to be capable of contributing in any conflict: DoD envisions few scenarios in 

which infrastructure constraints are worse than those in 

Afghanistan, and few, if any, potential U.S. opponents 

have enough armored forces to threaten the viability of 

the medium-weight Stryker BCTs (see Appendix C). 
30 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Figure 2-3.

Units, Equipment, and Personnel in an Army Stryker Brigade Combat Team

Continued

Cavalry Squadron

HQ 

Troop

Cavalry

Troop

Cavalry

Troop

Cavalry

Troop

HQ 

Battery

Fires 

Battery

(155 T)

Fires (Artillery) Battalion

Target

Acquisition

Platoon

Fires 

Battery

(155 T)

Fires 

Battery

(155 T)

Brigade 

Headquarters

HQ

Company

Infantry Battalion 

HQ Company

Rifle 

Company

Rifle 

Company

Rifle 

Company

Infantry Battalion 

HQ Company

Rifle 

Company

Rifle 

Company

Rifle 

Company

Infantry Battalion 

HQ Company

Rifle 

Company

Rifle 

Company

Rifle 

Company
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 31

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Figure 2-3. Continued

Units, Equipment, and Personnel in an Army Stryker Brigade Combat Team

Source: Congressional Budget Office, using data from the Department of Defense.

For a key to the icons in this figure, see Figure 2-2 on page 26.

Brigade Support Battalion

Distribution Company

ASLMS ASLMS 

ASLMS ASLMS 

ASLMS ASLMS 

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

Field Maintenance Company

Forward 

Support Company

(Brigade Engineer

Battalion)

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

HQ 

Company

Medical

Company

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

Forward 

Support Company 

(Cavalry Squadron)

Forward 

Support Company 

(Infantry Battalion)

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

Forward 

Support Company 

(Fires Battalion)

Forward 

Support Company 

(Infantry Battalion)

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

Forward 

Support Company 

(Infantry Battalion)

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

FLAMMABLE 

NO SMOKING WITHIN 50 FEET

Brigade Engineer Battalion

Signal 

Company

Military 

Intelligence

Company

Tactical 

Unmanned

 Air System

Platoon

Antiarmor

Company

HQ

Company

Combat Engineer

Company

Combat Engineer

Company
32 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Army Infantry Brigade Combat Teams

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

Infantry brigade combat teams (BCTs)—also commonly 

called light BCTs—are relatively independent tactical 

formations that are designed to include approximately 

4,400 personnel.7

 Most of those personnel are expected to 

engage in combat on foot, although each infantry BCT 

also has several hundred wheeled, generally unarmored, 

vehicles assigned to it for transport. (See Figure 2-4 on 

page 34 and the legend in Figure 2-2 on page 26 for the 

size and organization of an infantry BCT.) Unlike 

armored or Stryker BCTs, infantry BCTs come in some 

specialized variants. For example, airborne units (such as 

the brigades of the 82nd Airborne Division) are specially 

trained and equipped to drop by parachute from fixedwing aircraft, and air-assault units (such as the brigades of 

the 101st Air Assault Division) are given special training 

and additional supporting helicopters to conduct assaults 

from rotary-wing aircraft. Because they have the least 

equipment weight, infantry BCTs are considered the 

easiest to deploy of all types of brigade combat teams.

Current and Planned Structure. Infantry brigade combat teams are the most numerous type of BCT. The Army 

will field 14 in its active component and 19 in the 

National Guard in 2017, with no plans to change those 

numbers through 2021. Together, infantry BCTs and 

their supporting units and overhead are responsible for 

about 40 percent of the Army’s operation and support 

funding.

Purpose and Limitations. Infantry BCTs are a product 

of the Army’s renewed focus in the 1980s on the concept 

of light infantry, in which troops fight entirely on foot, 

although with some motor transport available. Such 

forces are designed to be capable of deploying rapidly 

to distant locations. However, because they have no 

armored vehicles and few vehicle-mounted weapons, the 

Army’s light forces lack the protection and combat power 

of heavy forces. Nevertheless, infantry BCTs have significant firepower, and they are capable of calling on the 

same array of support assets—such as artillery, attack 

helicopters, and air strikes—as any other type of BCT. 

In addition, infantry BCTs can often operate more effectively than armored forces in such difficult locations as 

cities, forests, or mountains, where they can derive substantial defensive benefits from the terrain. For those reasons, unless infantry BCTs are facing large armored forces 

in unfavorable terrain, they are considered suitable for a 

wide variety of operations.

The Army’s different types of light forces are often 

grouped together in discussions of their utility in conflicts, but the specialized abilities of airborne and airassault units are intended to provide important and 

unique capabilities. For example, both types of forces 

contribute to the Army’s ability to conduct forcible-entry 

operations, which involve gaining access to enemy 

Military Personnel per Unit 16,250 4,230 8,090 3,920

Annual Cost per Unit 2,410 450 750 1,210

(Millions of 2017 dollars)

Military Personnel per Unit 12,720 3,560 8,090 1,060

Annual Cost per Unit 700 140 350 220

(Millions of 2017 dollars)

Total Direct Overhead Indirect

Active-Component Infantry Brigade Combat Team

National Guard Infantry Brigade Combat Team

7. In the table above, the number of direct personnel is much smaller 

for a National Guard infantry BCT than for an active-component 

infantry BCT because the Guard BCTs are still making the transition from a structure that includes two infantry battalions to a 

structure that includes three infantry battalions.
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 33

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territory that cannot be reached from adjacent land areas. 

(The capability for such operations is discussed in a 

special-topic entry on forcible-entry capability on 

page 72.)

Although infantry BCTs are touted for their ability 

to deploy quickly, that characteristic may be less 

advantageous than it would seem at first glance. With 

support units excluded, an infantry BCT has roughly 

one-quarter of the unit weight of an armored BCT, and 

all of its equipment can be transported by air. However, 

for a variety of reasons, that difference is likely to be valuable only in certain types of small operations. Support 

units for heavy and light forces are fairly similar in 

weight; though tanks require more logistical support 

than people do, the hundreds of wheeled vehicles in both 

armored and infantry BCTs require similar logistical support (compare Figure 2-1 on page 24 and Figure 2-4 on 

page 34). Moreover, unless infantry BCTs are deployed 

without support (which is unlikely except for very short 

and low-risk missions), the need to deploy support units 

as well as combat units makes fully supported infantry 

BCTs only a little faster to deploy than heavier BCTs—

and means that both types of units would probably 

require sea transport for any large operation. The Army 

is most likely to benefit from the light weight of infantry 

BCTs when deployment speed is more important than 

combat power (such as in some humanitarian interventions) or when the total force to be committed is fairly 

small (such as in the initial phase of the invasion of 

Afghanistan).

Past and Planned Use. Infantry BCTs evolved from the 

Army’s various infantry, airborne, and air-assault divisions, all of which had substantial similarities in organization and equipment. After focusing for many years on 

trying to fully mechanize all nonairborne infantry units, 

the Army revived the light-infantry concept in the 1980s. 

Light units were seen as a cost-effective way to increase 

the size of U.S. ground forces, especially for scenarios 

other than defending against Soviet armored assaults.

In recent decades, the operation to remove Iraqi forces 

from Kuwait in 1991 and the invasion of Iraq in 2003 

involved light forces (at the time, infantry divisions rather 

than BCTs) to only a limited extent. By contrast, the 

invasion of Afghanistan in 2001 depended entirely on light 

forces, including Marine Corps and special-forces units. 

That pattern recurred in subsequent counterinsurgency 

operations in Iraq and Afghanistan: The United States 

used limited numbers of infantry BCTs in Iraq but relied 

heavily on them in Afghanistan (for a discussion of those 

and other past military operations, see Appendix C). 

However, in those operations, infantry units were 

assigned more vehicles than usual for mobility, and they 

were given armored vehicles for protection against improvised explosive devices as the use of those devices became 

more common.

In the 1990s, the Department of Defense’s post–Cold 

War planning focused on the ability to fight two theatersize wars at the same, or nearly the same, time (see 

Appendix C). DoD generally assumed that each of those 

wars would require the equivalent of about six light brigades. (At the time, the Army used divisions as its basic 

units; it assumed that two light divisions would be necessary for the combat phase of each war.) Subsequent planning has been more flexible but envisions that a similar 

number of combat brigades would be needed for a major 

conflict. Thus, according to that standard, the Army’s 

planned 2021 force of 14 active-component infantry 

BCTs and 19 National Guard infantry BCTs would probably be more than sufficient for a two-war scenario (see 

Appendix C). The United States currently has few, if any, 

potential opponents that can field large enough armored 

forces to make the use of infantry BCTs infeasible.
34 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Figure 2-4.

Units, Equipment, and Personnel in an Army Infantry Brigade Combat Team

Continued

Infantry Battalion 

HQ 

Company

HQ 

Company

Weapons

Company

Rifle 

Company

Rifle 

Company

Rifle 

Company

Infantry Battalion 

HQ 

Company

Weapons

Company

Rifle 

Company

Rifle 

Company

Rifle 

Company

Infantry Battalion 

HQ 

Company

Weapons

Company

Rifle 

Company

Rifle 

Company

Rifle 

Company

Fires (Artillery) Battalion

HQ 

Battery

Fires Battery

(105 T)

Fires Battery

(155 T)

Fires Battery

(105 T)

Target

Acquisition

Platoon

Cavalry Squadron

HQ Troop Motorized

Cavalry 

Troop

Dismounted

Cavalry

Troop

Motorized

Cavalry 

Troop

Brigade 

Headquarters
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 35

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Figure 2-4. Continued

Units, Equipment, and Personnel in an Army Infantry Brigade Combat Team

Source: Congressional Budget Office, using data from the Department of Defense.

For a key to the icons in this figure, see Figure 2-2 on page 26.

Tactical 

Unmanned 

Air System

Platoon

HQ Company

Combat Engineer 

Company

Combat Engineer 

Company

Signal 

Company

Military 

Intelligence 

Company

Brigade Support Battalion Brigade Engineer Battalion

HQ Company

MTRCS

Distribution Company Field 

Maintenance 

Company

Medical

Company

Forward Support Company (Brigade Engineer Battalion)

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

Forward Support 

Company

(Cavalry Squadron) 

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

MTRCS

Forward Support 

Company

(Infantry Battalion)

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

MTRCS

Forward Support

Company

(Fires Battalion)

MTRCS

Forward Support 

Company

(Infantry Battalion)

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

MTRCS

Forward Support 

Company

(Infantry Battalion)

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

NO SMOKING WITHIN 50 FEET

MTRCS
36 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Other Department of the Army Units and Activities

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. In the analytic framework used for this report, other units and activities are generally considered to not have any units supporting them and thus to not 

have any indirect personnel or costs.

Although the vast majority of Army units are connected 

with brigade combat teams (BCTs), the service has a 

small number of other units that are not directly linked 

to BCTs, such as helicopter units and various specialoperations forces. Together, those units, along with their 

associated overhead, account for 19 percent of the Army’s 

operation and support funding.

Through World War II, the Army used various types of 

fixed-wing combat aircraft. After the war, however, the 

Air Force was spun off as a separate service from the 

Army. Since then, interservice agreements have prohibited the Army from using fixed-wing aircraft for combat 

(although it continues to use them for other purposes, 

such as reconnaissance and transport). Instead, the 

Army’s aviation brigades rely on helicopters.

In most respects, aviation brigades are similar to other 

types of supporting forces (as defined in this analysis), 

but they merit separate treatment because of their visibility and cost, the Army’s occasional use of them as independent forces, and the ease of distinguishing them from 

other supporting forces. The Army will field 11 aviation 

brigades in its active component in 2017 but plans to 

reduce that number to 10 by 2019. It will also field 

11 aviation brigades in the reserve component but 

plans to increase that number to 12 by 2018. 

The Army’s aviation brigades provide important forms of 

support in almost all operations involving Army forces. 

Those brigades include attack helicopters (AH-64 

Apaches to attack targets on the ground) and utility and 

cargo helicopters (UH-60 Blackhawks and CH-47 

Chinooks to transport soldiers, equipment, and supplies). 

Until recently, the Army also fielded reconnaissance helicopters (OH-58 Kiowas to scout for enemy forces), but it 

has since retired them. For light-infantry forces operating 

in poor terrain with limited infrastructure—such as 

Military Personnel per Unit 4,300 3,020 0 1,280

Annual Cost per Unit 890 490 0 410

(Millions of 2017 dollars)

Military Personnel per Unit 2,750 2,520 0 230

Annual Cost per Unit 200 160 0 50

(Millions of 2017 dollars)

Total Military Personnel 45,100 32,370 0 12,730

Total Annual Cost 7,210 3,190 0 4,020

(Millions of 2017 dollars)

Total Military Personnel 12,570 8,860 0 3,710

Total Annual Cost 3,180 2,000 0 1,180

(Millions of 2017 dollars)

Total Direct Overhead Indirecta

Active-Component Aviation Brigade

Reserve-Component Aviation Brigade

Army Special-Operations Forces

Rest of the Army
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 37

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portions of Afghanistan—helicopter transportation is 

often the only practical method of deploying troops to 

and from combat operations. 

The role of the Army’s attack helicopters (and, to a lesser 

degree, its former reconnaissance helicopters) has been 

the subject of debate, however. Those aircraft had a 

mixed record in some combat operations, such as in 

Kosovo in 1999 and in the initial phases of Operation 

Iraqi Freedom in 2003. Some observers argue that the 

Army’s attack helicopters are a relatively wasteful and 

duplicative means of providing close air support (attacks 

by aircraft on hostile targets that are close to friendly 

ground or naval forces). In that view, close air support is 

better provided by more capable fixed-wing aircraft from 

the other services. Other observers maintain that 

unmanned aerial vehicles (discussed in Chapter 4 in an 

entry “Air Force Unmanned Air System Squadrons,” on 

page 100) are well suited to take over the roles traditionally performed by attack and reconnaissance helicopters. 

Still other observers argue that the Army’s attack helicopters have a number of unique advantages—such as the 

ability to fly at low speeds—that are useful for working 

closely with ground forces. Adding fuel to the debate is 

the fact that the Army has had difficulty developing new 

reconnaissance helicopters; it canceled two attempts to 

develop a replacement for the former Kiowa fleet.(Army 

officials maintain that they continue to need reconnaissance helicopters, but they currently have no active program to purchase a replacement.)

Aviation brigades are one of the most costly types of 

supporting forces in the Army, and helicopters are some 

of the most expensive weapon systems that the Army 

procures. Thus, any future developments that reduced 

the Army’s use of attack and reconnaissance helicopters 

could yield substantial savings.

The Army’s special-operations forces include the 75th 

Ranger Regiment, the 160th Special Operations Aviation 

Regiment, and seven special-forces groups. (The costs 

and personnel numbers shown in the table above are for 

the Army’s special-operations forces as a whole rather 

than for individual units.) Those units—along with the 

special-operations forces of the other military services—

are trained, equipped, and overseen by the Department of 

Defense’s Special Operations Command (SOCOM). 

They focus on such missions as unconventional warfare, 

special reconnaissance, counterterrorism, or the training 

of foreign militaries. The forces overseen by SOCOM are 

discussed in more detail in Chapter 5, which deals with 

defensewide activities in an entry, “Special Operations,” 

on page 111. 

By the Congressional Budget Office’s estimate, more than 

12,000 military personnel and almost $3.2 billion a year 

are devoted to units and activities of the Army other 

than those described in this chapter. They include a 

variety of smaller organizations providing niche capabilities that are neither BCTs nor units organized to support 

BCTs. The largest example is the Army’s operation of the 

Ground-Based Midcourse Defense portion of the 

national missile defense system. That system is the subject of a special-topic entry in Chapter 5, “Missile 

Defense,” on page 120. Other examples include the 

Army’s contributions to various joint commands and 

defensewide organizations, as well as some miscellaneous 

command-and-control functions.
38 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Special Topic

Integration of the Army’s Active and Reserve Components

Each U.S. military service has an active and a reserve 

component, but the nature and size of the Army’s reserve 

component—as well as the way in which the Army integrates its two components—make the relationship 

among the active Army, the Army Reserve, and the Army 

National Guard a topic of special interest. Roughly twothirds of the reserve-component personnel in the U.S. 

military are in the Army. Thus, in most cases, the Army’s 

policies toward its reserve component have a greater effect 

on how heavily the Department of Defense employs 

reserve personnel than do the policies of any other 

service.

In a traditional reserve system, reserve units represent 

additional increments of force that can be used if forces in 

the active component prove insufficient—as was the case 

in the Army in earlier decades and as is still largely the 

case in the Marine Corps. However, since the end of the 

Vietnam War, the Army has structured itself in a way that 

concentrates its combat forces in the active component 

and concentrates the units that provide essential support 

for those combat forces in the reserve component. (The 

active component contains only 46 percent of the Army’s 

total military personnel but 59 percent of the personnel 

in combat units; likewise, the reserve component contains 54 percent of the Army’s military personnel but 

75 percent of the personnel in support units.) 

That structure requires the Army to commit support 

units from the reserve component in order to deploy even 

modest numbers of combat units from the active component.8

 The need for reserve-component units to support 

active-component combat forces was the main reason 

that the Army activated large numbers of reservists during the occupation of Iraq, for example. (Combat units in 

the reserve component were also activated and deployed 

for the occupation, but in much smaller numbers than 

active-component combat units.) Another result of that 

heavy reliance on reserve support personnel is that the 

Army can maintain a much larger number of combat 

units in its active component, at lower cost, than it could 

if it were organized in a less integrated way. 

The benefits and drawbacks of the Army’s integrated 

structure have been the subject of numerous public 

debates and several Congressionally mandated commissions. Many of those debates have focused on intangible 

effects of that structure on reserve-component personnel 

or on the decisions of policymakers. However, some 

effects of that structure can be quantified.

If the Army stayed the same size but ceased having 

specialized active and reserve components and instead 

adopted a policy of supporting active-component combat 

units with active-component support units (and supporting reserve-component combat units with reservecomponent support units), the active component would 

be able to support about 21 brigade combat teams 

(BCTs) rather than the current 30 BCTs. At the same 

time, the Army would be able to sustain 37 BCTs in the 

reserve component rather than the current 26. 

If, instead of remaining the same size, the Army wanted 

to fully support its current 30 active-component BCTs 

with active-component support units rather than reservecomponent support units, it would need to add at least 

148,000 support personnel to the active component. And 

if the additional personnel had costs similar to those of 

current active-component Army personnel, the Department of Defense would require an additional $20 billion 

a year in operation and support funding.

The Army does not appear to be considering any dramatic changes to its current policies for integrating the 

active and reserve components (although smaller changes 

are frequently under consideration). However, the above 

examples show that any proposal to eliminate the active 

component’s dependence on reserve-component support 

units would entail trade-offs—either by requiring a much 

larger active-component force or by requiring the Army 

to shift combat units from the active component to the 

reserve component.

8. The ratio of active- to reserve-component personnel varies for 

each type of support unit. For example, the Army has a fairly large 

complement of aviation brigades in the active component, so it 

does not necessarily have to activate reserve-component aviation 

brigades for smaller deployments. At the other end of the spectrum, support units that focus on civil affairs or psychological 

operations have historically been overwhelmingly concentrated in 

the reserve component (with few, if any, units in the active component), so the Army must activate reservists for any operation 

requiring such units.
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The Marine Corps and the Navy seem unlikely, in the 

foreseeable future, to adopt a model similar to the Army’s 

integration of its active and reserve components. The 

Marine Corps’ combat units deploy more frequently and 

routinely during peacetime than the Army’s combat units 

do. That deployment schedule would make the Army’s 

integrated model difficult for the Marine Corps to adopt 

unless DoD was willing to require frequent and routine 

peacetime mobilizations of reserve support units. The 

Navy is generally more constrained by the number of 

ships in its inventory than by the number of personnel 

it has. (The Air Force already uses a model in which its 

active and reserve components are even more deeply integrated and interdependent, in some respects, than the 

Army’s are, as discussed in more detail in a section in 

Chapter 4, “Distribution of Air Force Personnel,” on 

page 82.)
40 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Special Topic

Manning Levels, Readiness, and Deployability of Units

Discussions of the size of the force structure, costs per 

unit, or the readiness of units for deployment are complicated by the fact that many units do not operate with the 

number of military personnel officially required to fill 

them.9

 Conceptually, all units in the U.S. military have 

a required number of personnel, and each service has a 

given force structure, which means that each service 

should theoretically have a set number of personnel it 

needs for its units. However, for various reasons, the 

Department of Defense frequently operates units with 

more or fewer personnel than they are designed for—a 

practice known as overmanning or undermanning. 

Manning levels affect the number of units that a service 

can field from its total personnel, as well as the readiness 

and deployability of those units, especially in the Army 

and Marine Corps.10 Thus, decisions about manning 

levels are closely tied to the cost and utility of any given 

force structure. Such decisions also mean that the number 

of personnel included in a given force structure could 

vary widely, so there is no single correct number for how 

many people a service theoretically requires.

In this report, estimates of funding and personnel per 

unit are based on the actual manning levels that DoD has 

planned for the future. In most cases, changes to DoD’s 

decisions about manning levels would alter units’ costs, 

generally in almost linear fashion: A force consisting of 

units with lower manning levels than required would cost 

less (and need fewer personnel) but would be less ready 

and deployable; the opposite would be true for a force 

consisting of units with higher manning levels than 

required.

Reasons for Overmanning or Undermanning Units.

Assigning more people to a unit than required can be useful for a number of reasons. The most important is that 

when a unit is deployed, some fraction of its personnel 

will be unable to accompany the unit because of such 

issues as medical problems or impending separation 

from military service. If the unit is exactly at its required 

personnel level, the absence of those nondeployable personnel will leave the unit below full strength for its 

deployment. Overmanning nondeployed units provides a 

cushion of extra personnel, increasing the likelihood that 

they will be able to deploy with their full complement of 

required personnel. Experience suggests that units need a 

cushion of at least 10 percent of their required personnel 

in order to be realistically expected to deploy at full 

strength.

At some level, further overmanning would probably have 

diminishing returns, such that a force structure would be 

unlikely to benefit significantly from more personnel. In 

practice, however, the Army and Marine Corps do not 

appear to have neared that level at any point in recent 

years.

Undermanning units has its own advantages: reducing the 

cost of maintaining a given set of units or allowing a service 

to maintain more units with a given number of personnel 

than it could otherwise. However, undermanning makes it 

harder for a service to deploy combat units with their full 

complement of personnel. One possible use of undermanning that can avoid that problem involves what are 

known as cadre units. Such units are maintained with a 

small number of highly trained and experienced personnel but few junior personnel; when the need arises to 

expand the force, junior personnel can be added to the 

unit fairly rapidly (for instance, through a draft). That 

practice allows a service to increase its number of units 

much faster than it could if it created units from scratch. 

The Soviet Union used cadre units frequently, but the 

United States has historically preferred to have smaller 

numbers of readier units.

In the U.S. military, when undermanned units are 

required to deploy, they generally receive an infusion of 

personnel from other units to bring them up to their 

required numbers. Those transfers, referred to as 

9. Units generally have a “required” number of personnel (the number of people that the unit is theoretically designed for) and an 

“authorized” number of personnel (the number of people that the 

service has funded). The difference between those two numbers is 

usually small and fairly technical, so for this analysis, the Congressional Budget Office chose to focus on authorized numbers. With 

units that are not subject to deployment—primarily administrative organizations—personnel requirements are essentially 

dictated by the units’ expected workloads.

10. Decisions about manning levels are less significant for the Navy 

and Air Force because the number of units they can field depends 

to a greater extent on the number of ships and aircraft they are 

able to purchase.
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cross-leveling, alleviate the short-term problem of an 

individual unit’s being below required strength. But 

because the additional personnel must come from other 

units, cross-leveling is likely to leave nondeployed units 

even more short of personnel, causing a cascade of personnel shortages when the “donor” units in turn are 

required to deploy. (Integrating the transferred personnel 

into a new unit can also cause problems with that unit’s 

cohesion and readiness.) For example, during the late 

1990s and early 2000s, combat brigades in the Army 

National Guard were often kept at only 80 percent to 

90 percent of their required strength. Cross-leveling led 

to exactly that problem when the Army began deploying 

large numbers of National Guard brigades to Iraq in 

2005.

Effects of Manning Levels on Readiness and 

Deployability. Most units in the U.S. military receive 

periodic ratings of their readiness for deployment. Under 

DoD’s assessment system, those ratings are based partly 

on the percentages of required personnel and equipment 

a unit has and on the training the unit has completed. 

Unit commanders have some leeway to adjust the ratings 

if they consider it necessary. Barring such adjustments, a 

unit must have a manning level of more than 90 percent 

to be considered fully ready for combat, and the more 

undermanned the unit is, the further it is considered 

from being ready.

Manning levels have a more direct connection with unit 

readiness than do other relevant factors, such as funding.11 Any given force structure requires a specific number of personnel to allow each unit to achieve a manning 

level of more than 90 percent. If the number of personnel 

available to the force is smaller than that specific number, 

some units will fall below the 90 percent threshold and be 

considered less than fully ready. DoD and the individual 

services commonly give higher priority to some units, 

manning them at higher levels than a service’s average and 

leaving other units at below-average levels. Such decisions 

change the distribution of personnel, but they do not 

change the average manning level overall.

A related characteristic used to describe units is deployability. Unlike a readiness rating, deployability is not a 

formal measure; rather, it refers to the real-world ease of 

actually deploying a unit to military operations. In general, a unit must be kept at more than 100 percent of its 

required manning level to be deployable, unless it receives 

an infusion of additional personnel.

Because the services have an incentive to overman units 

that are likely to be deployed, even a force that notionally 

has enough personnel to man all units at 100 percent 

may choose to overman deployable units and underman 

nondeployable ones (such as administrative organizations). The Army engaged in that practice during the 

2000s, for example. Personnel are costly, so allocating 

them as scarce resources toward higher-priority uses and 

away from lower-priority uses can be a reasonable way 

to maximize the combat potential of a limited pool of 

people. However, such considerations mean that the readiness or manning of any given unit is not a reliable indicator of the readiness or manning of the whole force. 

A unit’s manning level may reflect the priority a service 

assigns to that unit more than it reflects the manning 

level of the service as a whole.

11. For a discussion of the relationship between readiness and funding, see Congressional Budget Office, Linking the Readiness of the 

Armed Forces to DoD’s Operation and Maintenance Spending

(attachment to a letter to the Honorable C.W. Bill Young, 

April 25, 2011), www.cbo.gov/publication/22105.
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Special Topic

Deployment Times and Rotation Ratios

When making plans for units, the Department of 

Defense distinguishes between a unit at its home station 

(typically, its permanent base) and a unit deployed away 

from that station. Units can be deployed away from home 

for numerous reasons, such as training exercises. But the 

most significant types of deployment are those required 

to sustain U.S. forces overseas—either for military operations, such as the occupations of Iraq and Afghanistan, or 

for routine military presence in various parts of the 

world. The Navy and Marine Corps have a long-standing 

tradition of conducting routine peacetime deployments 

to provide presence overseas, whereas the Army and Air 

Force have not traditionally deployed units overseas during peacetime. (Military personnel stationed at some 

overseas bases, such as in Germany or Japan, are 

considered to be at their home station rather than 

on deployment.) 

An important factor about current deployments is that 

DoD does not keep units away from their home station 

indefinitely. Instead, units return home periodically to 

limit the stress of deployments on personnel and their 

families, to repair and replace their equipment, to engage 

in training exercises, and so forth. Because of that policy, 

any long military operation or continuing overseas presence requires DoD to have other units available that it 

can deploy to replace returning units—a practice known 

as unit rotation. By contrast, in earlier conflicts, such as 

in Korea and Vietnam, the United States pursued a policy 

of individual rotation, in which ground and air units 

remained overseas indefinitely and individual personnel 

were cycled through them. DoD changed that practice 

because individual rotation was thought to lead to poor 

unit cohesion. With unit rotation, the need to alternate 

units between their home station and deployment means 

that the military’s forces can be thought of as a pool of 

units, divided into deployed and nondeployed subsets. 

Each military service has its own policies governing how 

long its units can be deployed and how long they should 

remain at their home station. Such policies result in a theoretical maximum number of units that can be sustained 

on extended deployments at any point in time while 

adhering to a service’s policies. For example, the Army’s 

official policy for most of the past decade has been for 

units in the active component to be deployed for up to 

one year and then spend at least two years at their home 

station between deployments. (The Army was not able to 

meet those goals during the occupation of Iraq.)12 That 

policy implies that the Army can sustainably deploy onethird of its active-component force to extended operations overseas while the other two-thirds is at home—for 

a rotation ratio of home-station units to deployed units of 

2 to 1.13 Deploying a unit over several rotation cycles 

through a theater in excess of that rotation ratio is generally considered unsustainable, in part because it affects 

the desire of the unit’s members to stay in the military.

Because of differences between types of units and the policies of the individual services, there is no single rotation 

ratio for all military forces. In general, the services expect 

units in the active component to be able to sustain more 

deployments than units in the reserve component. (In 

many cases, DoD prefers to minimize reserve-component 

deployments, if possible.)

When necessary, DoD can deploy more forces than suggested by rotation ratios, as it did for extended periods 

during the occupation of Iraq. Moreover, rotation ratios 

are the result of policy decisions and can be changed. 

Thus, in times of great military need, nothing prevents 

DoD from deploying as many units as are available for as 

long as necessary, as it did during World War II. However, the performance of units generally degrades over 

time when they are deployed, so such a decision can have 

drawbacks, which worsen as time goes on. But in an 

operation expected to be of limited duration (such as 

Operation Desert Storm in 1991), DoD can realistically 

deploy far more units than the sustainable level because it 

does not have to plan on sustaining the force involved in 

the operation indefinitely.

Given the need to have several units in the force to sustain a single deployed unit, if DoD has plans to keep large 

12. The Army had a different standard for deploying reservecomponent forces, which it also had trouble adhering to in Iraq.

13. Previously, DoD defined a rotation ratio as the ratio of the total 

number of units in the force to the number of units deployed. 

Thus, in the Army example, what is currently called a 2:1 ratio 

(two-thirds of the force at home station and one-third deployed) 

was previously called a 3:1 ratio (for every three units in the force, 

one was deployed). 
CHAPTER 2: DEPARTMENT OF THE ARMY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 43

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numbers of forces deployed overseas, those plans will 

generally require larger forces than plans that only anticipate operations of a limited duration. For example, the 

Army grew to 45 active-component brigade combat 

teams (BCTs) and 28 National Guard BCTs in the midto late 2000s in order to sustain 20 deployed BCTs. (The 

45 active-component BCTs provided 15 of the 20 deployed 

BCTs, and the 28 National Guard BCTs provided the 

other 5.) Currently, however, the need to sustain forces 

deployed overseas is not part of the Army’s planning strategy, which has allowed the service to shrink to a force of 

30 active-component BCTs and 26 National Guard 

BCTs (which would be sufficient to sustain about 

15 deployed BCTs).

CBO

CHAPTER

3

Department of the Navy

Overview

The Department of the Navy (DoN) includes the active 

components of the Navy and Marine Corps, the Navy 

Reserve, the Marine Corps Reserve, and all federal civilians employed by the Navy or Marine Corps. It is the 

second-largest military department by number of military 

personnel and has the second-largest operation and support (O&S) budget. Because of its sizable acquisition 

funding, however, it has a larger total budget than any 

other military department.

The integration of the Navy and Marine Corps in a single 

department reflects the historical relationship between 

those two services. Marines originated as sea-based soldiers, who were transported on naval vessels, engaged in 

hand-to-hand combat during sea battles, and provided 

armed landing parties for operations on shore (as well as 

deterring mutinies). Although marines no longer routinely provide detachments for U.S. Navy surface combatants, the Marine Corps still defines itself in part as 

“soldiers of the sea, providing forces and detachments to 

naval ships and shore operations.”1

 Unlike the other military departments, which are responsible for a single service, the Department of the Navy oversees the budgets of 

both the Navy and Marine Corps, and the two services 

are tightly integrated in a way that the other armed services are not. (That integration is discussed in detail in a 

special-topic entry on page 70.)

The Navy is the branch of the military responsible for 

providing all of the United States’ naval power and a 

significant portion of its airpower. The largest and 

most powerful conventional unit in the Navy is a 

carrier strike group (CSG), formerly called a carrier 

battle group. A CSG consists of an aircraft carrier, its 

associated aircraft (known as a carrier air wing), and a 

group of accompanying ships. The Navy’s long-term 

plans call for maintaining 11 carrier strike groups over 

much of the next 30 years.2

In addition to aircraft carriers, the Navy has about 

100 surface combatants (see Table 3-1), which consist, 

in roughly decreasing order of size, of cruisers, destroyers, 

frigates, and littoral combat ships. The Navy also includes 

10 amphibious ready groups (ARGs)—sets of three 

amphibious ships that transport Marine Corps ground 

and air units when they are deployed. Finally, the Navy 

maintains a fleet of submarines, including more than 

50 attack submarines, which are responsible for attacking 

enemy surface ships and submarines, and 14 ballistic 

missile submarines, which are responsible for providing 

about two-thirds of the United States’ nuclear deterrent 

(as measured by the number of nuclear weapons they 

carry).

The Marine Corps is a hybrid service, with units that 

engage in combat on the ground and in the air. The 

Marine Corps organizes its forces into task forces, each 

with a command, ground combat, air combat, and support element. The largest such task force, a Marine expeditionary force (MEF), includes a ground combat division, an air wing, and a support group. The active 

component of the Marine Corps has three MEFs, 

including a total of three divisions, three air wings, 

and three logistics groups. The Marine Corps Reserve 

contains one division, one air wing, and one support 

group, although they are not organized into a fourth

1. U.S. Marine Corps, “History & Heritage—Our Purpose” (2015), 

www.marines.com/history-heritage/our-purpose. 

2. At present, because of the planned gap between the retirement of 

one carrier and the commissioning of another, the Navy has only 

10 carriers. For a detailed discussion of the Navy’s shipbuilding 

plans, see Congressional Budget Office, An Analysis of the 

Navy’s Fiscal Year 2016 Shipbuilding Plan (October 2015), 

www.cbo.gov/publication/50926. In addition, although the 

Navy’s plans call for maintaining 11 carrier strike groups, the 

service fields only 10 carrier air wings because the air wings rotate 

among carriers, and at any given time at least one carrier is undergoing an extended overhaul (and thus, does not need an air wing).
46 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Table 3-1.

Number of Major Combat Units in the Navy and 

Marine Corps, 2017 and 2021

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

Marine expeditionary force. The MEFs, divisions, air 

wings, and logistics groups are not standardized units but 

instead vary in size and composition. For that reason, the 

Congressional Budget Office has based its analysis of 

the force structure of the Marine Corps on smaller, more 

standardized units: Marine infantry battalions and aircraft 

squadrons.

Like the other services, the Navy and Marine Corps also 

contain large numbers of support or administrative units. 

The vast majority of the Navy’s support units exist to support combat operations by ships and their aircraft, and 

the vast majority of the Marine Corps’ support units exist 

to support combat operations by MEFs. Nearly all of the 

administrative units in the Department of the Navy are 

responsible for creating and maintaining the Navy’s and 

Marine Corps’ combat and support units.3

The Department of the Navy’s forces are distinctive not 

only for their number and variety of units but also for the 

way in which different types of forces routinely work 

closely together. The Army and Air Force each essentially 

focus on a single type of military power (ground combat 

or air combat), but the Navy and Marine Corps routinely 

integrate ships with aircraft (as in carrier strike groups), 

ships with ground combat units (as in amphibious ready 

groups), and aircraft with ground combat units (as in 

Marine expeditionary forces). Although all U.S. forces are 

expected to be able to operate jointly with other services, 

the routine and habitual integration of different types of 

military power within DoN goes beyond typical joint 

operations. For example, the Marine Corps has fewer 

artillery units to support its ground combat units than 

the Army does, in part because the Corps prefers to provide additional firepower (fire support) for its combat 

units by using its attack aircraft—aircraft that may well 

be based on Navy ships. In contrast, the Army has traditionally structured itself on the assumption that it must 

have substantial artillery capability in case Air Force 

aircraft are not available to provide fire support.

Besides conventional warships, MEFs, and forces organized in support of those units, the Navy and Marine 

Corps contain a number of smaller organizations that 

provide some highly specialized military capabilities. 

Prime examples include the Navy’s fleet of ballistic missile 

submarines; its fleet of maritime patrol aircraft, which 

patrol the oceans from land bases; special-operations 

forces, such as the Navy’s Sea, Air, and Land forces 

(known as SEALs); and construction battalions (known 

as Seabees). The Department of the Navy is also responsible for the U.S. sealift fleet, cargo ships that are used to 

transport equipment to overseas operations. Those ships, 

however, are largely operated by civilians employed by 

Military Sealift Command, and their operations are 

funded through revolving funds that are intended to let 

other organizations in the Department of Defense “pay” 

for their sealift needs using accounting credits internal to 

DoD.4

Distribution of Navy and Marine Corps Personnel

The Department of the Navy has roughly 600,000 military personnel, making it less than two-thirds the size of 

the Army. According to the department’s plans for the 

2017–2021 period, almost the same number of personnel 

will be in units devoted to overhead functions as in combat units; the smallest share will be in units that support 

3. As noted in Box 1-1 on page 10, “support” can have a wide variety 

of meanings in military contexts. In this report, “support units” 

are units that would generally be used to provide support to major 

combat units. For example, although Marine Corps combat 

troops could be called on to defend a base being built by Navy 

engineers (as happened to some extent on the Pacific island of 

Guadalcanal during World War II)—and thus the combat troops 

could be said to be supporting the engineers—in general, Navy 

engineers are considered support units.

11 11

Carrier Air Wings 10 10

104 125

51 51

33 33

24 24

8 8

2017 2021

Reserve component

Aircraft Carriers

Surface Combatants

Attack Submarines

Amphibious Ships

Marine Corps Infantry Battalions

Active component

4. Many of the Navy’s fleet replenishment ships, which provide fuel 

and other supplies to ships on deployments, are also operated by 

civilians. However, in this analysis, CBO treats those replenishment ships as part of the indirect support for combat ships.
CHAPTER 3: DEPARTMENT OF THE NAVY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 47

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Table 3-2.

Average Distribution of the Department of the 

Navy’s Military Personnel, 2017 to 2021

Number of Personnel

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

Numbers may not add up to totals because of rounding.

a. “Overhead” refers to administrative units as well as to personnel not 

assigned to any unit.

combat units. (See Table 3-2; because of how closely 

interwoven the Navy and Marine Corps are, that table 

shows totals for DoN as a whole rather than attempting 

to artificially separate the two services.)

Compared with the Army and the Air Force, DoN’s 

forces include a relatively small number of reservecomponent units, and those units are not tightly 

integrated into the operations of their respective activecomponent units. Instead, they serve largely as an 

additional pool of units that can be tapped in special 

circumstances.

In this report, the number of direct personnel that CBO 

estimates for a given type of ship generally reflects the 

average number of Navy personnel that would be 

required to man such a ship for one year, not the number 

of billets on that type of ship. Although an individual 

ship being deployed has a fairly specific number of billets 

on board, the average number of personnel that the Navy 

needs to man a ship is influenced by several other factors. 

For example, ships are not deployed continuously and 

often have a reduced crew while in port or in dry dock for 

maintenance. In those instances, ships may require fewer 

personnel than they have billets. Conversely, some types 

of Navy ships are operated using a dual-crewing system, 

with two sets of crews for the same ship, and thus require 

more personnel than a single crew’s worth of billets. 

Command Levels and Units

Navy ships are deployed either alone or in groups organized by task. The most common groups are carrier strike 

groups and amphibious ready groups, the two types of 

units that form the central organizational structures for 

the Navy.5

 CSGs are built around a single aircraft carrier 

and its air wing and generally include five or six surface 

combatants and an attack submarine. Broadly speaking, 

the other ships in the group are intended to protect the 

aircraft carrier from attack, with the air wing providing 

the group’s offensive power (although those other ships 

also have offensive weapons, and the air wing also has 

defensive capabilities). ARGs consist of three amphibious 

ships to carry personnel, equipment, and the amphibious 

craft used to land forces on shore. The ships in an ARG 

consist of one large-deck amphibious ship (which also 

holds helicopters and aircraft) and two dock ships.

Rather than being deployed at all times, Navy ships progress through an operating cycle of deploying and returning 

to their home ports, undergoing maintenance, training 

new crews, and then deploying again. As a result, only a 

fraction of ships are actually deployed at any one time—

typically, about 30 percent to 40 percent (depending on 

the type of ship, home port, and deployment location), 

although, when necessary, the Navy can increase that number in relatively short order. The Navy generally considers 

the number of ships deployed—its “forward presence”—

to be a more meaningful measure of its contribution to 

national defense than the total number of ships in its fleet.6

Marine Corps ground units are organized in largely the 

same recursive pattern as Army units, with largely the 

same command levels (described in Box 2-1 on page 19). 

The main differences are that the Marine Corps prefers 

the term “regiment” to “brigade,” lacks corps- and 

theater-level commands, and organizes its forces for 

combat in a different manner. Instead of grouping regiments into organizations similar to Army brigade combat 

teams and supporting them with units (such as airsupport and logistics units) from higher command levels, 

the Marine Corps’ practice when deploying for combat 

operations is to assemble task forces with ground 

combat forces, air combat forces, and logistics units as 

Combat Units 210,000 34,000 244,000

Support Units 93,000 25,000 118,000

Overheada _

202,000 38,000 240,000 _______ _______ ________

Total 505,000 97,000 602,000

Active Reserve

Component Component Total

5. In addition, the Navy and Marine Corps have occasionally 

employed expeditionary strike groups, which are essentially ARGs 

with some additional surface combatants and an attack submarine 

included.

6. For a more thorough discussion of the Navy’s forward presence, 

see Congressional Budget Office, Preserving the Navy’s Forward 

Presence With a Smaller Fleet (March 2015), www.cbo.gov/

publication/49989.
48 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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appropriate for the specific operation, as well as a headquarters element for the whole task force. 

The major types of Marine Corps organizations are differentiated by the size of their ground combat component: A Marine expeditionary unit (MEU) is based on 

an infantry battalion and has about 2,200 personnel, a 

Marine expeditionary brigade (MEB) is based on an 

infantry regiment and has about 12,000 personnel, and a 

Marine expeditionary force is based on an infantry division and has about 50,000 personnel. Those infantry 

components are supplemented with other ground combat 

elements; for example, a MEU is not simply an infantry 

battalion but typically includes a platoon of tanks. The 

sizes of the air combat and logistics elements are scaled 

to the sizes of the ground combat component and the 

mission.

Both the Army and the Marine Corps have units that are 

organized permanently and units that are organized specifically for deployments, but the latter are much more 

common in the Marine Corps. The only Marine task 

forces that are permanently organized are MEFs; unless 

they are deployed, MEUs and MEBs are simply small 

headquarters elements with no other forces assigned 

to them. That practice can lead to some ambiguity: In 

different contexts, the term MEU can refer to a headquarters with no other units attached, to a specific task 

force assembled for a specific deployment, or to the general 

idea of a task force based around an infantry battalion—

the sense in which the term is used in this report. Likewise, the fact that MEUs and MEBs are largely created on 

an ad hoc basis using units drawn from MEFs leads to 

some confusion about the total number of Marine Corps 

units. 

Because of such differences in organization, direct comparisons between Army and Marine Corps units are difficult. Whereas Army units typically receive much of their 

support from higher echelons (division-, corps-, and 

theater-level assets), Marine Corps units are constructed 

as integrated task forces that include all of their essential 

support elements. As a result, a Marine task force is much 

larger than a comparably sized Army unit would be. In 

addition, the Army primarily employs brigade combat 

teams, whereas the Marine Corps more commonly uses 

MEFs and MEUs—the MEB, which is roughly equivalent in size to a brigade combat team, is a largely theoretical construct. If the two services used comparably sized 

units and if both treated supporting units as integral to 

their combat units, Army and Marine Corps units would 

be roughly similar in size and capability.7

Like the other military services, the Navy and Marine 

Corps differentiate between the total number of fixedwing aircraft they possess and the number of official 

“slots” for those aircraft in their force structure. For example, a squadron of 12 aircraft is intended to be able to 

operate that many aircraft at all times (in other words, it 

has 12 slots, called the primary aircraft authorization). 

But it may have more aircraft assigned to it (called the 

primary mission aircraft inventory) so the squadron can 

continue to operate at full strength even if some of those 

aircraft require extended maintenance or are otherwise 

unavailable. Similarly, the services have many aircraft that 

are not assigned to combat units—some are at maintenance depots, some are assigned to training squadrons, 

and some may be in storage to serve as replacements if 

aircraft are lost in the future. For those reasons, a service’s 

total aircraft inventory is greater than its primary aircraft 

authorization levels. (For instance, the United States purchased 160 EA-18G electronic attack aircraft but maintains about 95 slots for EA-18Gs in the force structure.) 

In this report, all aircraft numbers represent primary 

aircraft authorizations.

Strengths and Limitations of Navy and 

Marine Corps Forces

The many different types of units that are part of the 

Department of the Navy have their own strengths and 

weaknesses (as described in the sections below about 

major elements of the force structure). But as a whole, 

those units constitute a highly capable force. The Navy’s 

surface combatants, for example, are widely considered to 

be exceptionally powerful units—generally larger, with 

bigger and more capable loads of weapons, and with 

more sophisticated sensors and electronics than the surface combatants of any other navy. Those ships often 

escort the Navy’s aircraft carriers, which are also larger, 

with a greater complement of aircraft, than those of any

7. Many other differences between the two services’ units would 

remain, however. For instance, the Army has no fixed-wing combat aircraft, whereas the Marine Corps has a large inventory of 

such aircraft. (The Army is prohibited from having fixed-wing 

combat aircraft by interservice agreements drawn up shortly after 

the Air Force was created from the Army Air Corps in the 1940s. 

However, the Army uses fixed-wing aircraft for purposes other 

than combat, such as reconnaissance and transport.) 
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other navy.8

 The vast majority of other navies in the 

world resemble the U.S. Coast Guard more than they 

do the U.S. Navy, in that they focus on patrolling their 

country’s coastlines rather than on projecting power overseas. With the probable exception of China’s navy in the 

western Pacific Ocean, no other nation’s navy appears 

intended to challenge U.S. naval supremacy. Perhaps as 

a result, the United States has not faced any significant 

naval combat since World War II (although the Soviet 

navy was prepared to engage U.S. and NATO naval 

forces during the Cold War).

For its part, the Marine Corps—though smaller than the 

Army—is considered one of the most capable ground 

combat organizations in the world. Similarly, DoN’s fleet 

of aircraft—though smaller than the Air Force—is 

thought to be one of the world’s most capable air combat 

organizations. Both of those forces have been used extensively in U.S. combat operations since World War II.

Because the Department of the Navy includes what are 

effectively among the world’s largest and most powerful 

air forces and armies, the department’s naval operations 

have a combined-arms character. Most DoN missions or 

operations include contributions from the department’s 

ships, aircraft, and Marine Corps ground forces. Moreover, the United States has faced no serious naval threats 

since the end of the Cold War in the early 1990s, so in 

major conflicts since then, Navy and Marine Corps units 

have been used almost exclusively to influence ground 

operations or events ashore. Aircraft and Marine ground 

units are often DoN’s most powerful tools for influencing 

events on land, which highlights the flexibility of the 

department’s capabilities.

In the past, the United States has generally had a lower 

threshold for using air and naval forces in combat than 

for using ground forces. Naval forces can be stationed in 

international waters—and thus do not require cooperation from other countries—but are still capable of 

launching air strikes or cruise missile strikes against 

potential targets.9

 In addition, they can respond rapidly, 

provide a relatively visible threat, and are fairly well protected from any reprisals (both by distance from shore 

and by their own defensive weapons). For those reasons, 

naval forces have often been the United States’ preferred 

first option in crisis situations or in smaller interventions. 

In such situations, the United States has sometimes also 

employed amphibious ready groups, whose ability to land 

ground combat units on shore can heighten the perceived 

threat of a U.S. invasion. (However, the relatively small 

size of the ground combat forces included in an ARG—

one combat battalion, with air and logistics support—

makes their use as a threat credible only against fairly 

weak opponents.)10

Using naval forces (or the Air Force) to conduct air and 

cruise missile strikes on opposing states, without also 

committing ground combat forces, has had mixed results 

in achieving the United States’ goals. In some cases—

such as operations against Libya in the 1980s and Serbia 

in the 1990s—air and cruise missile strikes may have 

been enough to achieve U.S. aims. But in many other 

cases—including the U.S. bombing of North Vietnam 

during the 1960s and 1970s and U.S. cruise missile 

attacks against Afghanistan and Sudan in 1998 (Operation Infinite Reach)—aerial campaigns without the use of 

ground forces did not prove effective at accomplishing 

U.S. goals. (For a discussion of those and other past military operations, see Appendix C.)

By comparison, the United States has generally been successful in modern times in using amphibious forces to 

invade opposing countries. Only small and less capable 

states are vulnerable to an entirely amphibious invasion, 

however; in recent decades, the United States has taken 

part in few operationally significant amphibious assaults 

against major opponents.11 In major conflicts with such 

8. The difference in size and capability between U.S. and other aircraft carriers is so great that most other nations’ aircraft carriers 

are, in fact, more comparable to U.S. amphibious assault ships 

(which the Navy does not call aircraft carriers).

9. Cruise missiles are essentially small, unmanned, single-use aircraft 

that have wings, carry a warhead, and fly at the same altitudes as 

manned aircraft (as opposed to ballistic missiles, which are guided 

rockets that loft their warheads high in the atmosphere or above 

the atmosphere).

10. As an alternative, during the planned invasion of Haiti in the 

1990s (referred to as Operation Uphold Democracy), the United 

States deployed an Army division aboard two aircraft carriers. 

That force, much larger than an ARG, created a very credible 

invasion threat that may have contributed to the Haitian government’s acceptance of U.S. demands.

11. Before the Marine Corps began using helicopters as part of its 

amphibious force, only coastal areas were vulnerable to U.S. 

amphibious invasions. That is no longer the case—for example, 

the Marines participated in the invasion of land-locked Afghanistan in 2002—although some areas located far inland remain 

unreachable by U.S. amphibious forces.
50 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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opponents (including the 1991 and 2003 wars with Iraq), 

the Marine Corps was deployed in essentially the same 

manner as the Army—as an additional ground force—

rather than conducting an amphibious assault. The 

Marine Corps’ amphibious capability has been used most 

in some of the Corps’ least demanding operations, 

including peacetime missions and operations against 

opponents such as Grenada or Somalia, which were not 

capable of presenting concerted resistance.

DoD believes that the most likely future scenarios for 

U.S. naval combat involve operations conducted close 

to an enemy landmass. Such “littoral” operations pose 

special challenges for naval forces: They allow an enemy’s 

land-based forces to affect naval operations (for example, 

by attacking ships with land-based aircraft or missiles), 

while making it harder for naval forces to respond (for 

instance, by limiting their ability to maneuver, making it 

more difficult for them to find and destroy targets, and 

exposing them to mines such as those that damaged the 

USS Princeton and USS Tripoli during the 1991 war with 

Iraq). A potential conflict between the United States and 

China over the status of Taiwan, for example, would most 

likely involve China using land-based aircraft, cruise missiles, and ballistic missiles to try to keep the Navy out of 

the immediate area of operations. And a potential conflict 

in the Strait of Hormuz would most likely see Iran using 

submarines and land-based cruise missiles to try to deny 

Navy and commercial ships safe passage through the 

narrow waters of the strait (see Appendix C).

The lack of significant naval threats for the past two 

decades and the fact that, in major conflicts, Navy and 

Marine Corps units have usually been used to affect operations on land have led analysts to differing conclusions. 

Some argue that if the United States had invested fewer 

resources in naval forces and more in ground and air 

forces, it would have had more effective combat power 

at its disposal in all of its major combat operations since 

World War II. Other analysts, however, assert that the 

United States has not faced any major naval competitors 

precisely because the U.S. Navy’s power has deterred 

other nations from having naval ambitions (because 

building a fleet capable of competing with the U.S. Navy 

would be prohibitively expensive). Still others point out 

that the United States, unlike its adversaries, has been 

able to enjoy the benefits of uncontested control of 

the sea lanes, such as the ability to use cargo ships to 

transport ground forces to distant theaters of operations. 

Those benefits from deterrence and control of the sea 

lanes may be greatest when the U.S. Navy is most dominant, meaning that some of the advantages of naval 

dominance may not be readily apparent, despite their 

importance. (Many proponents argue that the deterrent 

effect of U.S. naval power provides a significant global 

public good by suppressing naval competition between 

other countries and ensuring freedom of navigation for 

civilian shipping.)

In addition to their roles during conflicts, naval forces 

perform a variety of peacetime missions. For example, 

they are routinely used to evacuate noncombatants from 

conflict zones, to provide humanitarian and disaster 

relief, and to conduct antipiracy patrols. Some advocates 

of naval forces also suggest that the Navy, by being physically present in distant locations around the world, provides a form of visible U.S. presence that is more effective 

at reassuring friends and allies about U.S. security commitments—and at deterring U.S. opponents—than are 

Army and Air Force units, which are often farther away. 

The vast majority of the Navy’s operations today are routine deployments of ships around the globe to provide 

that presence.

What This Chapter Covers

The rest of this chapter presents CBO’s analysis of the 

following major elements of the Navy’s and Marine 

Corps’ force structure (listed here with the percentage of 

the Department of the Navy’s O&S costs that they 

account for):

B Aircraft carriers (21 percent); see page 52.

B Surface combatants (14 percent); see page 56.

B Attack submarines (7 percent); see page 59.

B Amphibious ships (9 percent); see page 61.

B Marine Corps infantry battalions (33 percent); see 

page 65.

B Other units and activities of the department 

(16 percent), such as ballistic missile submarines, 

construction engineers, and special-operations forces; 

see page 68.
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This chapter also examines four topics of special concern 

to the Department of the Navy:

B The integration of the Navy and Marine Corps; see 

page 70. 

B The ability to conduct forcible-entry operations 

(which involve gaining access to enemy territory that 

cannot be reached from adjacent land areas); see 

page 72.

B The types of aircraft used by the Navy; see page 74. 

B The types of aircraft used by the Marine Corps; see 

page 77.
52 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Aircraft Carriers

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

Aircraft carriers serve as platforms for flight operations by 

their air wings and also form the nucleus of carrier strike 

groups, or CSGs. (See Figure 3-1 on page 54 for the size 

and organization of a CSG.) All of the Navy’s current and 

planned aircraft carriers are nuclear powered, meaning 

that they can operate for long periods without needing to 

be refueled. In addition, all of them are large enough and 

have the necessary design features to allow sustained air 

operations by fixed-wing aircraft that are not capable of 

performing short takeoffs and vertical landings. (Those 

design features include catapults to launch aircraft, 

arresting wires to stop planes when they land, and 

angled decks.)12 On its own, an aircraft carrier has a 

limited ability to defend itself from attacks by missiles, 

aircraft, submarines, or other ships. Its air wing and the 

other ships in its CSG are responsible for helping to 

defend the carrier.

The majority of the aircraft in a carrier air wing are 

F/A-18 multirole fighters, which are capable of defending 

against aerial threats as well as attacking targets at sea or 

on land.13 Those fighters are comparable in most respects 

to the Air Force’s tactical aircraft and can carry most of 

the advanced munitions that Air Force strike aircraft do. 

The rest of the aircraft in a carrier air wing largely support the operations of the carrier and the F/A-18s. 

Current and Planned Structure. The Navy will field 

11 aircraft carriers and 10 carrier air wings in 2017.14 In 

its 2017 budget request, it indicated no plans to change 

the number of carriers through 2021, although it proposed eliminating one carrier air wing.15 Each air wing 

consists of eight squadrons of fixed-wing aircraft and 

helicopters. Together, the Navy’s aircraft carriers and 

associated air wings account for about 21 percent of the 

Department of the Navy’s total operation and support 

funding.

Purpose and Limitations. The Navy’s carrier force gives 

the United States the ability to strike a wide variety of targets across the world by air, particularly in places where 

the U.S. military does not have its own air bases on land 

or access to other countries’ air bases. The range of Navy 

fighter aircraft (and the ability to use aerial refueling) 

Military Personnel per Unit 6,590 3,200 760 2,620

Annual Cost per Unit 1,180 470 180 530

(Millions of 2017 dollars)

Military Personnel per Unit 4,860 1,630 1,300 1,930

Annual Cost per Unit 910 330 200 390

(Millions of 2017 dollars)

Total Direct Indirect Overhead

Aircraft Carrier

Carrier Air Wing

12. The majority of the world’s aircraft carriers do not have those 

features and more closely resemble the Navy’s LHA amphibious 

assault ships. They are smaller, not nuclear powered, and do not 

have catapults, arresting wires, or angled decks, so they are only 

capable of operating a smaller air wing that consists of helicopters 

and specialized short-takeoff, vertical-landing aircraft.

13. The Navy is currently purchasing the C model of the F-35 Joint 

Strike Fighter to replace the older C and D models of the F/A-18. 

14. When this report was published, the Navy had 10 active carriers 

because of a gap between the retirement of the USS Enterprise and 

the commissioning of the USS Gerald R. Ford. For a detailed 

discussion of the Navy’s shipbuilding plans, see Congressional 

Budget Office, An Analysis of the Navy’s Fiscal Year 2016 Shipbuilding Plan (October 2015), www.cbo.gov/publication/50926.

15. The Navy plans to keep the aircraft associated with that wing by 

distributing them to other air wings.
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means that carrier air wings can strike targets relatively far 

inland, not just along coasts. In addition, the mobility 

of aircraft carriers allows the United States to reposition 

them to assist in almost any likely combat scenario. 

Experience has also shown that carrier-based aircraft are 

among the most powerful antiship weapons and that 

surface combatants exposed to attack from aircraft are 

extremely vulnerable (although the United States has not 

had many occasions to use that capability since World 

War II).

The main limitation of the carrier force is that carrier aviation is a relatively expensive way to employ tactical aircraft in operations in which air bases on land are available 

to the United States. The U.S. military has invested heavily in naval aircraft and has used them in every major 

conflict since World War II (at times, perhaps, because 

the assets existed rather than because they were the only 

assets that could perform a particular mission). In many 

of those conflicts, however, the unique value of aircraft 

carriers—to provide bases in otherwise inaccessible locations—was not fully demonstrated because the United 

States had access to air bases on land for at least part of 

the conflict.16

A possible further drawback of aircraft carriers is that 

during combat operations, they could face a number of 

threats that might make them vulnerable, despite the 

defensive capabilities of the other ships in a strike group. 

Navy ships have not faced sustained attacks since World 

War II, however, so it is difficult to assess how vulnerable 

aircraft carriers would be in a conflict in which they came 

under heavy attack from aircraft, cruise missiles, ballistic 

missiles, or submarines. Analysts have long debated how 

well aircraft carriers could survive attack in a contested 

naval environment (such as was possible in a conflict with 

the Soviet Union or might be possible in a future conflict 

with China). 

Although no adversary has successfully attacked a U.S. 

carrier since 1945, the importance of aircraft carriers for 

the United States’ ability to project power has created 

strong incentives for hostile states to develop weapons 

and tactics to counter those ships and their aircraft. For 

example, some states are developing high-speed antiship 

cruise missiles and antiship ballistic missiles in an effort 

to penetrate the air defenses of carrier strike groups. In 

turn, the emergence of those more sophisticated weapons 

has led the Navy to develop responses, including 

improvements in air and missile defenses.

Past and Planned Use. For more than 70 years, the 

United States has used carrier-based aircraft in all of its 

major combat operations as well as in a number of 

smaller operations (see Appendix C). In many cases, 

those aircraft have been the most rapid and flexible form 

of military response available to the United States. Aircraft carriers have also been employed, though to a much 

more limited degree, for some nontraditional missions, 

such as disaster response. In addition, plans for a U.S. 

invasion of Haiti in the mid-1990s (called Operation 

Uphold Democracy) envisioned using two aircraft carriers as bases for an air assault by an Army division, with 

the division’s helicopters taking the place of the carriers’ 

normal air wings. (The invasion was never carried out 

because a diplomatic solution to the crisis was found.) 

The U.S. military seems likely to continue to use aircraft 

carriers in future conflicts, unless a potential adversary 

proves capable of presenting an unacceptably dangerous 

threat to carrier strike groups (as some analysts believe 

China might in a future conflict in the South China Sea).

The Navy’s goals for the size of the carrier fleet are based 

on its analysis of wartime scenarios as well as on its goals 

for having ships deployed overseas (providing what is 

commonly called forward presence). In major U.S. military operations since the end of the Cold War—such as 

the conflicts in Kuwait in 1991, in Afghanistan in 2001, 

and in Iraq in 2003—the Navy eventually provided five to 

seven aircraft carriers. Maintaining a fleet of 11 carriers 

would usually allow 5 of them to be available within 30 days 

for a crisis or conflict (the rest would be undergoing scheduled maintenance or taking part in training exercises and 

would be unready for combat). Within 90 days, the Navy 

would generally have seven carriers available. A larger 

carrier force would be able to provide more ships for a 

conflict, and a smaller force fewer.

16. In some instances, even if the United States has access to air bases 

on land, the bases do not have enough capacity to support an 

entire U.S. air operation. In such cases, having carrier aviation 

allows the United States to station more tactical aircraft in a theater of operations than it would otherwise be able to do. (That 

advantage tends to diminish over the course of a long conflict, 

however, because Air Force engineers can substantially improve 

the size and capability of friendly nations’ air bases.) Aircraft carriers can also provide the United States with flexibility in cases in 

which regional governments do not allow U.S. forces to freely use 

local air bases or travel through local airspace.
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Figure 3-1.

Ships, Aircraft, and Personnel in a Navy Carrier Strike Group

Continued

During peacetime, the carrier fleet conducts routine 

patrols around the world, providing forward presence to 

reassure the United States’ friends and allies and deter 

potential aggressors. Given the Navy’s normal operating 

cycles for ships and crews, the current force of 11 carriers—one of which is based in Japan—can provide the 

equivalent of two carriers deployed year-round and a 

third carrier deployed for eight months of the year. (At 

any given time, the other carriers are transiting to or from 

their deployment areas, engaging in training activities, 

undergoing routine maintenance, or being overhauled.) 

Having more carriers, longer deployments, or more carriers based overseas would increase the fleet’s capability to 

provide forward presence, whereas having fewer carriers 

or shorter deployments, or withdrawing the carrier based 

in Japan, would decrease that capability.17

CVN-68 Nimitz Class 

Aircraft Carrier 

F/A-18E/F 

Fighter/Attack 

Aircraft

F/A-18C

Fighter/Attack 

Aircraft

EA-18G Electronic Attack Aircraft

E-2C Surveilance

Aircraft

C-2 Transport Aircraft

H-60 Utility 

Helicopters

17. For a more thorough discussion of the Navy’s forward presence, 

including deployment cycles and approaches to increase forward 

presence, see Congressional Budget Office, Preserving the Navy’s 

Forward Presence With a Smaller Fleet (March 2015), 

www.cbo.gov/publication/49989. 
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Figure 3-1. Continued

Ships, Aircraft, and Personnel in a Navy Carrier Strike Group

Source: Congressional Budget Office, using data from the Department of Defense.

The number of personnel shown here for the various ships reflects the Navy’s official crew size (number of billets) for each type of ship rather than (as in 

the entries for those ships) the average number of personnel that would be required to man such a ship for one year.

0 100 300 400 500 feet 200

= 100 Personnel = 10 Personnel

DDG-51 Arleigh Burke Class Destroyer

SSN-688 Los Angeles Class Attack Submarine

DDG-51 Arleigh Burke Class Destroyer

CG-47 Ticonderoga Class Cruiser 

CG-47 Ticonderoga Class Cruiser 

DDG-51 Arleigh Burke Class Destroyer

LCS-1 Freedom Class Littoral Combat Ship 
56 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Surface Combatants

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

The Navy divides its fleet of surface combat ships into 

large surface combatants (destroyers and cruisers) and 

small surface combatants (littoral combat ships and 

FFG-7 frigates, a type of ship the Navy retired in 2015). 

The larger combatants are powerful ships equipped with 

the Vertical Launch System (VLS), which allows them to 

use several different kinds of missiles to attack targets in 

the air, at sea, or on land. The smaller combatants do not 

have the VLS but instead carry a variety of smaller and 

more specialized weapons intended mainly for defensive 

purposes, particularly antisubmarine warfare. Most of the 

Navy’s surface combatants carry one or two SH-60 

Seahawk helicopters to assist in various missions.

Since World War II, the Navy’s surface combatants have 

evolved from being vessels distinguished primarily by the 

size of their main guns—which in turn largely determined the size of the ships—to being versatile platforms 

for several weapon systems. Since the introduction of the 

VLS in the early 1980s, the Navy’s large surface combatants have been differentiated mainly by their sensors and 

intended combat specialties rather than by their size or 

type of weapons. Ships equipped with the VLS can carry 

an interchangeable set of standard munitions, including 

Tomahawk cruise missiles, ASROC antisubmarine weapons, and Standard air-defense missiles. (Such ships can 

also carry Harpoon antiship missiles, which use a launch 

system other than the VLS.) In addition, the Navy has a 

limited number of Standard missiles that can intercept 

short- and medium-range ballistic missiles, although that 

number is expected to grow. Similarly, the Navy’s small 

surface combatants have become versatile ships primarily 

intended to defend larger ships against attack by submarines and small boats and to replace the Navy’s mine 

countermeasures ships. All of the Navy’s surface combatants have enough defensive capability that they can 

operate independently during normal peacetime 

deployments.

Current and Planned Structure. In 2017, the Navy will 

field 104 surface combat ships of various sizes, including 

DDG-51 and DDG-1000 destroyers, CG-47 cruisers, 

Military Personnel per Unit 720 340 100 290

Annual Cost per Unit 140 60 20 60

(Millions of 2017 dollars)

Military Personnel per Unit 550 250 90 220

Annual Cost per Unit 110 40 20 40

(Millions of 2017 dollars)

Military Personnel per Unit 430 190 70 170

Annual Cost per Unit 100 40 20 30

(Millions of 2017 dollars)

Military Personnel per Unit 500 220 80 200

Annual Cost per Unit 100 40 20 40

(Millions of 2017 dollars)

Total Direct Overhead Indirect

Arleigh Burke Class Destroyer (DDG-51)

Ticonderoga Class Cruiser (CG-47)

Littoral Combat Ship

Zumwalt Class Destroyer (DDG-1000)
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and littoral combat ships (LCSs). That total number is set 

to increase to 125 by 2021 as new DDG-51s, DDG1000s, and LCSs are added to the fleet.18 Together, 

surface combatants account for about 14 percent of the 

Department of the Navy’s total operation and support 

funding.

Purpose and Limitations. A large share of the Navy’s 

surface combatants are used in carrier strike groups to 

protect aircraft carriers. Although numbers vary at times, 

a carrier strike group generally includes five or six surface 

combatants, in addition to the carrier and an attack submarine. Surface combatants could also be used to escort 

and defend amphibious ready groups in some scenarios, 

but it is not currently normal peacetime practice for the 

Navy to deploy surface combatants with those groups. 

In addition, surface combatants are frequently deployed 

on their own or in small groups (called surface action 

groups) either to defend an area against ballistic missiles 

or to allow the Navy’s limited number of ships to provide 

a greater amount of forward presence in places of interest 

to the United States. Missile defense missions and forward presence missions are similar in many respects, 

though they differ in some ways. In both cases, the 

essence of the deployment is simply to be available in 

some area. However, the Navy’s ability to carry out missile defense missions depends on the limited number 

of large surface combatants that have ballistic missile 

defense capability, and the locations of those missions 

are determined by the possible flight paths that missiles 

could travel between an adversary and its potential 

targets.

The main limitation of surface combatants is that they 

have less capability than aircraft carriers or amphibious 

ships to affect ground combat operations, which have 

dominated the major conflicts in which the United States 

has engaged for the past 70 years. Although large surface 

combatants can launch Tomahawk cruise missiles, the 

Navy has a significant capability to fire cruise missiles 

from other vessels (such as attack and guided missile 

submarines), and most U.S. combat operations rely on 

tactical aircraft for the vast majority of strikes on ground 

targets.19 Surface combatants also have guns that can provide firepower, but those guns have relatively short 

ranges, which severely limits their ability to affect combat 

operations on land. The DDG-1000 class of destroyers 

that the Navy is commissioning will have an advanced 

gun system with a longer range than other naval guns in 

the fleet today, but in many scenarios that range will still 

not be long enough to make a significant contribution to 

ground combat. (In addition, the Navy plans to buy only 

three DDG-1000 destroyers, so the availability of those 

longer-range naval guns will be quite limited.)

In general, surface ships face a number of potential 

threats in naval combat operations that might make them 

vulnerable. However, because the United States has 

engaged in very little naval combat since World War II, it 

is difficult to gauge how vulnerable the Navy’s surface 

ships would be if they came under heavy attack from aircraft, cruise missiles, ballistic missiles, or submarines. 

Some events—such as the war between the United Kingdom and Argentina over the Falkland Islands in 1982 and 

the attack on the USS Stark by a missile launched from 

an Iraqi jet in 1987—suggest that surface ships may be 

extremely vulnerable to modern weaponry. Moreover, 

during Operation Desert Shield in the early 1990s, two 

U.S. surface combatants hit Iraqi mines, which suggests 

that older naval mines can be effective against Navy ships. 

Similarly, in 2000 a boat filled with explosives attacked 

the USS Cole in a port in Yemen, indicating that small 

boats may be capable of inflicting great damage on surface 

combatants operating close to shore (for a discussion of 

those and other past military operations, see Appendix C). 

However, the Navy has taken a number of steps to 

respond to those potential threats, and it is difficult to 

judge how successfully U.S. surface combatants might 

fare in similar situations in the future.

Past and Planned Use. In practice, the most common 

contributions that surface combatants have made to 

U.S. combat operations in recent decades have been as 

platforms for launching Tomahawk cruise missiles to 

18. For a detailed discussion of the Navy’s shipbuilding plans, see 

Congressional Budget Office, An Analysis of the Navy’s Fiscal 

Year 2016 Shipbuilding Plan (October 2015), www.cbo.gov/

publication/50926. In its 2016 budget request, the Navy proposed removing 11 CG-47 cruisers from the fleet, but in the 

National Defense Authorization Act for Fiscal Year 2016, lawmakers prohibited the Navy from eliminating those ships. The 

Navy did not propose removing any CG-47 cruisers from the fleet 

in its 2017 budget request.

19. Cruise missiles are most frequently used at the beginning of a 

conflict, when the United States is typically trying to destroy an 

enemy’s air defenses. Cruise missiles are considered a safer option 

than aircraft for strike missions when enemy air defenses are still 

capable of threatening the lives of U.S. pilots.
58 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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strike targets on land and as protectors of aircraft carriers 

and amphibious ships. Those roles reflect the nature of 

recent conflicts: Iraq and Afghanistan had no significant 

naval forces to engage. In possible future conflicts, however, the ability of U.S. cruisers and destroyers to provide 

missile defense and air defense could be significant. For 

example, scenarios involving possible future conflicts 

between the United States and China over the status of 

Taiwan would probably require the Navy’s large surface 

combatants to defend Taiwan from attack by ballistic 

missiles and to defend U.S. carriers from attack by aircraft, ballistic missiles, and cruise missiles. Similarly, scenarios involving attempts by Iran to restrict shipping 

through the Strait of Hormuz would probably require 

that large surface combatants defend against aircraft and 

missiles and that surface combatants of all sizes defend 

against submarines and small boats (see Appendix C). 

Analyses of such wartime scenarios have led the Navy to 

set a goal of having 88 large surface combatants. 

Although a significant portion of the Navy’s cruisers and 

destroyers are dedicated to protecting aircraft carriers, 

they also carry out a variety of independent operations 

and other missions, such as providing regional ballistic 

missile defense in Europe and Northeast Asia. Major 

reductions in the force of large surface combatants (without similar reductions in the force of aircraft carriers) 

might imperil the Navy’s ability to provide escorts to 

carriers, but small or moderate changes to the number of 

large surface combatants would not, although they might 

affect the Navy’s ability to conduct other missions or to 

provide forward presence in peacetime.

With a planned force of 88 large surface combatants—

including 9 based in Japan and 4 based in Spain—

the Navy could have approximately 28 of those ships 

operating in overseas areas at any one time, given its 

normal operating cycle. Buying more ships, conducting 

longer deployments, or basing more ships overseas would 

increase that number, and the reverse would decrease it.20

The Navy’s plans for small surface combatants call for 

having a force of 52 by 2028. With the retirement of 

FFG-7 frigates, that force will consist entirely of littoral 

combat ships—including, in the future, a new class of 

improved LCSs that the Navy plans to designate as frigates. LCSs (and the future frigates) use a scheme of rotating crews that would allow the Navy to keep 26 of those 

52 small surface combatants forward deployed at any 

given time. 

20. For a more thorough discussion of the Navy’s forward presence 

and the factors that affect it, see Congressional Budget Office, 

Preserving the Navy’s Forward Presence With a Smaller Fleet

(March 2015), www.cbo.gov/publication/49989. 
CHAPTER 3: DEPARTMENT OF THE NAVY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 59

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Major Element of the Force Structure

Attack Submarines

Because of data limitations, the Congressional Budget Office could not estimate costs for different classes of attack submarines using the framework of 

this analysis.

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

The Navy’s attack submarines are large vessels powered by 

nuclear reactors, which allow them to operate underwater 

for long periods with no practical limits on their range. 

They are armed with a variety of weapons, such as torpedoes for destroying surface ships and other submarines 

and Tomahawk cruise missiles for striking targets on 

land. In addition, some U.S. attack submarines have 

been fitted with specialized equipment allowing them to 

deliver teams of special forces ashore. (Attack submarines 

are not capable of performing some naval missions, such 

as engaging aerial targets or providing missile defense.) 

Current and Planned Structure. The Navy will field 

51 attack submarines (which consist of Los Angeles, 

Seawolf, and Virginia class submarines) in 2017. That 

number is expected to rise to 52 the following year but 

return to 51 by 2020. Attack submarines account for 

about 7 percent of the Department of the Navy’s total 

operation and support funding. (The Navy operates 

other types of submarines, such as ballistic missile and 

guided missile submarines. Those types are discussed in 

an entry, “Other Department of the Navy Units and 

Activities,” on page 68.

Purpose and Limitations. The Navy’s fleet of attack 

submarines evolved largely to ensure the United States’ 

ability to use sea lanes around the world freely for military and civilian shipping during conflicts. For years, that 

fleet’s main adversary was the Cold War–era Soviet navy, 

which built large numbers of submarines in an effort to 

prevent the United States from transporting military 

forces to Europe by ship in the event of a conflict there. 

Another major mission for the Navy’s attack submarines 

was to hunt for and destroy Soviet ballistic missile submarines (those carrying strategic nuclear warheads), 

including submarines operating beneath the Arctic ice 

pack. 

In contrast to the Navy’s nuclear-powered submarines, 

many of the United States’ potential adversaries have diesel electric submarines. Those submarines use diesel 

engines to charge batteries, which can then power the 

submarines for relatively short periods while submerged. 

Diesel electric submarines are often considered best 

suited to coastal defense, for two reasons. First, the need 

to carry diesel fuel limits their range, and second, the 

need for an air supply (generally obtained either by surfacing or by raising an air-intake snorkel periodically) 

limits their ability to stay underwater. Diesel electric submarines can be more tactically effective than nuclear 

submarines, because battery power is quieter underwater 

than a nuclear reactor. That quietness gives diesel electric 

submarines an advantage in detecting, or avoiding detection by, enemy warships and submarines.

The Navy is generally very secretive about its submarine 

operations. Nevertheless, it has asserted that the stealthy 

nature of attack submarines makes them excellent 

intelligence-gathering assets, capable of observing foreign 

nations while undetected. A lack of unclassified information, however, makes it difficult to assess the value of that 

mission or the number of submarines that it requires. At 

the same time, the stealthy nature of attack submarines 

means that they are not useful for providing visible forward presence overseas, except when conducting port 

visits in other countries.

The main limitation of the attack submarine force is that 

it has relatively little ability to directly affect ground combat operations, which have dominated the United States’ 

Military Personnel per Unit 390 190 50 150

Annual Cost per Unit 140 70 40 30

(Millions of 2017 dollars)

Total Direct Indirect Overhead
60 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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military conflicts since World War II. Although attack 

submarines can launch Tomahawk cruise missiles, the 

Navy has an enormous capability to fire cruise missiles 

from other vessels, such as surface combatants and guided 

missile submarines. Moreover, most U.S. combat operations rely on tactical aircraft for the vast majority of 

strikes on ground targets.21 Attack submarines can sometimes be used to deploy special forces covertly, but that 

capability is often more useful in peacetime than during 

major combat operations, when the United States has 

numerous methods for inserting special forces into a theater (including by fixed-wing aircraft or helicopters).

There is little reason to believe that the Navy’s attack 

submarine fleet is particularly vulnerable to any type of 

threat in the current military environment. By their 

nature, submarines are the most difficult types of naval 

vessels to detect and destroy, and the greatest potential 

threat to any submarine is generally another submarine. 

Some analysts have questioned how U.S. attack submarines might perform against advanced diesel electric 

submarines in shallow waters, such as those of the Persian 

Gulf, where diesel electric submarines have some tactical 

advantages. But the United States has various options for 

attacking and defeating such submarines, including landbased patrol aircraft, ship-based helicopters, and surface 

combatants.

Past and Planned Use. In recent decades, the most common roles that attack submarines have played in U.S. 

combat operations have been as platforms for launching 

Tomahawk cruise missiles at ground targets, for conducting surveillance, or for collecting intelligence. However, 

those roles reflect the fact that Iraq and Afghanistan had 

no significant naval forces to engage. In conflicts that the 

United States might face in the future, the ability of 

attack submarines to intercept an enemy’s naval forces 

and commercial shipping close to the enemy’s coastline 

could be important in the conduct of the conflict. For 

instance, scenarios involving conflicts between the United 

States and China over the status of Taiwan could easily 

hinge on the possibility of a Chinese amphibious invasion 

of Taiwan, in which case the ability of U.S. attack submarines to destroy Chinese vessels would be critical. (For 

a discussion of DoD’s planning scenarios for those and 

other areas, see Appendix C.) Similarly, scenarios involving attempts by Iran to restrict shipping through the 

Strait of Hormuz might require U.S. attack submarines 

to destroy Iranian submarines (which would most likely 

be an important part of Iran’s strategy to deny the United 

States access to the Persian Gulf).

On the basis of such wartime scenarios, the Navy’s stated 

goal for the size of the attack submarine force has 

remained at 48 for the past decade. The Navy’s analysis is 

based on classified information, however, so it is not clear 

what effects increasing or decreasing the size of that force 

would have on the Navy’s ability to achieve its wartime 

objectives.22

In peacetime, attack submarines’ main missions are conducting surveillance, gathering intelligence, and supporting carrier strike groups. The Navy aims to have at least 

10 attack submarines deployed overseas at any given time 

for various peacetime operations, which may also include 

supporting the activities of special-operations forces. The 

Navy currently bases three of its attack submarines in 

Guam, although that number will soon rise to four. The 

standard operating cycle for attack submarines—one 

6-month deployment during a 24-month period—means 

that a submarine based in the continental United States is 

deployed overseas for an average of about 3 months per 

year (6 months over two years), whereas a submarine 

based in Guam is deployed overseas for about twice that 

amount of time. The Navy could keep more attack submarines overseas at any given time if it had a larger force, 

deployed submarines for longer periods, or stationed 

more of them at overseas bases. Conversely, a smaller 

force, shorter deployments, or fewer submarines based 

outside the United States would reduce the number of 

attack submarines operating overseas at any one time. 

21. Cruise missiles are most frequently used at the beginning of a 

conflict, when the United States is typically trying to destroy an 

enemy’s air defenses. Cruise missiles are considered a safer option 

than aircraft for strike missions when enemy air defenses are still 

capable of threatening the lives of U.S. pilots.

22. For a detailed discussion of the Navy’s shipbuilding plans, see 

Congressional Budget Office, An Analysis of the Navy’s Fiscal 

Year 2016 Shipbuilding Plan (October 2015), www.cbo.gov/

publication/50926.
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Major Element of the Force Structure

Amphibious Ships

Because of data limitations, the Congressional Budget Office could not estimate costs for different classes of amphibious ships using the framework of 

this analysis. The costs shown here are average costs for ships only (they do not include the costs of the Marine units that would deploy on the ships).

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

As their name implies, amphibious ships are designed to 

conduct operations that involve moving from sea to 

land—specifically, delivering forces into hostile territory 

from friendly ships. The Navy’s amphibious ships generally operate in amphibious ready groups (ARGs), each of 

which is composed of three ships (see Figure 3-2):

B One large-deck amphibious assault ship (an LHA 

or LHD class ship), which is capable of carrying helicopters, tilt-rotor aircraft, and specialized fixed-wing 

aircraft that can perform short takeoffs and vertical 

landings. Those ships also have well decks that allow 

them to launch and recover Navy landing craft and 

Marine Corps amphibious assault vehicles.

B Two dock ships (one LPD and one LSD class ship), 

which have large cargo holds and the ability to launch 

and recover Navy and Marine Corps landing craft and 

amphibious assault vehicles.23

An amphibious ready group is designed to carry a single 

Marine expeditionary unit (MEU), which consists of an 

infantry battalion plus air and logistical support units, 

with a total of about 2,200 personnel and 30 aircraft, 

both rotary-wing (helicopters and tilt-rotors) and fixedwing aircraft.24 Amphibious ships have no meaningful 

offensive capability of their own, but they have the 

capability to defend themselves against aerial and naval 

threats. 

Current and Planned Structure. The Navy plans to field 

33 amphibious ships during the 2017–2021 period—

enough for 10 complete amphibious ready groups now 

and 11 complete groups once an 11th large-deck 

amphibious assault ship is delivered in 2024. (Those figures do not include 2 command ships that are considered 

part of the amphibious fleet in the Department of 

Defense’s Future Years Defense Program.) Amphibious 

ships account for about 9 percent of the Department of 

the Navy’s total operation and support funding.

The Navy’s three main types of amphibious ships vary 

greatly in size and capability. However, data from DoD 

do not distinguish between the different types, so for this 

analysis, CBO reports average values for personnel and 

costs for amphibious ships, even though none of the different types of ships exactly match those average values. 

Nevertheless, because the Navy generally buys amphibious ships in fairly constant ratios of the different types of 

ships, large changes in the number of amphibious ships in 

the fleet will result in the same approximate average cost 

Military Personnel per Unit 1,450 710 170 580

Annual Cost per Unit 270 110 40 120

(Millions of 2017 dollars)

Total Direct Indirect Overhead

23. The two classes of dock ships largely serve the same function, but 

they differ somewhat in their ability to carry equipment and personnel. LPD class ships, which are larger than LSD class ships, can 

carry helicopters or V-22 tilt-rotor aircraft as well as landing craft. 

For more information about the differences between types of 

amphibious ships, see U.S. Navy, “America’s Navy: The Amphibs” 

(accessed March 22, 2016), www.navy.mil/navydata/ships/

amphibs/amphib.asp.

24. Marine expeditionary units are discussed in more detail in the 

entry “Marine Corps Infantry Battalions,” on page 65. Although 

the ships that make up an amphibious ready group carry a MEU 

when they are deployed at sea, it is not correct to infer that there 

is one MEU per ARG. MEUs are not assigned to ARGs when 

they are not deployed, and the Marine Corps maintains 7 MEU 

headquarters, although the Navy can field 10 ARGs. Rather than 

being a fixed set of units, MEUs are task-organized units that are 

primarily composed of units drawn from other Marine Corps 

commands.
62 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Figure 3-2.

Ships, Aircraft, Equipment, and Personnel in a Navy Amphibious Ready Group and a 

Marine Expeditionary Unit

Continued

and personnel requirement for an amphibious ship as 

CBO has estimated. 

Purpose and Limitations. Unlike past amphibious operations, which relied entirely on waterborne landing craft, 

modern operations generally involve delivering personnel 

and equipment to a target area by air as well as by water. 

For smaller operations that do not require transporting 

heavy equipment, ARGs can conduct the entire delivery 

operation with the MEU’s aircraft, giving modern 

amphibious operations much greater range and flexibility 

than past operations. 

ARGs (and their associated MEUs) are also capable of 

performing a wide variety of missions in peacetime. They 

can be used to evacuate embassy personnel and other 

noncombatants from a conflict zone, and they are considered extremely useful for humanitarian assistance, disaster 

response, antipiracy missions, and other types of operations that do not involve major conflicts.

The main limitation of the amphibious force is that a single MEU is not large enough to significantly affect most 

major combat operations. Although several ARGs could 

be combined to land a larger force, the conditions under 

which such a major amphibious operation would be 

necessary are relatively rare. Experience indicates that 

opposed amphibious assaults are extremely dangerous, so 

military planners strongly prefer to conduct them only 

when no better options exist. Other than landing Marine

Amphibious Ready Group

Naval Support 

Element 

0 100 300 feet 200

LSD- 41 Whidbey Island Class Dock Landing Ship

LHD-1 Wasp Class Amphibious Assault Ship

LPD-17 San Antonio Class Amphibious Transport Dock Ship 

= 100 Personnel = 10 Personnel
CHAPTER 3: DEPARTMENT OF THE NAVY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 63

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Figure 3-2. Continued

Ships, Aircraft, Equipment, and Personnel in a Navy Amphibious Ready Group and a 

Marine Expeditionary Unit

Source: Congressional Budget Office, using data from the Department of Defense.

The number of personnel shown here for the various ships reflects the Navy’s official crew size (number of billets) for each type of ship rather than (as in 

the entries for those ships) the average number of personnel that would be required to man such a ship for one year.

Command Element 

Marine Expeditionary Unit 

Aviation Combat Element Logistics Combat Element Ground Combat Element 

Navy– and Marine Corps–Specific Items

AAV7A1 Amphibious 

Assault Vehicle

Landing Craft Air Cushion 

Landing Craft Utility

Mortar

Ammunition

Light Armored Vehicle

AV-8B Attack Aircraft 

CH-53E Heavy-Lift Helicopter 

MV-22 Medium-Lift Tilt-Rotor Aircraft

UH-1Y Light Utility Helicopter

AH-1Z Attack Helicopter

H-60 Utility Helicopter

KC-130J Transport/Tanker 

Aircraft

M1 Tank

LW 155 Lightweight 155 mm 

Howitzer

High Mobility Multipurpose 

Wheeled Vehicle 

Medium Tactical Vehicle

M88A2 Improved 

Recovery Vehicle 

(Hercules)

Bulldozer

Rough Terrain Forklift

M984A1 Heavy Expanded 

Mobility Tactical Truck 

Wrecker

M978 Heavy Expanded 

Mobility Tactical

Truck Fuel Tanker With

Fuel Trailer 

M1161 Internally Transportable Vehicles:
64 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Corps forces, ARGs are capable of offering only minor air 

support in a conflict. ARGs carry far fewer aircraft than 

an aircraft carrier does, and their aircraft have much 

shorter ranges and smaller payloads. (Moreover, as noted 

above, even carrier-based aircraft tend to play a more limited role in major conflicts than land-based aircraft do.)

Past and Planned Use. The United States has frequently 

used amphibious ships to deploy Marine Corps forces for 

small-scale operations, and it seems likely to continue to 

do so in the future. The United States has also deployed 

amphibious ships for major combat operations, but it has 

not conducted any large-scale amphibious assaults since 

the 1950 Inchon landings during the Korean War. 

Amphibious ships played a fairly minor role in the 1991 

and 2003 wars with Iraq.25 However, during operations 

against the Taliban in 2002, a small Marine Corps force 

assaulted Kandahar, Afghanistan, from an amphibious 

ready group more than 400 miles away in the Indian 

Ocean. That assault showed the ability of modern 

amphibious forces to deploy entirely by air over a 

long range. (For a discussion of those and other past 

military operations, see Appendix C.)

For some time, the Navy and Marine Corps have maintained a goal of having enough amphibious ships to 

deploy the assault echelons of two Marine expeditionary 

brigades (MEBs) in an amphibious assault. That goal is 

somewhat nebulous because MEBs are not standardized 

units, but transporting two of them would probably 

require about 15 amphibious ships. Ensuring that 15 

amphibious ships were at sea when needed would in turn 

require 30 amphibious ships to be operationally available 

at a given time, out of the Navy’s stated inventory goal of 

34 ships. 

The main challenge of such an amphibious assault would 

be to assemble enough ships at sea at the same time and 

place—a challenge that would depend primarily on the 

Navy’s ability to rotate and schedule ships efficiently. 

(Deploying all of the Navy’s ships simultaneously is 

impossible because, at any one time, much of the fleet is 

at its home port undergoing maintenance, being used for 

training, or in transit to or from its area of operations.) 

The Navy and Marine Corps would prefer to have a total 

fleet of 38 amphibious ships. However, that goal appears 

unlikely to be met at any time in the foreseeable future 

because the Navy’s acquisition plans do not envision constructing that many amphibious ships.26

The Marine Corps has not conducted a MEB-size 

amphibious assault in many decades, and few of DoD’s 

planning scenarios combine all of the factors necessary to 

make a MEB-size or larger amphibious assault a desirable 

option. That subject is discussed in more detail later in 

this chapter, in the special-topic entry on forcible-entry 

operations. 

Like other surface ships, amphibious ships are used extensively during peacetime for routine patrols to provide forward presence. Their notional operating cycle—one 

7-month deployment every 36 months—means that with 

the current fleet of 33 amphibious ships (4 of which are 

based in Japan), the Navy can have the equivalent of 

8 amphibious ships providing overseas presence yearround and a 9th ship for about 4 months of the year. 

Acquiring more amphibious ships, lengthening deployments, or basing more amphibious ships overseas would 

increase the fleet’s capacity to provide forward presence, 

whereas having fewer ships, shortening deployments, or 

withdrawing ships based in Japan would decrease that 

capacity. In recent years, high demand for operating 

amphibious ships overseas has led the Navy to extend 

deployments for most amphibious ships well beyond the 

7 months of their official operating cycle (which is itself 

an increase from 6 months a decade ago). 

25. In 1991, Marine Corps forces onboard amphibious ships were 

credited with playing a diversionary role, possibly forcing the Iraqi 

military to defend the coastline with forces that would otherwise 

have been committed to defending Kuwait’s land borders.

26. For a detailed discussion of the Navy’s shipbuilding plans, see 

Congressional Budget Office, An Analysis of the Navy’s Fiscal 

Year 2016 Shipbuilding Plan (October 2015), www.cbo.gov/

publication/50926.
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Major Element of the Force Structure

Marine Corps Infantry Battalions

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

The Marine Corps’ infantry battalions, unlike the Army’s 

brigade combat teams (BCTs), are “pure” light-infantry 

organizations that are not intended to operate independently. Instead, they are assembled into task forces—tailored to the needs of a specific operation—with other 

ground combat forces, air-support and logistics units, 

and a headquarters element for the whole task force. A 

Marine expeditionary unit (MEU) is a task force based 

on an infantry battalion (see Figure 3-2 on page 62), and 

a Marine expeditionary brigade (MEB) is a task force 

based on a regiment (typically with three battalions). The 

largest organization in the Marine Corps is based on an 

infantry division (which usually consists of three regiments) and is referred to as a Marine expeditionary force 

(MEF). 

The Marine Corps maintains three MEFs as standing 

peacetime organizations, but it assembles MEUs and 

MEBs only as needed for actual operations.27 The Marine 

Corps also tailors its MEFs for some deployments. For 

example, when I Marine Expeditionary Force deployed to 

Kuwait in 1991 and to Iraq in 2003, it did not include 

exactly the same set of units that it normally includes 

when stationed at Camp Pendleton in California.

Although Marine task forces other than MEFs are not 

standardized units, the Congressional Budget Office’s 

modeling approach of allocating support units to major 

combat units produces an estimated size and cost for a 

Marine infantry battalion that approximates an “average” 

for Marine Corps ground combat and air combat forces 

and their associated support units. Under that approach, 

if a notional Marine Corps task force consisted of three 

battalions (three MEUs or a single MEB), it would have 

three times the number of personnel, and three times the 

cost, of the average battalion-size force discussed here.28

In CBO’s analysis, a fully supported Marine infantry battalion is assigned a proportional share of the following: 

B Each Marine division’s assets, which include field artillery regiments, tank battalions, light armored vehicle 

battalions, and amphibious assault battalions;

Military Personnel per Unit 5,780 1,490 1,990 2,300

Annual Cost per Unit 740 140 140 470

(Millions of 2017 dollars)

Military Personnel per Unit 4,370 2,070 560 1,740

Annual Cost per Unit 470 70 50 350

(Millions of 2017 dollars)

Military Personnel per Unit 2,750 760 890 1,090

Annual Cost per Unit 520 160 140 220

(Millions of 2017 dollars)

Total Direct Overhead Indirect

Active-Component Marine Infantry Battalion

Reserve-Component Marine Infantry Battalion

Marine Aircraft Complement

27. The Marine Corps maintains several headquarters for the smaller 

organizations, but those headquarters do not have units attached 

to them when they are not taking part in operations.

28. In practice, smaller Marine Corps task forces tend to be assembled 

for less demanding tasks and include fewer support personnel.
66 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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B Each Marine aircraft wing’s squadrons of aircraft, 

which consist of utility helicopters, attack helicopters, 

heavy-lift helicopters, tilt-rotor aircraft, and shorttakeoff, vertical-landing attack aircraft; and 

B Each Marine logistics group’s assets, which provide 

logistical support to Marine Corps forces. 

Although Marine Corps doctrine treats ground and air 

assets as inseparable parts of task forces, CBO separated 

the aircraft and air crew of each infantry battalion’s support units into a separate category (referred to here as an 

aircraft complement) to more clearly display their costs.29

However, for reasons discussed below in the special-topic 

entries on Navy and Marine Corps integration (page 70) 

and naval shipborne aviation (page 74), CBO did not 

include the Marine Corps’ F/A-18 fixed-wing aircraft in 

the aircraft complements. Similarly, not all of the personnel that CBO displays as associated with Marine units are 

marines—some are Navy personnel assigned to Marine 

Corps units.

Current and Planned Structure. The Marine Corps 

intends to field 24 infantry battalions in the active component and 8 infantry battalions in the Marine Corps 

Reserve in 2017, with no plans to change either number 

through 2021. Those battalions and their aircraft complements account for virtually all of the Marine Corps’ 

operation and support funding but about one-third of 

the Department of the Navy’s operation and support 

funding.

Purpose and Limitations. A fully supported MEU, 

MEB, or MEF is roughly the same size as an equivalent 

Army ground combat formation but has a different mix 

of combat and support units. At the highest level, the 

differences are mostly attributable to the Marine Corps’ 

integration of fixed-wing aircraft into its forces. The 

Army does not have its own fixed-wing attack aircraft and 

relies more heavily on its field artillery units for fire support, whereas the Marine Corps maintains a large complement of fixed-wing attack aircraft but only a modest 

amount of field artillery. Another difference is that 

Marine Corps units generally include more direct combat 

units—with a relatively large amount of infantry in each 

battalion and a variety of armored vehicles, such as tanks 

and personnel carriers—as well as robust support from 

rotary-wing aircraft. At the same time, Marine Corps 

units have a more limited variety of supporting units, 

such as air-defense capability, and a more limited logistics 

structure (in part because the Army is responsible for 

theater-level logistics functions). 

Such structural differences may not be as operationally 

significant as they appear, however, because U.S. forces 

always operate as joint (multiservice) forces. Army BCTs, 

for example, receive substantial air support from the Air 

Force’s fixed-wing aircraft, and they are not necessarily 

deficient compared with Marine Corps regiments merely 

because that fixed-wing air support is not part of a BCT.

The main limitation of Marine Corps battalions is that, 

being primarily a light-infantry force with a limited 

armored component, they are not well suited for combat 

against heavily armored opponents in unfavorable terrain. 

However, that limitation may be less significant in practice than it is for the Army’s infantry BCTs, because 

Marine Corps forces have access to some armored vehicles (each Marine division includes a tank battalion, for 

example) and also have access to a wider array of airsupport assets (in the form of Marine Corps fixed-wing 

aircraft) that are organic to (included in) the force. 

One criticism sometimes leveled at Marine Corps battalions is that when they are not performing amphibious 

assault missions, they essentially form a second Army, 

which is duplicative and wasteful for the United States. 

The U.S. military’s practice of maintaining two separate 

armed services to provide ground combat forces is 

unusual compared with what most other nations do. 

However, the Marine Corps has a long record of combat 

on land in operations unconnected to its amphibious 

assault mission, and DoD often employs Marine Corps 

ground forces as if they are essentially interchangeable 

with Army ground forces. Moreover, Marine Corps and 

Army units routinely operate together as part of joint 

forces. In theory, the United States might gain some 

benefits from consolidating ground combat forces in a 

single military service. But in practice, it is difficult to 

identify any substantial inefficiencies at the Department 

of Defense that result from maintaining large Marine 

Corps ground combat units.

29. In CBO’s analysis of the Marine Corps’ forces, the direct costs and 

personnel of an infantry battalion or aircraft complement represent those of the ground combat or air combat elements, whereas 

the indirect costs and personnel represent those of the command 

and logistics elements.
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Some observers argue that the two ground services have a 

complementary relationship rather than a duplicative 

one. In that view, the Marine Corps’ strengths in being 

able to deploy forces from the sea and in integrating 

fixed-wing aircraft with ground units complement the 

Army’s strengths in conducting large-scale combat operations (involving infantry, armored units, and other types 

of forces) and in coordinating combat logistics. 

Past and Planned Use. Marine Corps ground forces have 

taken part in all of the United States’ major combat operations in recent history—including Operation Desert 

Storm (to remove Iraqi forces from Kuwait in 1991), 

Operation Iraqi Freedom (the invasion of Iraq in 2003), 

and Operation Enduring Freedom (the invasion of 

Afghanistan in 2001)—as well as in numerous smaller 

operations. In Operations Desert Storm and Iraqi Freedom, DoD successfully used Marine Corps forces against 

an Iraqi army that had large numbers of armored vehicles 

in desert terrain (which is generally considered highly 

advantageous to armored forces).30 In addition, Marine 

Corps ground forces were heavily involved in subsequent 

counterinsurgency operations in Iraq and Afghanistan. 

(For a discussion of those and other past military operations, see Appendix C.)

In the 1990s, DoD’s post–Cold War planning focused on 

being able to fight two major wars simultaneously (or 

nearly simultaneously). Each war was generally assumed 

to require four Marine regiments (of three battalions 

each). Subsequent planning has not been as rigid but 

envisions needing similar numbers of Marine Corps units 

for major conflicts, which means that the eight regiments 

in the Marine Corps’ active component and three in the 

Marine Corps Reserve would be enough for two major 

conflicts. However, if the future security environment is 

dominated by scenarios that place more emphasis on 

naval and air forces—such as potential operations around 

Taiwan, the South China Sea, or the Strait of Hormuz—

the need for ground forces may decline (see Appendix C).

In principle, the need for Marine Corps infantry battalions is affected by the number of three-ship amphibious 

ready groups (ARGs) that the Navy maintains. However, 

the Marine Corps is significantly larger than necessary to 

satisfy the demand for MEUs on ARGs. With 2 or 3 ARGs 

typically at sea at any time (each with a MEU), the Marine 

Corps would have to use only 6 to 9 of its 24 activecomponent infantry battalions to meet that need (given 

the common ratio of 2 nondeployed units needed to sustain 1 deployed unit). Very large reductions in the size 

of the Marine Corps, without a similar reduction in the 

size of the amphibious force, might imperil the Marine 

Corps’ ability to provide MEUs for ARGs, but small or 

moderate changes to the size of the Marine Corps would 

not—assuming that the Marine Corps was not under 

heavy pressure from other commitments. At times when 

the service has had other major commitments, such as 

providing ground forces during the occupation of Iraq, 

keeping a large enough pool of forces to provide MEUs 

for ARGs was demanding, requiring DoD to set priorities 

for its limited number of assets.

30. In Operation Desert Storm, Army heavy forces were primarily 

responsible for attacking and destroying Iraqi Republican Guard 

divisions (Iraq’s most capable armored units), while Marine Corps 

ground forces were responsible for liberating Kuwait. In Operation Iraqi Freedom, when Iraqi forces were less well equipped and 

capable, Army and Marine Corps ground forces each had their 

own attack paths.
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Major Element of the Force Structure

Other Department of the Navy Units and Activities

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. Notional squadrons of 12 aircraft (actual squadrons vary in size).

b. In the analytic framework used for this report, other units and activities are generally considered to not have any units supporting them and thus to not 

have any indirect personnel or costs.

Military Personnel per Unit 660 320 80 260

Annual Cost per Unit 170 70 40 50

(Millions of 2017 dollars)

Military Personnel per Unit 1,890 630 500 750

Annual Cost per Unit 330 110 70 150

(Millions of 2017 dollars)

Total Military Personnel 14,200 8,550 0 b 5,650

Total Annual Cost 1,860 720 0 b 1,150

(Millions of 2017 dollars)

Total Military Personnel 16,440 9,900 0 b 6,550

Total Annual Cost 2,370 1,050 0 b 1,330

(Millions of 2017 dollars)

Total Military Personnel 3,530 2,130 0 b 1,410

Total Annual Cost 490 210 0 b 280

(Millions of 2017 dollars)

Total Military Personnel 37,990 22,860 0 b 15,120

Total Annual Cost 6,550 3,490 0 b 3,060

(Millions of 2017 dollars)

Total Military Personnel 770 460 0 b 310

Total Annual Cost 230 160 0 b 60

(Millions of 2017 dollars)

Total Direct Overhead Indirect

Rest of the Navy 

Rest of the Marine Corps 

Ballistic and Guided Missile Submarines

P-3 and P-8 Maritime Patrol Aircraft Squadronsa

Seabee Construction Engineers

Navy Special-Operations Forces

Marine Corps Special-Operations Forces
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Although the vast majority of the Navy’s and Marine 

Corps’ units are connected with ships and Marine expeditionary forces (MEFs), the Department of the Navy 

includes a number of other units that are not directly 

related to ships and MEFs. Together, those units account 

for 16 percent of the department’s operation and support.

The Navy’s 14 ballistic missile submarines (all from the 

Ohio class) are similar to other naval vessels in most 

respects. However, they carry nuclear weapons and are 

the Navy’s contribution to the U.S. nuclear deterrent, so 

their number is normally determined by national nuclear 

policy and by the outcomes of arms control negotiations 

rather than by the considerations that affect other U.S. 

military units.31 In its budget documents, the Navy combines ballistic missile submarines and guided missile 

submarines, which are 4 former ballistic missile submarines that have been converted to launch Tomahawk 

cruise missiles and to support special operations. Those 

guided missile submarines are less subject to arms control 

considerations than the ballistic missile submarines are.

The Navy’s fleet of approximately 90 maritime patrol 

aircraft consists of land-based, long-range aircraft 

equipped with a variety of sensors and weapons. They are 

capable of monitoring large areas of the ocean, improving 

the Navy’s ability to find and track other nations’ ships 

and submarines. They are also capable of conducting limited attacks on ships and submarines. The older P-3 

model patrol aircraft are currently being replaced by 

newer P-8 model aircraft. The Navy is also in the process 

of fielding an unmanned long-range patrol aircraft, the 

MQ-4 Triton, which is based on the airframe of the Air 

Force’s RQ-4 Global Hawk (discussed in Chapter 4).

The Navy’s construction engineers, referred to as 

Seabees, provide a variety of engineering services to the 

Navy. They have the ability to build or improve bases in 

theaters where the infrastructure and basing options are 

poor. In that role, Seabees have contributed greatly to the 

success of past U.S. military operations in distant theaters. Because the United States has often intervened in 

countries with poor infrastructure—and because deploying U.S. forces can place great strain on the ports and air 

bases that receive them—the capability to improve that 

infrastructure has typically been highly valuable, although 

less recognized than some of the service’s other capabilities. Unlike most of the Navy’s forces, a relatively large 

percentage of Seabees are in the Naval Reserve.

The Navy and Marine Corps also maintain specialoperations forces, which are trained, equipped, and 

overseen by the Department of Defense’s Special Operations Command (SOCOM). They focus on such missions as unconventional warfare, special reconnaissance, 

counterterrorism, or the training of foreign militaries. 

The forces overseen by SOCOM are discussed in more 

detail in Chapter 5, which deals with defensewide 

activities.

By the Congressional Budget Office’s estimate, about 

38,000 military personnel and $6.5 billion a year are 

devoted to units and activities of the Department of 

the Navy other than those described in this chapter.

They consist of a variety of smaller organizations providing specialized capabilities; examples include the Navy’s 

and Marine Corps’ contributions to various joint commands and defensewide organizations, as well as some 

miscellaneous command-and-control functions. 

31. Arms control agreements can affect not only the number of ballistic missile submarines in the fleet but also the number of Trident 

missiles that each submarine carries and the number of warheads 

on each Trident missile. Ballistic missile submarines are generally 

considered to be the best available element of U.S. nuclear forces 

for ensuring that the nation maintains a “second-strike” nuclear 

capability—that is, it would be extremely difficult for an enemy 

to destroy ballistic missile submarines that were at sea, so those 

submarines would most likely be available to retaliate against any 

nuclear attack.
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Special Topic

Integration of the Navy and Marine Corps 

Amphibious operations offer perhaps the most iconic 

image of the close relationship between the Navy and 

the Marine Corps, with Navy ships carrying Marine 

Corps units into battle. However, the two “sea services” 

are integrated on a much deeper level than that in their 

day-to-day operations.

This report follows conventional usage in talking about 

Navy ships and Marine Corps combat units, but in reality, many Navy ships have Marine Corps personnel 

onboard as part of their crew (although that practice is 

becoming less widespread than it used to be).32 In some 

cases, larger Marine Corps units—such as entire squadrons of aircraft within carrier air wings—provide a significant share of a ship’s combat power. Similarly, Marine 

Corps units include some Navy personnel; for example, 

all medical personnel assigned to Marine Corps units are 

members of the Navy. Thus, nearly all large Navy and 

Marine Corps units are actually a mix of personnel from 

both services.

For the purposes of this analysis, the extent to which the 

support and administrative structures of the Navy and 

Marine Corps are intertwined makes it impossible to 

determine which of the costs and personnel dedicated 

to sustaining the Department of the Navy’s (DoN’s) combat units should be allocated to the Navy and which to 

the Marine Corps. Such intertwining is pervasive. For 

example, the U.S. Naval Academy produces officers for 

both the Navy and Marine Corps, and the training establishments for weapon systems that both services operate, 

such as F/A-18 aircraft, are largely integrated as a single 

establishment within DoN. For those reasons, this analysis focuses on the department rather than on each of its 

services individually.

Functions that are performed by civilians are performed 

by DoN civilians—there are no Navy or Marine Corps 

civilians (although DoN personnel can be assigned to 

Navy or Marine Corps organizations). DoN organizations staffed by DoN civilians are responsible for many 

administrative duties that support both services, such as 

management of the Navy’s and Marine Corps’ budgets. 

For weapon systems used by both services, DoN generally 

integrates functions such as procurement and depot 

maintenance.33

The strong interrelationship between the Navy and the 

Marine Corps is based on tradition: The need to provide 

soldiers onboard ships was the original reason for the 

existence of a Marine Corps. That tight interweaving is 

usually described as having a variety of positive effects. 

The most prominent effect is that it helps to produce a 

common culture in the two sea services that promotes 

trust and cooperation. Such close integration is also seen 

as a natural extension of the expeditionary nature common to the two services—the routine, frequent peacetime 

deployments that both services are accustomed to conducting are distinct from the more limited peacetime 

deployments traditionally practiced by the Army and the 

Air Force. Another natural complement between the sea 

services is that the Navy’s greatest limitation as a combat 

force is its limited ability to project power ashore, and the 

Marine Corps provides that ability to the Navy. Similarly, 

the Navy provides the means to convey Marine units to 

operations.

The benefits of the Navy and Marine Corps’ integration 

are sometimes contrasted (by implication if not explicitly) 

with the historical relationship between the Army and the 

Air Force. Since 1947, when the Air Force was created by 

splitting off the Army Air Corps from the Army, the Air 

Force has made a great effort to differentiate itself from 

the Army as a separate and distinct service, with separate 

and distinct missions, culture, weapon systems, and warfighting doctrine. At times, those separate cultures have 

32. Historically, shipboard detachments of marines were used for 

several purposes, such as deterring potential mutineers; allowing 

ships to make small landings; repelling or initiating boarding 

actions; and, during the Cold War, guarding nuclear weapons. 

Providing shipboard detachments was the primary function of the 

Marine Corps during the 18th and 19th centuries, but that function declined in importance during the 20th century. Today, the 

use of shipboard detachments is greatly reduced, in part because of 

the need for marines in the ground combat operations in Iraq and 

Afghanistan.

33. For example, all of DoN’s aircraft are purchased through the Aircraft Procurement, Navy, appropriation. Separating that appropriation into “blue” (Navy) and “green” (Marine Corps) funding—as 

some analysts do when trying to describe each service’s spending 

independently—requires detailed knowledge of specific programs, 

multiple assumptions, and significant analytic effort.
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led the Air Force and the Army to disagree in important 

ways about military operations, particularly about the Air 

Force’s provision of close air support to Army ground 

combat units.34 Some observers (and Army personnel) 

have argued that the Air Force is reluctant to provide as 

much close air support as Army ground combat units 

need, preferring to wage separate air campaigns largely 

disconnected from ground combat operations. However, 

other observers say that such differences are overstated 

and that the Air Force has always supported Army units 

during combat operations (regardless of their specific 

views about the nature of joint operations and the role 

of airpower at the time). Compared with those two services, the Navy and Marine Corps appear to coordinate 

operations more smoothly and be less inclined to try to 

conduct operations separately.

34. “Close air support” generally refers to attacks by combat aircraft 

on enemy forces that are in contact with U.S. ground forces (often 

conducted at the request of those ground forces)—as opposed to 

air attacks on fixed installations, enemy forces not in contact with 

U.S. ground forces, or other targets.
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Special Topic

Forcible-Entry Capability

Forcible entry occurs when a military force gains access to 

enemy territory that cannot be reached from adjacent 

land areas. Three main types of forcible-entry operations 

exist, each performed by specialized forces:

B Airborne assault, in which troops parachute into an 

area from fixed-wing aircraft;

B Air assault, in which troops attack from helicopters; 

and

B Amphibious assault, in which troops are carried to 

shore on naval landing craft.

Unlike conventional ground operations, in which troops 

advance from friendly terrain into adjacent enemy terrain, forcible-entry operations focus on giving troops 

access to enemy territory that is behind the enemy’s lines, 

far from friendly territory, on hostile islands, or otherwise 

not accessible to conventional ground forces.

History and Nature of Forcible-Entry Operations. 

The value of forcible-entry capability was demonstrated 

in many dramatic ways in World War II. Amphibious 

assaults were central to the conduct of the war in the 

Pacific, where the United States fought Japan across a 

string of island chains and archipelagos and made plans 

to assault the island nation of Japan. In the European 

theater, the lack of any Allied-controlled territory on the 

mainland of Western Europe made amphibious assaults 

into North Africa, Sicily, mainland Italy, and the French 

province of Normandy crucial to the overall goal of 

invading and defeating Germany. Forcible-entry operations by air were not feasible in the Pacific because of the 

great distances between islands, but the European theater 

saw several major airborne assaults (in conjunction with 

amphibious assaults in Sicily and Normandy). During 

the Korean War, a major amphibious assault at Inchon 

demonstrated the power of forcible-entry operations to 

change the course of a conflict.

Helicopters were not developed enough during earlier wars 

to perform air-assault operations, but in the Vietnam War, 

the Army employed air-assault tactics frequently. Air 

assaults were generally used to rapidly bring large concentrations of Army forces into contact with Viet Cong and 

North Vietnamese Army units, which often preferred to 

avoid direct confrontation with U.S. troops. Since then, 

the Army’s air-assault forces have relied on helicopters for 

mobility in most conflicts in which those forces have 

been used. The Marine Corps’ amphibious forces also 

include an air-assault component of helicopters and tiltrotor aircraft. In an amphibious operation, the air assault 

would most likely be conducted in coordination with an 

assault by Marine forces in Navy landing craft.

The brigade combat teams (BCTs) of the Army’s 82nd 

Airborne Division and the Air Force’s fleet of large cargo 

aircraft are the main elements of the U.S. force structure 

necessary for airborne assaults. The BCTs of the Army’s 

101st Airborne Division and the Army’s cargo and utility 

helicopters are the main elements necessary for air assaults. 

And the Marine Corps’ ground forces, helicopters, and 

landing craft, along with the Navy’s amphibious ships 

and landing craft, are the main elements of the force 

structure needed for amphibious assaults. In addition, 

U.S. special forces have conducted all three types of 

forcible-entry operations on many occasions—though on 

a much smaller scale—to gain access to hostile territory.

Under certain circumstances, the U.S. military has combined elements of its forcible-entry capability in other 

ways. For example, during the war in land-locked 

Afghanistan, Marine Corps forces conducted an air 

assault on the city of Kandahar from amphibious ships 

more than 600 miles away in the Indian Ocean. And 

when the United States prepared to invade Haiti in support of an ousted president in the mid-1990s, the military planned to conduct the invasion using Army airassault forces (infantry and helicopters) transported on 

Navy aircraft carriers. More recently, the Department 

of Defense has explored the concept of “sea basing,” in 

which Navy ships would serve as the rear area of a theater 

during a conflict—performing all logistics functions for 

a force on shore—and would be connected to ground 

forces in combat by a “bridge” of aircraft and landing 

craft.35

35. See Congressional Budget Office, Sea Basing and Alternatives for 

Deploying and Sustaining Ground Combat Forces (July 2007), 

www.cbo.gov/publication/18801. 
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Advantages and Disadvantages of Forcible-Entry 

Operations. The major advantage of forcible-entry operations is that, under some circumstances, it is impossible 

to fight an adversary without them. Enemy-held islands, 

or other territories that do not have a land border with a 

friendly state, are inaccessible to conventional ground 

operations. In addition, forcible-entry capabilities can 

be important for gaining major combat advantages 

through surprise and mobility (as in the Inchon landing). 

Scenarios in which such capabilities could be useful in the 

future include possible operations in North Korea or the 

Strait of Hormuz (for a description of such scenarios, see 

Appendix C). On a smaller scale, the use of helicopters 

for air-assault operations has allowed U.S. forces to operate relatively freely in the mountainous landscape of 

Afghanistan, avoiding some of the limitations that the 

country’s poor infrastructure and rugged terrain would 

otherwise impose.

One of the main drawbacks of forcible-entry operations is 

that, if conducted in the face of strong opposition, they 

can be extremely dangerous, and if unsuccessful, they 

have the potential to result in heavy losses. During World 

War I, the troops taking part in Britain’s amphibious 

assault at Gallipoli were unable to penetrate inland, and 

they suffered enormous casualties from combat and illness before their beachhead was evacuated. In World War 

II, Britain’s 1st Airborne Division suffered a casualty rate 

of about 80 percent during Operation Market Garden, an 

unsuccessful airborne assault intended to penetrate German lines as part of the Allies’ invasion of Germany. And 

in 1980, an air assault intended to rescue Americans held 

hostage in Iran was aborted well before reaching its target 

after most of the helicopters committed to the mission 

were lost because of mechanical failure or accidents. 

Even when forcible-entry operations succeed in taking 

the intended enemy territory, their difficulty can be so 

great as to outweigh the benefits. For instance, when U.S. 

forces invaded the Pacific island of Peleliu during World 

War II, they were unprepared for the intensity of Japanese 

resistance and suffered numerous casualties, far in excess 

of the island’s strategic value.36 Also during that war, 

Allied forces that staged an amphibious assault at Anzio, 

Italy, were isolated in a small pocket near their beachhead 

for a long period, unable to break out, and were largely 

irrelevant to the battle for Italy.37

To be feasible, forcible-entry operations require a number 

of preconditions to be met. Airborne- and air-assault 

operations require control of local airspace, and amphibious operations require control of local airspace and local 

waters. Surprise is necessary to reduce risk, and major 

operations must occur either close enough to friendly 

ground forces to allow them to link up or close enough to 

a port to allow follow-on forces to be deployed. (In some 

more limited operations, capturing an airfield may be sufficient to allow follow-on forces to be deployed.)

The majority of units and equipment associated with the 

United States’ forcible-entry capability have the ability to 

perform other roles as well. Apart from some additional 

training and equipment, the Army’s air-assault and airborne BCTs are almost identical to other Army light 

BCTs, and they are routinely used interchangeably with 

other light BCTs in conventional operations. Similarly, 

the Army’s cargo and utility helicopters can be used for a 

wide variety of missions besides air assaults. And the 

Marine Corps’ ground and air forces have been used 

extensively for combat in conventional operations. In 

most respects, the only significant additional units and 

equipment (and thus cost) involved in maintaining 

forcible-entry capabilities is the Navy’s fleet of amphibious ships and specialized landing craft. (The Marine 

Corps’ landing craft are not designed exclusively for 

amphibious assaults; they also serve as armored personnel 

carriers for Marine ground forces operating on shore, 

although they are less useful in that role than conventional personnel carriers.)

36. See Center for Military History, Western Pacific, 15 June 1944–

2 September 1945 (October 2003), www.history.army.mil/

brochures/westpac/westpac.htm.

37. See Center for Military History, Anzio, 22 January–24 May 1944

(January 2010), www.history.army.mil/brochures/anzio/

72-19.htm.
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Special Topic

Naval Shipborne Aviation

Naval shipborne aviation consists of the squadrons that 

make up carrier air wings and the shipboard helicopters 

on surface combatants. Carrier air wings are composite 

units with several types of aircraft; their per-unit costs 

and personnel were presented in an entry, “Aircraft Carriers,” on page 52. Likewise, the costs and personnel for 

shipboard helicopters on surface combatants were shown 

in an entry, “Surface Combatants,” on page 56. In this section, the Congressional Budget Office breaks out the personnel and costs for those same Navy aircraft by the type of 

aircraft—rather than by the type of ship they are associated 

with—and describes the roles that each kind of aircraft 

plays.

All units presented under this topic are notional squadrons of 12 aircraft (actual squadrons vary in size).

In all of the tables under this topic, “direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated 

with units that support the major combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or 

overhead activities. The numbers shown in these tables are rounded to the nearest 10 personnel or $10 million. 

F/A-18s are multirole fixed-wing aircraft capable of 

attacking other planes in the air or targets on the ground. 

Two varieties are currently in use: the older C/D model 

and the newer E/F model that is based on it. The F/A18E/Fs are significantly larger and more capable than 

their predecessors, with a longer range, greater payload 

capacity, and improvements to their electronics and other 

systems. The fleet of F/A-18s is the mainstay of naval 

shipborne aviation, providing the vast majority of the 

Navy’s ability to strike targets. (Most other naval aircraft 

are used for support purposes, as described below.) The 

Marine Corps also operates F/A-18s. Some are used 

aboard aircraft carriers as integral parts of a carrier air 

wing; others are used to support Marine Corps operations 

from air bases on land. The Navy and Marine Corps plan 

to field 542 F/A-18s in 2017; that inventory is scheduled 

to decline to 522 in 2021 as F-35 aircraft begin to replace 

older F/A-18s.

EA-18G aircraft are a variant of the F/A-18F, specialized 

for jamming an enemy’s transmissions (electronic warfare) and for attacking an enemy’s air defenses.(They 

have largely replaced the Navy’s older fleet of EA-6B aircraft, which performed the same roles.) In the 1990s, 

with the retirement of the Air Force’s fleet of EF-111s, 

the Department of Defense decided to make the Navy 

responsible for providing all electronic warfare support to 

U.S. forces. Thus, EA-18Gs support operations not only 

by aircraft carriers and Marine Corps units but also by 

the Air Force. The Navy plans to field an average of 

96 EA-18Gs over the 2017–2021 period.

Military Personnel per Unit 780 260 210 310

Annual Cost per Unit 160 60 40 60

(Millions of 2017 dollars)

 Total Direct Overhead Indirect

F/A-18 Fighter/Attack Aircraft Squadron

Military Personnel per Unit 1,420 480 380 570

Annual Cost per Unit 240 80 50 110

(Millions of 2017 dollars)

Total Direct Indirect Overhead

EA-18G Electronic Attack Aircraft Squadron
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Because F-35s are not yet in full operational service, their actual costs may differ from the planned costs included in the Department of Defense’s budget 

documents, on which these estimates are based.

The Department of the Navy is acquiring a new fighter 

aircraft, the F-35, also known as the Joint Strike Fighter. 

It is being produced in two variants for the department: 

The B version will offer short-takeoff, vertical-landing 

capability to the Marine Corps (that capability is discussed in more detail in the special-topic entry on Marine 

Corps aviation below), and the C version will be capable 

of taking off from and landing on aircraft carriers. The 

F-35Cs will replace the Navy’s current F/A-18C/Ds, 

performing the same missions. Although they are 

expected to be superior to those F/A-18C/Ds in many 

ways, the largest improvement they will offer is providing 

the Navy with a low-observable (or “stealthy”) attack aircraft. The Navy and Marine Corps plan to field 97 F-35s 

by 2021, replacing older F/A-18s.

The Navy uses H-60 helicopters for a variety of purposes, 

such as moving passengers, supplies, and small loads of 

cargo. Their combat roles include antisubmarine warfare 

and anti–surface warfare. Helicopters are very well suited 

to antisubmarine warfare because they can move rapidly 

to several locations and deploy cheap, disposable, floating 

sonar sensors. (Determining the position of an enemy 

submarine requires triangulation, so relying on multiple 

sonars in the water is generally more effective than using a 

single shipboard sonar.) Navy surface combatants usually 

have one or two SH-60 helicopters (antisubmarine variants of the H-60) onboard, and aircraft carriers have a 

squadron of up to eight helicopters. Although they have 

traditionally been specialized for antisubmarine warfare, 

some models of the H-60 can be equipped with anti–

surface-ship weapons, such as Hellfire missiles. In that 

configuration, helicopters are useful for operations 

against small boats, such as antipiracy missions. The 

Navy plans to field 236 H-60 helicopters throughout the 

2017–2021 period.

Military Personnel per Unit 260 90 70 100

Annual Cost per Unit 150 80 50 20

(Millions of 2017 dollars)

 Total Direct Indirect Overhead

F-35 Fighter Aircraft Squadron

Military Personnel per Unit 1,000 330 270 400

Annual Cost per Unit 170 50 30 80

(Millions of 2017 dollars)

 Total Direct Indirect Overhead

H-60 Helicopter Squadron
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C-2s and E-2s are specialized aircraft that support the 

operations of aircraft carriers. C-2s are small transport 

planes used to bring supplies and personnel to and from 

an aircraft carrier while it is under way. E-2s are variants 

of the C-2 that are specialized to serve as platforms for 

airborne radar; such radar greatly improves the ability of a 

carrier strike group to detect and engage aerial and surface targets. In using radar to detect targets at long range, 

ships (or other platforms on the surface) are intrinsically 

limited by the curvature of the Earth. (Radar, like visible 

light, has a horizon below which any target cannot be 

seen.) By flying high, aircraft can increase the range at 

which they can detect targets. For the same reason, the 

Air Force uses E-3 surveillance aircraft for its operations. 

The Navy plans to continue to field 25 C-2 and 45 E-2 

aircraft through 2021.

Military Personnel per Unit 1,140 380 300 450

Annual Cost per Unit 190 60 40 90

(Millions of 2017 dollars)

Military Personnel per Unit 1,240 410 330 490

Annual Cost per Unit 230 80 50 100

(Millions of 2017 dollars)

Overhead

E-2 Surveillance Aircraft Squadron

Total Direct Indirect

C-2 Transport Aircraft Squadron
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Special Topic

Marine Corps Aviation

The Marine Corps’ aviation units are organized into 

squadrons that make up Marine aircraft wings. Those air 

wings are composite units with several types of aircraft. 

Their per-unit costs and personnel are presented in the 

entry about Marine Corps infantry battalions on page 65 

as the aircraft complement to a battalion. In this section, 

the Congressional Budget Office breaks out the personnel 

and costs for those same Marine Corps aircraft by type 

of aircraft and describes the roles that each type of aircraft 

performs. The discussion excludes the Marine Corps’ 

F/A-18 fighter/attack aircraft, which are discussed in the 

special-topic entry about naval shipborne aviation on 

page 74.

All units presented under this topic are notional squadrons of 12 aircraft (actual squadrons vary in size).

In all of the tables under this topic, “direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated 

with units that support the major combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or 

overhead activities. The numbers shown in these tables are rounded to the nearest 10 personnel or $10 million. 

AV-8Bs are fixed-wing aircraft with short-takeoff, 

vertical-landing (STOVL) capability that are intended 

mainly to attack targets on the ground. Unlike conventional fixed-wing aircraft, they do not need long runways 

at an air base to take off or arrestor hooks on an aircraft 

carrier to land. Instead, they can perform a rolling takeoff 

from a short runway and can land vertically, like a helicopter. Those qualities allow AV-8Bs to be based in locations with limited infrastructure for aircraft or to be based 

on LHA- or LHD-type amphibious ships (which have 

much smaller flight decks than aircraft carriers and no 

catapults or arresting wires). However, those capabilities 

also necessitate a very specialized form of aircraft design, 

which requires design compromises that make STOVL 

aircraft less capable in certain respects—especially range 

and payload capacity—than other fixed-wing aircraft of 

similar size. 

The Marine Corps intends to replace its current fleet of 

AV-8Bs with the F-35B variant of the Joint Strike Fighter, 

which will have a similar STOVL capability (and similar 

limitations compared with other versions of the F-35). 

The Marine Corps’ use of STOVL aircraft has long been 

the subject of criticism. One reason is that most Marine 

air operations are conducted from land bases that do 

not require STOVL capability. Another reason is that 

STOVL aircraft are costly to design, expensive to order in 

the relatively small quantities that the Marine Corps uses, 

and less capable in many ways than equivalent aircraft 

with conventional landing capabilities. The Marine 

Corps accepts those trade-offs to obtain fixed-wing air 

support that it can operate from amphibious ships or 

from small bases on shore. The Marine Corps plans to 

field 80 AV-8Bs in 2017; that inventory is scheduled 

to decline to 48 in 2021 as F-35 aircraft begin to replace 

AV-8Bs.

Military Personnel per Unit 960 250 330 380

Annual Cost per Unit 180 50 50 80

(Millions of 2017 dollars)

Total Direct Overhead Indirect

AV-8B Attack Aircraft Squadron
78 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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The H-1 series of helicopters consists of two types: 

UH-1s, utility helicopters capable of transporting small 

loads of cargo and personnel, and AH-1s, attack helicopters that provide fire support to Marine Corps ground 

forces. (Despite their different roles, the AH-1 began its 

life as a modified UH-1, and the Marine Corps often 

combines the budgets for the two types of helicopters.) 

In addition to being generally useful for all kinds of 

operations, variants of the H-1 are included in the 

Marine expeditionary units (MEUs) embarked on 

amphibious assault ships. (AH-1s, as attack helicopters, 

do not transport personnel or equipment but rather 

escort the transport aircraft and, if necessary, attack any 

hostile forces at the landing zone.) The Marine Corps 

plans to field an average of 232 H-1 helicopters during 

the 2017–2021 period.

The Marine Corps recently replaced its CH-46 mediumlift helicopters with V-22 tilt-rotor aircraft. Like H-1 

series helicopters, V-22s are included in the MEUs 

embarked on amphibious assault ships and are essential 

to the Marine Corps’ ability to transport personnel and 

equipment to specific locations. They are larger aircraft 

than UH-1 helicopters, with much greater transport 

capacity. The V-22 had a relatively long and difficult 

development cycle, but it is now operational and provides 

longer range and greater speed than the older CH-46 

helicopters. In most air assault operations, the V-22 fleet 

would carry the majority of Marine Corps personnel. The 

Marine Corps plans to field about 240 V-22 tilt-rotor 

aircraft by 2021.

The CH-53 heavy-lift helicopter is the final air component of the Marine Corps’ amphibious assault capability. 

By far the largest and most powerful transport helicopter 

that the Marine Corps possesses, the CH-53 can carry 

pieces of equipment by air that are too big for any other 

aircraft in a MEU. The Marine Corps is planning to 

replace its older CH-53 helicopters with a new CH-53K 

model, which would be capable of carrying even larger 

loads. The fleet of heavy-lift helicopters would transport 

the majority of equipment and supplies in most air 

assault operations. The Marine Corps plans to field 

136 CH-53 helicopters throughout the 2017–2021 

period.

Military Personnel per Unit 860 220 300 340

Annual Cost per Unit 130 30 30 70

(Millions of 2017 dollars)

H-1 Utility and Attack Helicopter Squadron

Total Direct Indirect Overhead

Military Personnel per Unit 760 200 260 300

Annual Cost per Unit 150 40 40 60

(Millions of 2017 dollars)

V-22 Medium-Lift Aircraft Squadron

Total Direct Indirect Overhead

Military Personnel per Unit 960 250 330 380

Annual Cost per Unit 190 60 60 80

(Millions of 2017 dollars)

CH-53 Heavy-Lift Helicopter Squadron

Total Direct Indirect Overhead
CHAPTER 3: DEPARTMENT OF THE NAVY THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 79

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KC-130 tankers are modified C-130 transport aircraft 

that are capable of refueling the Marine Corps’ fixedwing aircraft and helicopters while they are in flight, 

greatly extending the operating range of those aircraft. 

KC-130s retain many of the characteristics of the base 

C-130 airframe and can be used as transport aircraft 

when not needed for aerial refueling. They can also support ground operations in some circumstances. For example, during the initial invasion of Afghanistan, Marine 

Corps forces conducted a long-range air assault on 

Kandahar and received fuel for their ground vehicles and 

equipment from KC-130s. (In addition, the Marine 

Corps is acquiring weapons kits that can be used to turn 

KC-130s into armed attack aircraft, but that will be a secondary role not given to all KC-130s.) Unlike the majority of Navy and Marine Corps aircraft, KC-130s are too 

large to be based on aircraft carriers or amphibious ships; 

they must operate from air bases on land instead. The 

Marine Corps plans to field an average of 71 KC-130 

tankers during the 2017–2021 period.

Military Personnel per Unit 980 330 260 390

Annual Cost per Unit 160 50 30 80

(Millions of 2017 dollars)

KC-130 Transport/Tanker Aircraft Squadron

Total Direct Indirect Overhead

CBO

CHAPTER

4

Department of the Air Force

Overview

The Department of the Air Force includes the Air Force’s 

active component, the two parts of the service’s reserve 

component—the Air Force Reserve and the Air National 

Guard—and all federal civilians employed by the Air 

Force. It is the smallest of the three military departments 

in terms of both number of personnel and operation and 

support (O&S) budget.

The Air Force is responsible for the majority of the 

U.S. military’s air power. However, each of the military 

services has a substantial number of aircraft; thus, the 

Air Force’s specialty is not simply providing air power 

but providing a wide range of capabilities and types of 

aircraft. In addition, the Air Force is responsible for most 

of the U.S. military’s space assets and for the groundbased ballistic missiles that carry about one-third of the 

United States’ deployed nuclear weapons.1

The Air Force operates a fleet of aircraft of widely varying 

sizes that are designed to accomplish a broad array of missions. Types of aircraft unique to the Air Force include 

long-range bombers, large transport aircraft, and large 

tanker aircraft. (The other services operate a number of 

smaller cargo and tanker aircraft, but the Air Force’s are 

bigger and more numerous.) The Air Force also operates 

a large number of fighter and attack aircraft; aircraft that 

provide capabilities for airborne command and control, 

intelligence, reconnaissance, and surveillance (ISR), and 

electronic warfare (EW); and helicopters and tilt-rotor 

aircraft for combat rescue and special-operations missions. In addition, the Air Force operates a fleet of 

unmanned air systems (drones) that can carry equipment 

for ISR and EW missions as well as weapons to attack 

ground targets. Because the Air Force’s aircraft are 

expected to operate mainly from established air bases, 

their designs do not have to give up performance capabilities in exchange for specialized adaptations, such as 

the ones that enable the Navy’s aircraft to operate from 

aboard ships. The Air Force is also responsible for most 

of the military’s space systems that provide important 

support to the entire Department of Defense (such as 

Global Positioning System satellites).

Combat units in the Air Force are generally organized as 

squadrons of aircraft. Those squadrons vary widely in 

size—with anything from 8 to 24 aircraft being common—as well as in types of aircraft. Such variation makes 

it difficult to provide a single measure of force structure 

for the Air Force similar to an Army brigade combat 

team or a Navy carrier strike group. For consistency, the 

Congressional Budget Office focused in this analysis on 

notional squadrons of 12 aircraft each.2

 The Air Force’s 

planned numbers of aircraft and personnel equate to 

roughly 220 such squadrons during the 2017–2021 

period (see Table 4-1). The Air Force also includes support units (the vast majority of which are used to support 

combat operations by aircraft squadrons) and administrative units (almost all of which exist to create or maintain 

the service’s combat units and support units).

1. As noted in Chapter 3, the Navy’s ballistic missile submarines 

carry roughly the other two-thirds of the United States’ deployed 

nuclear weapons. Air Force bombers can also carry nuclear weapons, but because of the conventions used in arms control agreements, bombers are counted as carrying very few such weapons 

(officially, just one nuclear warhead each). Those conventions 

reflect a judgment that bombers are less dangerous in a crisis 

because they take much longer to reach their targets than ballistic 

missiles do and they can be recalled after they have been launched, 

which is not the case for ballistic missiles.

2. CBO decided to use a notional squadron of 12 aircraft as a standard measure simply to provide a normalized “apples to apples” 

way of comparing the sizes of different fleets of aircraft (and 

changes to those fleets over time). Actual counts of Air Force 

squadrons do not provide such a measure. A simple count of the 

number of official “slots” in each fleet would provide the same 

benefit analytically and is a fairly common way of describing the 

Air Force’s fleets. Had CBO used that metric, its estimates for 

the personnel and costs of each type of Air Force aircraft would 

be the same as those presented here but divided by 12 in each case.
82 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Table 4-1.

Number of Major Combat Units in the Air Force, 

2017 and 2021

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

All units presented are notional squadrons of 12 aircraft (actual squadrons 

vary in size).

In addition, the Air Force contains some smaller organizations that provide capabilities unrelated to aircraft or 

space systems. The most noteworthy include squadrons 

of Minuteman ballistic missiles, special-operations forces, 

and squadrons of construction engineers.

Distribution of Air Force Personnel

Of the nearly half a million military personnel serving in 

the Air Force as a whole, 29 percent are in support units 

and 37 percent are in combat units (see Table 4-2). 

The rest belong to units that perform various overhead 

functions, such as training and maintenance. 

More than the other services, the Air Force integrates 

the personnel from its active and reserve components 

very tightly—in many cases, it is misleading to treat the 

Air Force as composed of separate active- and reservecomponent units. Many Air Force units are “multi-compo” 

(multiple component) units, made up of personnel and 

equipment from both the active and the reserve components. In other cases, equipment assigned to one component may be operated by personnel from the other 

component. About one-third of the Air Force’s aircraft are 

assigned to the reserve component, which more closely 

resembles the Army’s practice than that of the Navy or 

Marine Corps. The Air Force’s reserve component is also 

unusual in that its pilots, unlike reservists in the other 

services, are frequently more experienced than their 

active-component counterparts.3

Such tight integration—combined with the way in which 

budget information is presented in DoD’s Future Years 

Defense Program (in which units must be classified as 

belonging to one component or the other, even when that 

is not strictly the case)—limited CBO’s ability to produce 

meaningful estimates of costs for active- or reservecomponent squadrons. Instead, the costs presented in this 

report for Air Force squadrons represent those of “average” 

squadrons, even though there may be no actual squadrons 

with those precise sizes and costs.4

Command Levels and Units

Today’s Air Force typically does not operate with formations larger than squadrons. In the past, the service relied 

more heavily on wings (groups of three squadrons, with 

24 aircraft per squadron). It also experimented with a 

larger formation, called an air expeditionary force, composed of several different types of squadrons. Currently, 

however, the Air Force generally deploys a group of 

squadrons organized for a specific mission, with higherlevel commands such as wings used to provide command 

and control for the deployed squadrons. As noted above, 

squadron sizes vary greatly, making counts of squadrons a 

somewhat misleading measure of force structure, which is 

why CBO translated all Air Force units into notional 

12-aircraft squadrons for this analysis.5

101 100

9 9

42 43

36 36

Squadrons 35 30

2017 2021

Airlift Squadrons

Air Refueling Squadrons

Unmanned Air System

Bomber Squadrons

Tactical Aviation Squadrons

3. Statistically, the most important determinant of a pilot’s proficiency is total hours spent flying during a career. Pilots in the Air 

Force’s reserve component are almost always former active-duty 

military pilots, many of whom have gone on to careers in civilian 

aviation; as a result, they have often spent more hours flying than 

active-component pilots.

4. For example, about one-quarter of the Air Force’s fleet of C-17 

cargo aircraft is assigned to the reserve component. However, 

cargo aircraft are commonly crewed by personnel from both the 

active and the reserve components, so it would not be accurate to 

treat one-quarter of C-17 squadrons as being in the reserve component and the other three-quarters as being in the active component (in actuality, about 90 percent of the personnel assigned to 

C-17 squadrons are reserve-component personnel). For that reason, CBO calculated per-unit costs for this report by estimating 

the cost of a single notional C-17 squadron rather than by estimating one cost for the C-17s assigned to the reserve component 

and another cost for the C-17s assigned to the active component. 

Although that approach almost guarantees that the estimated 

cost of a notional squadron does not reflect the cost of any actual 

squadron, if the Air Force made large cuts or additions to its forces 

that were not disproportionately targeted toward one component 

or the other, CBO’s notional cost would approximate the average 

savings or additional cost per squadron cut or added.

5. Today, larger aircraft, such as cargo lifters and bombers, are generally grouped into smaller squadrons, whereas tactical aircraft tend 

to be grouped into larger squadrons. However, squadron sizes are 

not standardized even for specific types of aircraft. For example, 

although fighter aircraft are often described as organized into 

squadrons of 24 aircraft, the Air Force actually organizes F-16s 

in squadrons of 15, 18, or 24 aircraft.
CHAPTER 4: DEPARTMENT OF THE AIR FORCE THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 83

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Table 4-2.

Average Distribution of the Department of the 

Air Force’s Military Personnel, 2017 to 2021

Number of Personnel

Source: Congressional Budget Office, using data from the Department of 

Defense’s 2017 budget request.

Numbers may not add up to totals because of rounding.

a. “Overhead” refers to administrative units as well as to personnel not 

assigned to any unit.

Support units in the Air Force have also evolved over 

time. In the past, a wing was a relatively fixed organization with a definite support structure, organized into several functional groups, such as an operations group or an 

aircraft maintenance group. Although modern wings still 

have functional support groups, those groups vary in size 

depending on the numbers and types of squadrons they 

need to support (which also differ in size and type). 

Moreover, detachments can be split off from those groups 

fairly easily to support individual squadrons when they 

deploy. Thus, in practice (if not in formal structure), the 

Air Force has shifted to using a number of smaller, more 

flexible kinds of support units that are capable of supporting individual squadrons rather than entire wings.

One reason that is cited for the decline of the wing and 

the rise of the squadron as the Air Force’s main element of 

force structure is that traditional tactical fighter wings 

were large and homogenous (generally composed of a 

single type of aircraft). As tactical aircraft became more 

expensive, more capable, and less numerous, 72-aircraft 

wings came to be seen as relatively inflexible, cumbersome 

units. Similarly, as the Air Force began conducting more 

sophisticated operations with different types of aircraft 

working together, mixed forces (a “composite wing”) 

became more useful than forces consisting of just one 

type of aircraft. In a sense, that shift has brought the Air 

Force closer to the way in which the other services handle 

aviation. For example, most of the Army’s aircraft are in 

aviation brigades that contain more than one type of helicopter; the Navy has always used composite carrier air 

wings, which include several smaller squadrons of mixed 

aircraft types; and the Marine Corps has long used 

Marine aircraft wings that are intended to be divided into 

smaller, task-organized groups for deployments.

At various times in the past decade, the Air Force has 

suggested a new form of higher-level organization: an 

air expeditionary force or, more recently, an air and space 

expeditionary task force. So far, however, those formations appear to be largely administrative conveniences 

(essentially, lists made in advance of disparate units that 

would be deployed together for an operation) intended to 

bring some predictability to the deployment of Air Force 

units. In practice, the Air Force appears to be evolving 

toward a system more like that of the Marine Corps, in 

which actual deployments involve task-organized formations drawn from standing units. Current Air Force doctrine supports creating ad hoc squadrons or wings during 

deployments. For example, a deployed force of fewer than 

700 personnel would warrant having one squadron, but if 

that force grew to exceed 700 personnel, commanders 

would be expected to form a second squadron and split 

assets and responsibilities between the two.

Like the other military services, the Air Force differentiates 

between the total number of fixed-wing aircraft it has and 

the number of official “slots” for those aircraft in its force 

structure. For instance, a squadron of 12 aircraft is 

intended to be able to operate that many aircraft at all times 

(in other words, it has 12 slots, called the primary aircraft 

authorization). But it may have more aircraft assigned to it 

(called the primary mission aircraft inventory) so the 

squadron can continue to operate at full strength even if 

some of those aircraft require extended maintenance or are 

otherwise unavailable. Similarly, the services have many 

aircraft that are not assigned to combat units—some are at 

maintenance depots, some are assigned to training squadrons, and some may be in storage to serve as replacements 

if aircraft are lost in the future. For those reasons, a service’s 

total aircraft inventory is greater than its primary aircraft 

authorization levels. (For example, the United States purchased 21 B-2 bombers but maintains 16 slots for B-2s in 

the force structure.) In this report, all aircraft numbers 

represent primary aircraft authorizations.

Strengths and Limitations of U.S. Air Forces

Each type of aircraft has its own strengths and weaknesses, but overall, Air Force squadrons are exceptionally 

powerful units. Very few other countries’ air forces have 

sufficient combat power to consider challenging U.S. 

control of the air; in many of the conflicts that the United 

Combat Units 98,000 86,000 184,000

Support Units 100,000 40,000 141,000

Overheada 119,000 48,000 167,000 ________ ________ ________

Total 317,000 174,000 491,000

Reserve

Component Total

Active

Component
84 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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States has engaged in over the past few decades, opponents have chosen to safeguard their air forces by keeping 

them grounded for the duration of the conflict. In addition, few nations currently have ground-based air 

defenses capable of seriously hindering U.S. air operations. The United States has faced only limited competition from hostile fighter aircraft since 1950 (when China 

intervened in the Korean War), and it has been able to 

overcome every opposing country’s air-defense systems. 

In the majority of U.S. conflicts since World War II, U.S. 

air forces have been able to operate essentially at will, 

either from the beginning of the conflict or a short time 

thereafter, once the opponent’s air defenses had been 

destroyed.6 (For a discussion of those and other past 

military operations, see Appendix C.)

The United States has historically had a lower threshold 

for using air and naval forces in combat than for using 

ground forces. And although flexibility and response time 

have made aircraft carriers a commonly used option for 

conducting aerial attacks in small interventions, Air Force 

aircraft have played a role in almost every U.S. conflict 

since the service was created. Through international 

agreements, the United States has access to an extensive 

network of air bases around the world. In addition, the 

Air Force’s tanker fleet is capable of extending the range 

of Air Force aircraft to allow attacks on almost any possible hostile country. Air Force squadrons can also be 

deployed more quickly than ground forces, and their ability to fly at high speeds to distant locations allows them 

to put virtually any location at risk of attack (provided 

that its air defenses have been sufficiently degraded or can 

be avoided).

Views on the use of air power have long fallen into two 

major camps, one focused on strategic airpower (generally associated with the Air Force) and the other focused 

on tactical airpower (generally associated with the other 

military services). Both schools of thought agree that the 

first priority in any air campaign is to destroy enemy 

fighter aircraft and air-defense systems to ensure that U.S. 

air forces can operate freely in enemy airspace. Beyond 

achieving air superiority, however, the two schools have 

very different views on the form that airpower should 

take and the way it should be used in a conflict; they also 

have very different historical records. (The terms “strategic airpower” and “tactical airpower” originated from a 

time when the former was largely synonymous with longrange bombers and the latter with fighters. Modern aircraft have blurred that distinction, so those terms might 

be more accurately called “strategic use of airpower” and 

“tactical use of airpower.” However, CBO uses the more 

common terms here for simplicity.)

Strategic Airpower. Strategic airpower is a catchphrase 

for attempts to use air power to win a conflict directly—

independent of naval and ground forces—either by 

severely limiting an opponent’s ability to conduct effective military operations or by coercing the opponent’s 

leaders into acceding to U.S. demands. In that school of 

thought, the main way to achieve those ends is generally 

through bombardment of “strategic” targets, such as 

command-and-control assets, infrastructure, or key 

components of an adversary’s economy. Consequently, 

proponents of strategic airpower have historically favored 

long-range bombers (although it is possible to employ 

tactical aircraft to attack strategic targets) and have 

regarded attempts to use airpower to influence ground 

battles as a diversion from the primary air campaign of a 

conflict.

The effectiveness of strategic airpower has been hotly 

debated for decades. Proponents cite a number of theories and point to various examples—such as the ending of 

World War II after U.S. nuclear attacks on Japan and the 

1999 air campaign intended to force Serbia to withdraw 

from Kosovo—as evidence that air forces can win wars 

largely independent of naval or ground campaigns. Proponents generally also assert that having the ability to win 

wars through the use of strategic airpower is a highly 

appealing strategy given U.S. preeminence in the air and 

the tendency of airpower to result in fewer U.S. casualties 

than traditional ground campaigns. (Some advocates of 

strategic airpower also contend that, in an era of precision 

munitions, an air campaign can result in fewer enemy 

civilian casualties as well, making it a more humanitarian 

option than a ground campaign. That position is 

controversial, however.)

The use of air forces alone to conduct strikes on opposing 

states, without the commitment of U.S. or allied ground 

forces, has had mixed results in achieving the United 

States’ strategic goals. Although air strikes or cruise missile strikes by themselves have sometimes been able to 

achieve more limited U.S. goals, opponents of strategic 

6. A notable exception was the Vietnam War, in which the U.S. military did not maintain a vigorous effort to neutralize North Vietnam’s air defenses. Despite those defenses, the United States was 

able to conduct substantial air operations.
CHAPTER 4: DEPARTMENT OF THE AIR FORCE THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 85

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airpower point to numerous operations without ground 

forces in which the United States failed to achieve its 

aims. Examples include U.S. bombing of North Vietnam 

between 1969 and 1973 and cruise missile attacks in 

Afghanistan and Sudan in 1998 (Operation Infinite 

Reach). Some theorists have argued that the credible 

threat of attack by ground forces is a necessary component of a strategy focused on strategic air attacks. In 

recent years, the United States has often sought out local 

ground forces to assist in operations that do not involve 

U.S. ground forces, as it did in Afghanistan in 2002 and 

Libya in 2011 and as it has recently tried to do in Syria.

Tactical Airpower. Tactical airpower is a catchphrase for 

attempts to use air power in support of naval and ground 

forces, to assist in winning a conflict by amplifying the 

power of those forces (generally through attacks on an 

opponent’s ground forces or naval vessels). Proponents 

of tactical airpower have historically favored short-range 

fighter aircraft (although bombers can be used in this role 

as well) and have regarded attempts to use air power to 

prosecute a separate air campaign as a diversion from the 

primary naval or ground campaign in a conflict.

Tactical airpower is often described as having a powerful 

synergy with ground forces. The reason is that methods 

for defending against ground forces make an opponent 

more vulnerable to attacks from the air, and methods for 

defending against attacks from the air make an opponent 

more vulnerable to ground forces. During the combat 

phase of Operation Iraqi Freedom, for example, DoD 

sources frequently illustrated that synergy when describing how U.S. ground forces could pressure Iraqi units to 

respond to their assaults. Hostile ground forces are more 

vulnerable to airpower when they are moving (because 

soldiers are not protected by field fortifications, vehicles 

travel in clusters on roads, and so forth), whereas they can 

sometimes resist aerial attack very effectively when they 

are stationary. But if they are trying to defend against 

mobile U.S. ground forces, hostile ground forces may 

need to move to protect key locations or to keep from 

being surrounded. In a similar vein, hostile ground forces 

can resist aerial attack much more easily if they are widely 

dispersed, but such dispersion makes it much harder for 

them to resist attack from other ground forces. Those 

synergies mean that combining tactical airpower with 

ground forces makes the application of tactical airpower 

much more effective than it would be otherwise. Tactical 

airpower has also long been thought to be decisive in naval 

combat. Examples include the United States’ experience in 

such World War II battles as Pearl Harbor and Midway 

and Britain’s experience during the Falklands War.7

Although strategic and tactical airpower can be seen as 

competing approaches, U.S. air forces have used a hybrid 

approach during recent conflicts, attacking the sorts of 

targets favored by both groups of airpower proponents. 

Part of the reason is that modern U.S. air operations have 

generally been limited not by the number of air assets 

available (which would force the military to make choices 

between competing sets of targets) but instead by the 

amount and quality of information that can be gathered 

about prospective targets.

What This Chapter Covers

The rest of this chapter presents CBO’s analysis of the 

following major elements of the Air Force’s force structure (listed here with the percentage of the Department 

of the Air Force’s O&S costs that they account for):

B Tactical aviation squadrons (33 percent); see page 86.

B Bomber squadrons (10 percent); see page 89.

B Airlift squadrons (15 percent); see page 92.

B Air refueling squadrons (14 percent); see page 96.

B Unmanned air systems (6 percent); see page 100.

B Other units and activities of the Department of the 

Air Force, such as intercontinental ballistic missiles and 

special-operations forces (21 percent); see page 103.

This chapter also examines one topic of special concern 

to the Air Force: the modern U.S. military’s strike capability, which allows many different types of aircraft to 

attack and destroy a wide range of ground targets; see 

page 105.

7. The Navy and Air Force have had few opportunities to cooperate 

in large-scale naval battles since World War II, partly because of 

the absence of significant naval opponents since then and partly 

because of the capability and large quantity of U.S. naval aircraft. 

However, in recent years, the two services have developed an 

“Air-Sea Battle” concept to develop ways to integrate their forces 

in future conflicts.
86 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Air Force Tactical Aviation Squadrons

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size). 

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. Because F-35s are not yet in full operational service, their actual costs may differ from the planned costs included in the Department of Defense’s 

budget documents, on which these estimates are based.

Tactical aircraft, which make up the majority of the Air 

Force’s combat fleet, consist of relatively small aircraft 

designed to engage in air-to-air combat (fighters), to 

strike targets on the ground (attack aircraft), or both 

(multirole aircraft, which the Air Force designates as 

fighters). 

Current and Planned Structure. Between its active and 

reserve components, the Air Force plans to field the 

equivalent of about 101 notional 12-aircraft squadrons of 

tactical aviation in 2017, consisting of 185 attack aircraft 

(A-10s) and 1,019 fighter aircraft (294 F-15s, 537 F-16s, 

157 F-22s, and 31 F-35s). The number of notional 

squadrons is expected to decline slightly in the next few 

years, mostly because of the planned retirement of the 

A-10 fleet, and then rise back to 100 squadrons by 2021 

as production of F-35s increases. (For an example of the 

structure of a tactical aviation squadron, see Figure 4-1.) 

Tactical aviation accounts for about 33 percent of the Air 

Force’s total operation and support funding.

Purpose and Limitations. In the past, most types of tactical aircraft were highly specialized for either air-to-air or 

air-to-ground combat. Today, those two forms of combat

Military Personnel per Unit 1,190 350 440 400

Annual Cost per Unit 230 80 60 90

(Millions of 2017 dollars)

Military Personnel per Unit 1,540 430 590 520

Annual Cost per Unit 300 100 80 120

(Millions of 2017 dollars)

Military Personnel per Unit 1,250 450 370 420

Annual Cost per Unit 220 70 50 100

(Millions of 2017 dollars)

Military Personnel per Unit 2,390 430 1,150 810

Annual Cost per Unit 470 120 160 190

(Millions of 2017 dollars)

Military Personnel per Unit 2,940 430 1,510 1,000

Annual Cost per Unit 570 130 210 230

(Millions of 2017 dollars)

Total Direct Overhead Indirect

A-10 Attack Aircraft Squadron

F-15 Fighter Aircraft Squadron

F-16 Fighter Aircraft Squadron

F-22 Fighter Aircraft Squadron

F-35 Fighter Aircraft Squadrona
CHAPTER 4: DEPARTMENT OF THE AIR FORCE THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 87

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Figure 4-1.

Aircraft and Personnel in Notional Air Force Tactical Aviation Squadrons 

Source: Congressional Budget Office, using data from the Department of Defense.

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size).

are still the main roles for the Air Force’s tactical aviation 

fleet, but the most numerous type of aircraft in the fleet is 

a multirole aircraft (the F-16). Only a small portion of 

the tactical aviation fleet consists of purely attack aircraft 

(A-10s). Moreover, the Air Force’s newest air-to-air 

fighter (the F-22) was designed with some ground-attack 

capability. The emphasis on multirole aircraft is likely to 

continue in the future with the introduction of the F-35, 

which was designed primarily to attack ground targets 

but has air-to-air capability as well. (The ground-attack 

mission is discussed in detail in the special-topic entry 

about strike capability on page 105.) 

Despite their versatility, multirole fighters are most likely 

to be used for specific missions according to their individual strengths. For example, F-22 fighters are considered 

best suited to perform the most difficult air-to-air combat 

missions, and F-16s and F-35s are best suited to carry out 

ground-attack missions.

A-10 attack aircraft have almost no air-to-air combat ability; they were designed mainly to provide air support for 

friendly ground forces (by attacking hostile ground forces 

engaged in combat). The A-10 is noteworthy for its large 

cannon, a 30-millimeter (mm) Gatling gun designed for 

A-10 Attack Aircraft

F-15 Fighter Aircraft

F-16 Fighter Aircraft

F-22 Fighter Aircraft

F-35 Fighter Aircraft

= 100 Personnel

0 100 300 400 500 feet 200
88 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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attacking armored combat vehicles. (By comparison, 

other types of Air Force tactical aircraft have a 20 mm 

Gatling gun.) A-10s have good visibility from the cockpit 

and can fly relatively slowly, factors that give pilots an 

excellent view of the battlefield they are supporting. 

However, in recent years, the Department of Defense 

proposed retiring the A-10 fleet, arguing that those aircraft cannot withstand modern air defenses and are too 

expensive to maintain in the force.8

F-15 fighter aircraft come in several versions, including 

the C model (“Eagle”), intended mainly for air-to-air 

combat, and the E model (“Strike Eagle”), intended 

mainly for ground-attack missions. Until the introduction of the F-22, the F-15C was the Air Force’s primary 

vehicle for achieving air superiority in a theater of operations; it is still considered a highly capable fighter plane. 

The F-15E model is a relatively large strike aircraft—by 

the standards of tactical aviation—with a fairly long 

range and large capacity for carrying bombs and extra 

fuel.

F-16 fighters are the most numerous aircraft in the Air 

Force’s tactical aviation fleet. Originally designed as a 

low-cost air-to-air fighter that could operate only during 

daylight hours, the F-16 has evolved into a very effective 

multirole fighter that can operate at any time of the day. 

F-16s are relatively small and lightweight, with a correspondingly limited range and payload capacity. Part of 

the F-16 fleet has been upgraded with specialized equipment for attacking and suppressing enemy air-defense 

systems.

F-22 fighters are the Air Force’s newest aircraft designed 

specifically for air-to-air combat. They incorporate 

“stealth” design characteristics that make them difficult to 

observe with radar, and they are generally considered the 

most capable air-to-air combat aircraft being fielded by 

any nation. The F-22 was initially designed with limited 

ground-attack capability, but the Air Force has been 

modifying the aircraft to improve that capability.9

The F-35A, the Air Force’s variant of the Joint Strike 

Fighter, is currently in production but is not slated to 

enter service until 2017 (the first few aircraft are now 

being used for testing and training). The F-35 is intended 

to replace the A-10 and F-16 as the Air Force’s main tactical strike platform. The largest improvement it provides 

is stealth; once fielded, it will give the Air Force a large 

fleet of hard-to-observe strike aircraft. The F-35A will 

also be capable of air-to-air combat, although not to the 

same degree as the F-22. Capabilities that the F-35A will 

not offer are a cannon comparable to that of the A-10 

and the slow flying speed useful for finding and attacking 

ground targets.10

Past and Planned Use. The Air Force’s tactical aircraft 

have been used extensively in almost every conflict in 

which the United States has taken part since the 1940s. 

Likewise, most potential scenarios for future conflicts 

are likely to include the heavy use of tactical aviation. In 

general, tactical aircraft are responsible for securing U.S. 

control of the air (by destroying an opponent’s air forces 

and air defenses) and for supporting U.S. war efforts 

by attacking ground targets. In a few cases, such as the 

enforcement of “no-fly zones,” securing U.S. control of 

the air is the sole mission. That mission is overwhelmingly the responsibility of Air Force tactical aviation. 

8. Through prohibitions in national defense authorization acts, the 

Congress has so far not allowed the Air Force to carry out plans to 

retire the A-10 fleet. In its 2017 budget request, the Air Force did 

not propose to retire the A-10 fleet as rapidly.

9. Generally speaking, for a combat aircraft to be stealthy, the 

bombs, missiles, and other ordnance it carries must fit inside 

an internal bay rather than being carried externally. The F-22’s 

internal bays are small relative to the size of many air-to-ground 

weapons (and the aircraft has no external mounting points for 

such ordnance). Thus, even after it has been upgraded for strike 

missions, the F-22 will carry smaller amounts of air-to-ground 

ordnance than other tactical fighters can. 

10. Like the F-22, the F-35A will have to carry ordnance in a relatively small internal bay to retain its stealth characteristics, 

although the aircraft’s bay has been sized to accommodate most 

types of air-to-ground weapons. Unlike the F-22, the F-35 has 

external mounting points available, so if stealth is not necessary (as 

may be the case after hostile air defenses have been suppressed), 

the F-35 can carry an ordnance load comparable to that of other 

tactical aircraft.
CHAPTER 4: DEPARTMENT OF THE AIR FORCE THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 89

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Major Element of the Force Structure

Air Force Bomber Squadrons

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size). 

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

The Air Force’s bomber fleet has two main roles: delivering nuclear weapons and performing strikes with conventional weapons. (Those strike missions are discussed in 

more detail at the end of this chapter, and the nuclear 

weapons capability of the U.S. military is discussed in the 

next chapter.) Historically, the Air Force viewed the delivery of nuclear weapons as the primary purpose of longrange bombers, with conventional strikes as a secondary 

role. However, events since the collapse of the Soviet 

Union have generally increased the emphasis on conventional strike missions for the bomber fleet. One of the Air 

Force’s three types of long-range bombers, the B-1B, is no 

longer capable of delivering nuclear weapons and is now 

devoted entirely to conventional strike missions. In addition, many of the Air Force’s B-52s are slated for conversion to a conventional-only configuration to comply with 

the New START arms control treaty.

Current and Planned Structure. Between its active 

and reserve components, the Air Force plans to field the 

equivalent of about 9 notional 12-aircraft squadrons of 

long-range bombers in 2017, consisting of 45 B-52s, 

51 B-1Bs, and 16 B-2s. It has no plans to change the 

number of notional squadrons through 2021. (For an 

example of the structure of a bomber squadron, see 

Figure 4-2.) Bombers account for about 10 percent of the 

Air Force’s total operation and support funding. 

Purpose and Limitations. Unlike tactical aviation, 

bombers are large aircraft that can travel long distances 

and loiter above an area for an extended period without 

refueling (characteristics referred to as endurance) and 

can deliver a large payload of munitions. Those capabilities make bombers especially well-suited to performing 

strike missions—their long range allows them to be based 

relatively far from the theater of operations (freeing up 

space in closer air bases for shorter-range aircraft); their 

loitering time lets them remain in an area longer, allowing 

them to respond more rapidly to requests from ground 

forces for air support; and their large load of munitions 

enables them to provide substantial air support before 

needing to return to bases to rearm.

The enormous weapons payload of the bomber fleet 

allows it to contribute a very substantial share of the 

U.S. military’s capability to strike targets, despite its relatively small numbers. For example, a B-1B can carry 

84 500-pound bombs in a single sortie, whereas an F-16

Military Personnel per Unit 3,830 1,310 1,220 1,300

Annual Cost per Unit 740 270 170 300

(Millions of 2017 dollars)

Military Personnel per Unit 3,980 940 1,680 1,350

Annual Cost per Unit 810 270 230 310

(Millions of 2017 dollars)

Military Personnel per Unit 8,660 2,120 3,600 2,940

Annual Cost per Unit 1,840 670 490 680

(Millions of 2017 dollars)

Total Direct Overhead Indirect

B-52 Bomber Aircraft Squadron

B-1B Bomber Aircraft Squadron

B-2 Bomber Aircraft Squadron
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Figure 4-2.

Aircraft and Personnel in Notional Air Force Bomber Squadrons

Source: Congressional Budget Office, using data from the Department of Defense.

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size).

B-1B Bombers

B-52 Bombers

= 100 Personnel

0 100 300 400 500 feet 200

B-2 Bombers
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could carry 12, although an F-16 typically flies more 

sorties per day and thus could deliver those 12 bombs 

more often. However, the Air Force can capitalize on 

bombers’ large payloads only on missions in which 

enough targets can be identified to use the number of 

weapons carried.

B-52s are the oldest of the Air Force’s bombers, dating to 

the 1960s.11 The Air Force plans to keep them in service 

at least through 2040. B-52s have the ability to carry a 

great variety of weapons and have the longest unrefueled 

endurance of the Air Force’s bomber fleet. Because of 

their age, however, B-52s would probably have trouble 

penetrating modern air-defense systems and thus are best 

suited to operating in undefended airspace or to delivering cruise missiles from outside defended airspace.12

The B-1B fleet is younger than the B-52 fleet, having 

been built in the 1980s. Although B-1Bs were designed 

to deliver nuclear weapons, the United States modified 

them to remove that capability in order to comply with 

arms control treaties. Today, B-1Bs are intended only to 

perform conventional strikes. Although they incorporate 

some features that make them harder to observe than 

B-52s, they are not considered as capable of surviving in 

hostile airspace as the more recent B-2s. Nevertheless, the 

Air Force has used B-1Bs to conduct air strikes in hostile 

airspace in recent operations—the B-1B fleet delivered 

more bombs in Operation Iraqi Freedom than any other 

type of aircraft—albeit often with support from other 

aircraft.

B-2s are the newest and most modern U.S. bombers. 

Built in the late 1980s and the 1990s, they are notable 

for the extensive stealth design features that help them 

penetrate hostile airspace undetected, and they are considered more difficult to target and attack than other U.S. 

bombers. However, unlike with other bombers, the Air 

Force is reluctant to deploy B-2 squadrons to bases overseas, preferring to have them conduct strikes directly 

from their base in Missouri. Two reasons, according to 

the Air Force, are the planes’ demanding maintenance 

requirements (associated with the special radar-absorbing 

coating on the outside of the aircraft) and the need for 

atmospherically controlled hangars. Nevertheless, the B-2 

can be deployed overseas, if necessary, and has been on 

occasion. In practice, flying most missions from U.S. 

bases means that B-2 sorties are extremely long and 

demanding, which limits the number of sorties that the 

small B-2 fleet (16 aircraft) can conduct to those in which 

stealth is most essential.

Past and Planned Use. Air Force bombers have been 

employed with increasing frequency in modern U.S. 

conflicts. Their use was relatively limited in Operation 

Desert Storm—B-52s delivered cruise missiles during the 

initial wave of strikes and conducted some bombing missions afterward—but at the time, the Air Force still saw 

bombers as primarily dedicated to nuclear missions. Since 

then, with the collapse of the Soviet Union, bombers 

have been used in larger roles in more conflicts. For 

example, the B-1B fleet was first employed for conventional air strikes during the 1990s enforcement of no-fly 

zones over Iraq; later it was used during operations in 

Kosovo, in Operations Enduring Freedom and Iraqi 

Freedom, and in the subsequent occupations of 

Afghanistan and Iraq. The B-2 fleet was first employed 

for conventional strikes in Kosovo and was also used during Operations Enduring Freedom and Iraqi Freedom. 

(It is not clear whether B-2s played a role in the subsequent occupations of Afghanistan and Iraq.) B-52s have 

often been mentioned as being particularly useful during 

the occupations of Afghanistan and Iraq because their 

large fuel load allows them to remain on station, waiting 

for requests for fire support, for long periods.

11. The earliest models of the B-52 were introduced in the 1950s, but 

those models have since been retired.

12. Although B-52s have sometimes been used to launch cruise missiles from outside heavily defended airspace, that role is generally 

performed by the Navy, which has extensive capability to fire 

Tomahawk cruise missiles from long range.
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Major Element of the Force Structure

Air Force Airlift Squadrons

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size). 

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

The Air Force’s fleet of cargo aircraft exists to “airlift” 

(transport by air) personnel and equipment between or 

within theaters of operations. Intertheater transport is 

generally conducted by the larger, longer-range, and more 

expensive C-5 and C-17 aircraft. Intratheater transport is 

usually performed by the smaller, shorter-range, and 

less expensive C-130 aircraft, although the C-17 was 

designed to operate from shorter runways, making it an 

option for transport missions between theaters as well. 

Current and Planned Structure. Between its active 

and reserve components, the Air Force plans to field the 

equivalent of about 42 notional 12-aircraft squadrons 

of cargo aircraft in 2017, consisting of 292 C-130s, 

39 C-5s, and 172 C-17s. That total number is planned 

to increase slightly, to 43 squadrons, by 2021. (For an 

example of the structure of such a squadron, see 

Figure 4-3 on page 94.) Cargo aircraft account for about 

16 percent of the Air Force’s total operation and support 

funding.

To supplement its airlift capabilities, the Air Force runs 

a program called the Civil Reserve Air Fleet (CRAF). 

Under that program, U.S. civilian air carriers that operate 

certain models of aircraft receive preferential access to air 

transport contracts with the Department of Defense; in 

return, those carriers allow the Air Force to use their aircraft for military transport missions in times of conflict. 

The CRAF program ensures that the Air Force has a large 

reserve of transport aircraft available in situations in 

which it may need more airlift capability than its own 

fleet can provide. Most eligible U.S. civilian airlines participate in the CRAF program, which generally gives the 

Air Force access to an additional 400 intertheater transport aircraft and 100 intratheater transport aircraft 

(although the numbers vary over time). 

Because CRAF aircraft are designed for civilian use, they 

are not suitable for certain military missions, such as 

transporting the largest armored vehicles. But for some 

purposes, such as carrying passengers, CRAF aircraft are 

frequently a better alternative in times of conflict than the 

Air Force’s transport aircraft.

Purpose and Limitations. The primary advantage of 

moving cargo and passengers by air is that it is much 

faster than transport by sea. In many scenarios for possible conflicts, the use of air transport would let U.S. forces 

reach a theater of operations within a day, rather than the 

weeks that sea transport might require. In addition, 

Military Personnel per Unit 2,120 800 590 720

Annual Cost per Unit 360 110 80 170

(Millions of 2017 dollars)

Military Personnel per Unit 2,430 780 820 830

Annual Cost per Unit 430 130 110 190

(Millions of 2017 dollars)

Military Personnel per Unit 1,390 450 460 470

Annual Cost per Unit 270 90 60 110

(Millions of 2017 dollars)

Total Direct Overhead Indirect

C-130 Cargo Aircraft Squadron

C-5 Cargo Aircraft Squadron

C-17 Cargo Aircraft Squadron
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aircraft can move supplies to almost any portion of the 

globe, whereas many theaters of operations (such as 

Afghanistan) are far from the sea and would require additional land transportation to move personnel and cargo 

from ports to the theater. Even in an ongoing operation, 

the speed and responsiveness of air transport can be 

extremely valuable in providing logistics support—for 

example, being able to bring in crucial supplies on a day’s 

notice is preferable to needing a month’s notice. 

To minimize deployment times, virtually all U.S. military 

personnel are deployed to and from theaters of operations 

by air. Moving cargo, however, by air has two major disadvantages. First, cargo aircraft are much more expensive 

to purchase and operate than the equivalent amount of 

sea transport capacity. Second, although air transport is 

less subject to geographical constraints than sea transport, 

it can be subject to infrastructure constraints, such as limited numbers or quality of airfields. Because the United 

States has a large fleet of cargo aircraft (and has access to 

an even larger fleet through the CRAF program) but 

often operates in regions with poor infrastructure, the 

Air Force’s ability to airlift equipment is frequently limited not by how many cargo aircraft it has but by the 

quality and quantity of airports available in the theater of 

operations. Many countries and regions do not have 

enough airports with the capacity to accommodate the 

flow of large cargo aircraft the military might need. 

Often, there are few airports, with small numbers of airstrips of insufficient size or strength and limited facilities 

for cargo operations. The Air Force has engineering units 

that can improve the capacity of those airports over time. 

Nevertheless, in most potential conflicts outside highly 

developed areas (such as Western Europe, Japan, or 

South Korea), the capacity of local airports tends to be 

the factor that limits cargo volume.13

Past and Planned Use. The Air Force’s cargo aircraft 

have been employed extensively in every U.S. conflict 

in the modern era. Notable examples include the use of 

those aircraft to rapidly deploy elements of the 82nd 

Airborne Division to Saudi Arabia in 1990 after the Iraqi 

invasion of Kuwait and the parachuting of special-forces 

personnel into Afghanistan in 2001 during the early 

phases of U.S. operations there. The U.S. military has 

relied especially heavily on air transport throughout 

its operations in Afghanistan because that country is 

landlocked, with the closest access to seaports being in 

neighboring Pakistan.

Most of DoD’s potential scenarios for future conflicts 

envision heavy reliance on air transport. DoD has set several goals over the years for the amount of air transport 

capability it needs. The analytic measure generally used 

to assess the capacity of the airlift fleet is ton-miles per 

day (the ability to transport 1 ton of cargo 1 mile every 

day). That measure can be difficult to translate into numbers of aircraft because it depends greatly on the characteristics of a given scenario.14 In general, however, because 

the U.S. military’s ability to transport cargo to a theater 

of operations is more likely to be limited by the infrastructure in that theater than by the number of aircraft in 

the Air Force’s inventory, a larger inventory of cargo aircraft would allow the United States to support more 

operations simultaneously or to reduce reliance on CRAF 

aircraft. Conversely, a smaller inventory of cargo aircraft 

would either lessen the Air Force’s ability to support large 

operations in multiple theaters simultaneously or require 

greater reliance on CRAF aircraft.

13. In cases in which a friendly government seeks U.S. protection 

from hostile neighbors, it is possible to improve infrastructure 

during peacetime in anticipation of a possible conflict. For 

example, Saudi Arabia cooperated with the United States to 

improve its infrastructure for sea and air transport in the 1980s 

and 1990s so U.S. forces could respond more effectively if the 

country was threatened. 

14. Broadly speaking, scenarios involving more distant locations 

require more transport aircraft to move a force of a given size in a 

given amount of time. Thus, the number of transport aircraft 

needed to respond to a crisis in, say, Southeast Asia would be 

larger than the number needed to respond to a crisis in Latin 

America. As a result, the number of transport aircraft that the 

U.S. military needs depends critically on where DoD foresees 

crises emerging.
94 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Figure 4-3.

Aircraft and Personnel in Notional Air Force Airlift Squadrons

Continued

C-5 Cargo Aircraft

C-130 Cargo Aircraft
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Figure 4-3. Continued

Aircraft and Personnel in Notional Air Force Airlift Squadrons

Source: Congressional Budget Office based on data from the Department of Defense.

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size).

= 100 Personnel

0 100 300 400 500 feet 200

C-17 Cargo Aircraft 
96 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Air Force Air Refueling Squadrons

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size). 

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. Because KC-46s are not yet in full operational service, their actual costs may differ from the planned costs included in the Department of Defense’s 

budget documents, on which these estimates are based.

The tanker fleet exists primarily to refuel the Air Force’s 

other aircraft while they are in flight. Although the fleet 

was originally established to refuel strategic bombers on 

long-range nuclear strike missions into the Soviet Union, 

tankers have proved valuable for refueling tactical aircraft 

in almost every U.S. operation of the post–Cold War era. 

In addition, all of the Air Force’s tankers are capable of 

transporting cargo as a secondary mission.

Current and Planned Structure. Between its active and 

reserve components, the Air Force plans to field the 

equivalent of about 36 notional 12-aircraft squadrons of 

tanker aircraft in 2017, consisting of 357 KC-135s, 

54 KC-10s, and 16 KC-46s. The number of notional 

squadrons is set to remain roughly steady through 2021 

as KC-46 tankers are introduced and some KC-10s are 

retired. (For an example of the structure of a tanker 

squadron, see Figure 4-4 on page 98.) Tanker aircraft 

account for about 14 percent of the Air Force’s total 

operation and support funding.

Purpose and Limitations. Without aerial refueling, 

tactical aircraft would typically have ranges of only a few 

hundred miles, so they would have to be based close to 

their areas of operations, would have less ability to loiter 

in a location for very long during a mission, and in some 

cases would have to reduce the weight of the weapons 

they carried. With aerial refueling, by contrast, the 

endurance (range and loitering time) of tactical aviation 

is limited largely by pilots’ endurance, and aircraft can be 

fully loaded with weapons. Those differences increase the 

utility of tactical aircraft during a conflict in various ways:

B In many theaters, infrastructure constraints limit how 

many tactical aircraft the United States can deploy 

near an area of operations. Aerial refueling expands the 

number of bases from which tactical aircraft can reach 

a given area, allowing the United States to use more 

tactical aircraft in a conflict than it could otherwise.15

Military Personnel per Unit 1,930 610 660 650

Annual Cost per Unit 360 110 90 150

(Millions of 2017 dollars)

Military Personnel per Unit 3,140 900 1,170 1,060

Annual Cost per Unit 580 180 160 250

(Millions of 2017 dollars)

Military Personnel per Unit 1,070 640 70 360

Annual Cost per Unit 180 80 10 80

(Millions of 2017 dollars)

KC-135 Tanker Aircraft Squadron

KC-10 Tanker Aircraft Squadron

KC-46 Tanker Aircraft Squadrona

Total Direct Overhead Indirect

15. Similarly, naval aircraft operating from carriers would be unable to 

reach areas of operations far inland, such as Afghanistan, without 

aerial refueling by Air Force tankers. The Navy currently relies on 

a system known as “buddy tanking” that uses some of the fighter 

aircraft in a carrier air wing to refuel other fighter aircraft. However, using tactical aircraft in that way offers a much more limited 

ability to expand the range of tactical aircraft.
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B An aircraft’s fuel consumption increases when it carries 

a heavy load of weapons; aerial refueling can reduce 

the need to make trade-offs between the number of 

weapons an aircraft can carry and the distance it can 

carry them.16

B In many types of missions, it is beneficial for tactical 

aircraft to be able to loiter, on call, until needed so 

they can respond more rapidly to requests from 

ground forces for air support. Aerial refueling can 

enhance the U.S. military’s effectiveness in those types 

of missions by allowing tactical aircraft to loiter for 

longer periods.

B In some large theaters, tactical aircraft would be 

unable to reach distant targets at all without aerial 

refueling.

Bombers are larger than tactical aircraft and have longer 

ranges, but aerial refueling offers some of the same 

benefits to bomber missions. For example, B-2 bombers 

require specialized basing infrastructure that makes them 

difficult to deploy overseas. But with aerial refueling, B-2 

bombers can strike targets anywhere in the world from 

their base in Missouri.

The Air Force’s transport aircraft generally do not require 

aerial refueling, although it is possible and might improve 

the efficiency of airlift operations in some situations. Aerial refueling also helps U.S. deployments to overseas theaters indirectly by allowing some shorter-range aircraft to 

“self-deploy” (be flown themselves to the theater) rather 

than needing to be carried there on a cargo plane or ship.

One limitation of the current aerial refueling fleet is that 

its tankers are large and slow with few defenses. During a 

conflict in which the United States had not yet neutralized an opponent’s fighter aircraft, tankers would be vulnerable to attack. In practice, however, the United States 

has not faced any major aerial threats since the end of the 

Cold War, so that limitation has not been significant.

Another drawback of the U.S. tanker fleet results from 

the use of two different, and incompatible, methods of 

aerial refueling. The Navy and Marine Corps employ 

“probe and drogue” refueling systems on their tankers, 

fixed-wing aircraft, and rotary-wing aircraft, whereas 

the Air Force employs a “boom” refueling system on its 

tankers, tactical aircraft, and bombers.17 Many Air Force 

tankers are also equipped to allow for probe-and-drogue 

refueling, so they can refuel tactical aircraft from the 

Navy and Marine Corps during operations. However, 

the need to accommodate both systems in joint operations requires the Air Force to equip some tankers to 

make them capable of both methods—at a higher cost 

than would be necessary otherwise—and to coordinate 

to ensure that the correct types of tankers are assigned to 

support the correct types of aircraft.

Past and Planned Use. The Air Force’s tanker aircraft 

have been used extensively in every major U.S. conflict 

since the 1960s. Tankers were especially important in 

operations such as the invasion of Afghanistan, in which 

the United States had very limited access to air bases near 

the area of operations, so aerial refueling was vital to 

enable the Air Force’s tactical aircraft and the Navy’s carrier aircraft to attack targets in the theater. Many of the 

Department of Defense’s potential scenarios for future 

conflicts also envision heavy reliance on aerial refueling.

Although the Air Force’s tanker fleet is large, it tends to 

be quite old. The bulk of the fleet consists of KC-135s 

built in the 1950s and 1960s. (Until the end of the Cold 

War and Operation Desert Storm in 1991, the Air Force 

mainly saw tankers as useful for supporting a nuclear 

attack on the Soviet Union rather than for supporting 

tactical aviation in ongoing conflicts.) Leaders of the Air 

Force have often stated that KC-135s are too old and 

need to be replaced immediately, but many analysts have 

suggested that those tankers are in good enough shape to 

continue serving for many years. Consequently, the major 

issue relating to the future of the tanker fleet is not its size 

but the speed with which the Air Force should replace the 

KC-135 with the new KC-46, which is in development.

16. For example, one specific trade-off is that most tactical aircraft can 

carry external fuel tanks to extend their range, but those tanks add 

weight to the aircraft, reduce the number of weapons it can carry, 

and decrease its in-flight performance. It is generally considered 

preferable to minimize the number and size of external fuel tanks, 

and aerial refueling often allows that.

17. In probe-and-drogue systems, the tanker tows a hose with a receptacle at the end, and the receiving aircraft has a probe that fits into 

the receptacle. Such systems are relatively lightweight, can be fitted on smaller aircraft, and can refuel more than one small plane 

at a time. They are also the only option for refueling rotary-wing 

aircraft. In boom systems, by contrast, the tanker has a boom that 

fits into a receptacle on the receiving aircraft. Those systems are 

relatively heavy, are only fitted on larger tankers, and can refuel 

just one aircraft at a time. However, they also transfer fuel more 

quickly and are the preferred method for refueling large planes, 

such as bombers or cargo aircraft.
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Figure 4-4.

Aircraft and Personnel in Notional Air Force Air Refueling Squadrons

Continued

KC-10 Tankers

KC-135 Tankers
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Figure 4-4. Continued

Aircraft and Personnel in Notional Air Force Air Refueling Squadrons

Source: Congressional Budget Office, using data from the Department of Defense.

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size).

KC-46 Tankers

= 100 Personnel

0 100 300 400 500 feet 200
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Major Element of the Force Structure

Air Force Unmanned Air System Squadrons

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size). 

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

The Department of Defense uses unmanned air systems 

(UASs)—also known as unmanned aerial vehicles or 

drones—mainly for surveillance and intelligence gathering. Each of the military departments operates a variety 

of unmanned aircraft, but the Air Force’s models tend to 

be larger and to possess greater endurance and payload 

capacity. 

Current and Planned Structure. Between its active and 

reserve components, the Air Force plans to field about 

75 notional 12-aircraft UAS squadrons in 2017. Those 

aircraft consist of 110 MQ-1s, 36 RQ-4s, and 279 MQ-9s. 

The number of notional squadrons is expected to decline 

to 30 by 2021 as the Air Force retires its MQ-1s. (For 

an example of the structure of a UAS squadron, see 

Figure 4-5.) Unmanned air systems account for about 

6 percent of the Air Force’s total operation and support 

funding.18

In addition to those aircraft, the Air Force has acknowledged that it operates at least one other type of UAS, a 

stealthy aircraft called the RQ-170. The quantities and 

characteristics of that system remain classified.

Purpose and Limitations. The Air Force’s unmanned 

aircraft are used primarily for surveillance. In addition, 

MQ-1s and MQ-9s can be armed with a few missiles or 

small bombs to conduct limited strike operations. An 

example of that capability is the United States’ wellpublicized use of unmanned aircraft to kill suspected terrorists in Pakistan, Yemen, Somalia, and other countries. 

(Little information about such attacks has been released 

publicly, but it appears that many of those attacks have 

been conducted by the Central Intelligence Agency rather 

than by DoD. Those drones form a separate UAS fleet 

from the Air Force’s and are not covered in this report.)

Today’s drones have several advantages: They are generally less expensive to buy than manned aircraft, they 

can fly very long missions without being limited by the 

endurance of human aircrews, and they can operate without putting a pilot at risk of injury, capture, or death. 

Disadvantages of drones include their vulnerability to air 

defenses and the lack of a human onboard to address 

split-second issues in ways that might not be possible by a

Military Personnel per Unit 260 90 80 90

Annual Cost per Unit 70 40 10 20

(Millions of 2017 dollars)

Military Personnel per Unit 1,840 470 750 630

Annual Cost per Unit 440 190 100 140

(Millions of 2017 dollars)

Military Personnel per Unit 920 340 270 310

Annual Cost per Unit 160 50 40 70

(Millions of 2017 dollars)

Total Direct Overhead Indirect

MQ-1 “Predator” Squadron

RQ-4 “Global Hawk” Squadron

MQ-9 “Reaper” Squadron

18. For more information about such systems, see Congressional 

Budget Office, Policy Options for Unmanned Aircraft Systems

(June 2011), www.cbo.gov/publication/41448.
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Figure 4-5.

Aircraft and Personnel in Notional Air Force Unmanned Air System Squadrons

Source: Congressional Budget Office, using data from the Department of Defense.

All units presented here are notional squadrons of 12 aircraft (actual squadrons vary in size).

remote operator. Not all of those factors are inherent to 

unmanned systems; rather, they have resulted from the 

state of available technology and from specific choices 

about what capabilities the military needed during the 

past decade and a half—the span over which most of 

today’s drones were purchased.

If desired, it should be possible to design a drone with 

fewer of those disadvantages. However, improved capability almost always means higher cost. For example, current 

unmanned aircraft are generally less expensive than 

manned aircraft largely because their airframes were 

designed for fairly low-performance, undemanding flight; 

basically, they need to be able to carry a package of sensors (and, in many cases, a few weapons) to a target area 

and have enough fuel to loiter there for extended periods. 

They are not expected to have high speed and maneuverability, to carry heavy payloads, or to operate in defended 

airspace like many manned combat aircraft—characteristics that can significantly increase costs. Unmanned aircraft with those more advanced capabilities have been 

proposed, including an unmanned version of a new longrange bomber. But such advanced drones are not 

expected be low-cost aircraft.

In their current configuration, most of the Air Force’s 

unmanned aircraft are intended to operate mainly in 

undefended airspace and would generally not be capable 

of surviving engagements with modern air defenses. 

Thus, they would have limited utility in a high-intensity 

conventional conflict; they are most useful in lowintensity and unconventional conflicts, such as the occupations of Iraq and Afghanistan and counterterrorism 

missions.

According to publicly available accounts, drones have 

been very effective at attacking small numbers of targets 

in counterterrorism operations. However, their use by the 

United States to kill suspected terrorists has generated 

public controversy (in some cases because drone strikes 

have killed people other than the intended targets). In 

particular, the use of unmanned aircraft to attack targets 

in countries with which the United States is not at war 

(such as Pakistan) risks generating significant hostility to 

the United States in those countries. In addition, the strategic utility of targeted killings is not clear—many organizations are resilient enough to quickly replace leaders 

and other personnel who are killed, so occasionally eliminating members of an organization may not significantly 

MQ-1 “Predator” Aircraft

MQ-9 “Reaper” Aircraft

= 100 Personnel

0 100 300 400 500 feet 200

RQ-4 “Global Hawk” Aircraft 
102 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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reduce its long-term effectiveness. At the same time, 

however, the security measures that many terrorist groups 

appear to take to avoid drone strikes also degrade the 

groups’ effectiveness in various ways. For example, senior 

leaders who are in hiding cannot freely direct their subordinates because such communication puts them at risk 

of being detected and killed.19

Past and Planned Use. The United States has had small 

numbers of unmanned aircraft for many decades, but the 

widespread deployment of highly capable unmanned air 

systems is a fairly recent phenomenon. The MQ-1 and 

RQ-4 were developed in the 1990s and fielded in the 

2000s, and the MQ-9 was developed in the 2000s and 

fielded in the 2010s. Despite their recent introduction, 

those unmanned aircraft have been used heavily in recent 

operations, particularly in the war on terrorism and the 

occupations of Iraq and Afghanistan. Although efforts to 

arm unmanned surveillance aircraft began before the 

invasions of Afghanistan and Iraq, the current widespread 

practice of arming drones to attack ground targets 

appears to have evolved from their extensive use in those 

conflicts. Mounting weapons on an unmanned surveillance aircraft has proved to be particularly useful in counterinsurgency and counterterrorism operations because it 

has enabled DoD to attack small, mobile targets as soon 

as they are detected and identified without having to 

summon another aircraft to carry out the attack (such 

“fleeting” targets would often be lost before the strike 

aircraft could arrive). For missions requiring substantial 

firepower, however, the strike capacity offered by today’s 

drones, though useful, is minor compared with that of 

tactical aircraft or bombers.

For the immediate future, unmanned air systems will 

probably continue to be particularly useful in two types 

of situations. First, as part of U.S. counterterrorism operations, DoD is likely to remain responsible for monitoring 

many different theaters over a very large area for suspected 

terrorists, insurgents, and militants. Having access to 

large numbers of relatively low-cost and long-duration 

aerial sensors, such as those provided by unmanned aircraft, has proved extremely useful in that role. Second, in 

higher-intensity operations, the Air Force’s unmanned 

aircraft have the potential to increase the rate at which 

ground targets can be detected and identified. That 

potential, when combined with the increased capacity to 

strike targets that has resulted from the widespread adoption of precision-guided munitions (as described at the 

end of this chapter), could increase the rate at which 

targets can be destroyed. 

For the more distant future, the Air Force is likely to continue pursuing advances in the capabilities of drones, particularly their ability to face the advanced air defenses 

postulated in some of DoD’s planning scenarios. (The 

Navy is already grappling with that issue as it tries to field 

a drone that can operate from aircraft carriers. It faces a 

choice between a relatively inexpensive unmanned aircraft, akin to the Air Force’s MQ-9, that is optimized for 

surveillance and a more advanced system that is capable 

of penetrating advanced air defenses and conducting both 

surveillance and strike missions.) Unmanned aircraft may 

also be considered an option as the Air Force begins to 

define requirements for its next-generation air superiority 

aircraft, which is tentatively slated to be fielded in the 

2030s.

19. As an example, Mohammed Omar, former leader of the Taliban, 

was dead for two years before his death became widely known, 

even to some members of the Taliban itself. Possibly because of 

the threat of drone strikes, Omar had been secluded from contact 

with his organization (and the rest of the world) as a security 

measure. Such extreme seclusion prevents a leader from freely 

directing and controlling an organization.
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Major Element of the Force Structure

Other Department of the Air Force Units and Activities

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. Squadron of 50 Minuteman missiles.

b. In the analytic framework used for this report, other units and activities are generally considered to not have any units supporting them and thus to not 

have any indirect personnel or costs.

Although the majority of the Air Force’s units are connected with aircraft squadrons, the service includes a 

number of other units with special capabilities that are 

not directly related to aircraft squadrons. Together, those 

units account for 21 percent of the Department of the 

Air Force’s operation and support funding.

Minuteman III ballistic missiles armed with nuclear 

warheads are the Air Force’s land-based contribution to 

the U.S. nuclear deterrent (in addition to the air-based 

contribution provided by long-range bombers capable of 

carrying nuclear weapons). Land-based ballistic missiles 

are generally considered to have the fastest response time 

of any system for delivering nuclear weapons, and they 

are deployed in dispersed, hardened silos that would 

require an adversary to use a relatively large number of 

nuclear weapons to destroy the entire Minuteman force. 

Bombers, by contrast, can be vulnerable to air defenses, 

and ballistic missile submarines can be attacked by ships 

or other submarines before they launch their missiles or 

while they are in port. 

As with all strategic nuclear forces, the number of 

Minuteman missiles is generally determined by national 

nuclear policy and by the outcomes of arms control negotiations rather than by the considerations that typically 

apply to other military units. Such agreements can affect 

not only the number of ballistic missiles that the Air 

Force deploys but also the number of warheads on each 

Minuteman missile. The United States has an inventory 

of 450 deployed Minuteman III missiles, but current 

plans call for reducing that number to 400 by 2018 to 

comply with the New START treaty. 

Military Personnel per Unit 2,040 690 650 690

Annual Cost per Unit 380 130 90 160

(Millions of 2017 dollars)

Total Military Personnel 19,340 12,780 0 b 6,560

Total Annual Cost 2,170 660 0 b 1,520

(Millions of 2017 dollars)

Total Military Personnel 24,070 15,900 0 b 8,170

Total Annual Cost 3,730 1,840 0 b 1,890

(Millions of 2017 dollars)

Total Military Personnel 49,010 32,370 0 b 16,630

Total Annual Cost 10,000 6,160 0 b 3,840

(Millions of 2017 dollars)

Minuteman III Missile Squadrona

RED HORSE Construction Engineers

Air Force Special-Operations Forces

Rest of the Air Force

Total Direct Overhead Indirect
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Air Force construction engineers, known as RED 

HORSE (Rapid Engineer Deployable Heavy Operational 

Repair Squadron Engineers) squadrons, provide a variety 

of engineering services to the Air Force. In the past, they 

have contributed to the success of U.S. military operations in distant theaters by building or improving air 

bases in places with poor infrastructure and few basing 

options. Because the United States has often intervened 

in countries with limited infrastructure—and because the 

deployment of U.S. forces can place great demands on 

the ports and air bases that receive them—the ability to 

improve that infrastructure has typically been highly 

valuable, despite its relatively low visibility. The majority 

of RED HORSE personnel are in the Air Force’s reserve 

component.

The Air Force also maintains special-operations forces,

which are trained, equipped, and overseen by the 

Department of Defense’s Special Operations Command 

(SOCOM). They focus on such missions as unconventional 

warfare, special reconnaissance, counterterrorism, and the 

training of foreign militaries. The forces overseen by 

SOCOM are discussed in more detail in Chapter 5, 

which deals with defensewide activities.

By the Congressional Budget Office’s estimate, about 

49,000 military personnel and $10.0 billion a year are 

devoted to units and activities of the Department of 

the Air Force other than those described in this chapter. They include a variety of smaller organizations providing capabilities that are neither aircraft squadrons nor 

organized in support of aircraft squadrons. An important 

example is the Air Force’s space infrastructure, which 

includes the service’s constellations of Global Positioning 

System communications, weather, and missile-warning 

satellites. Other examples include the Air Force’s contributions to various joint commands and defensewide 

organizations, as well as some command-and-control and 

intelligence functions.
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Special Topic

The U.S. Military’s Strike Capability

Many of the military assets available to the Department 

of Defense can be thought of as almost generic tools able 

to attack and destroy a wide variety of enemy targets. 

That ability, called strike capability, is a marked departure 

from past practice. Previously, U.S. forces were more specialized in their ability to attack a given type of target, 

and that specialization often restricted their ability to perform more than a few specific types of missions. Today, 

the array of systems that exist to identify and destroy targets provides DoD with a unified strike capability that, 

in most conflicts, is limited more by the ability to gather 

information about hostile targets than by any other 

factor.

The full array of U.S. strike assets includes cruise missiles 

(Air Force and Navy); artillery, rockets, and attack helicopters (Army and Marine Corps); bombers (Air Force); 

fixed-wing tactical aircraft (Air Force, Navy, and Marine 

Corps); and armed unmanned air systems (Air Force and 

Army). To receive information about targets, those assets 

depend on a vast network of sensors and communications—everything from requests by infantry for fire 

support to imagery from satellites. The ability to gather 

information about potential targets and communicate it 

to versatile strike assets is at the heart of the current U.S. 

strike system—allowing military commanders to treat a 

theater of operations as essentially a single list of targets 

and a single list of assets available to destroy those targets. 

The two lists can be centrally managed by commanders 

to match the “supply” of strike assets with the “demand” 

of targets in a single system that will rapidly destroy all 

available targets.

The key developments that have produced the modern 

strike system have narrowed the differences not only 

between types of strike assets (particularly aircraft) but 

also between types of targets, thus greatly improving the 

capability of U.S. forces. As a result, in most recent conflicts, the United States has been able to destroy all 

known fixed infrastructure targets within the first few 

days of an operation. Subsequent attacks could then focus 

almost entirely on supporting ground forces, preventing 

previously destroyed targets from being rebuilt (“regenerated,” in technical parlance), and attacking new targets 

that were not identified earlier. All of those activities 

depend crucially on intelligence and surveillance, which 

is why U.S. strike capability today is often constrained 

more by the ability to gather intelligence than by the ability to deliver weapons.

Developments That Have Reduced the Differences 

Between Types of Strike Assets. The evolution of the 

strike system has been particularly dramatic in the case of 

aircraft, which provide the majority of U.S. strike capability. Historically, tactical aircraft and bombers faced 

extreme challenges in attacking targets on the ground. 

Broadly speaking, they needed to be able to operate in 

potentially hostile airspace, possibly far from friendly 

bases; locate targets that might be moving or obscured; 

and attack them with relatively inaccurate weapons. 

Those challenges led to the creation of highly specialized 

aircraft, capable of performing only a small range of tasks, 

as well as to highly specialized missions, reflecting the different problems involved in attacking different kinds of 

ground targets. As a result, there was little commonality 

between the sort of aircraft that could provide close air 

support (attacking hostile ground forces that were in contact with friendly ground forces) and the sort of aircraft 

that could perform strategic bombing (attacking enemy 

infrastructure or other fixed targets deep within a hostile 

state). 

For example, the A-10 attack aircraft was designed 

mainly to support U.S. ground forces by destroying 

enemy armored forces. Originally, its weaponry included 

antitank guided missiles and armor-penetrating cannons; 

it depended primarily on the pilot spotting targets visually; its airframe was developed to operate efficiently at 

relatively low altitudes and speeds; its range was fairly 

short; and its defenses included armor to protect its pilot 

from antiaircraft guns. The B-1 bomber, in contrast, was 

designed mainly to penetrate Soviet airspace in a nuclear 

attack. Originally, its weaponry included nuclear-armed 

cruise missiles and bombs; it received information about 

its targets before takeoff; its airframe was developed for 

efficient cruising, with limited low-altitude flight; its 

range was relatively long; and its defenses included complex jamming systems to foil attacks by radar-guided missiles. Neither aircraft could perform the other’s role, and 

the two would be treated very differently in operational 

usage. 
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In modern operations, however, both the A-10 and the 

B-1 can attack and efficiently destroy a wide variety of 

targets with conventional weapons, and they can substitute for each other in some circumstances. Although the 

two platforms still differ, with greater strengths in some 

specific roles, there is now substantial overlap in their 

capabilities and in the types of missions they can perform. Unlike the previous situation—in which the A-10 

fleet would have been irrelevant in a nuclear attack and 

the B-1 fleet would have been irrelevant in a defense 

against armored forces—both fleets can be used in most 

current conventional combat operations. Four primary 

developments have led to that convergence:

B The U.S. military’s recent ability to quickly achieve air 

supremacy in a conflict, which gives all strike aircraft a 

much better chance of surviving their missions; 

B The widespread use of tankers for aerial refueling, 

which greatly improves the range of all strike aircraft; 

B The development of better methods for spotting targets and communicating information about them, 

which greatly improves the ability of all strike aircraft 

to find their targets; and 

B The development of relatively affordable and accurate 

precision munitions, which greatly improves the ability of all strike aircraft to actually destroy their targets. 

Today, the major differences between the strike capabilities of most U.S. combat aircraft relate to their electronics 

and software rather than to traditional design factors such 

as range, speed, or payload capacity. Effective strike missions require aircraft that are capable of accepting up-todate information about a target from a wide range of 

sources, carrying the most modern munitions, and communicating targeting information to those munitions. 

Such aircraft, if properly supported, can effectively attack 

almost any ground target in a modern conflict.

Although the developments listed above have had the 

greatest consequences for aircraft, most of them have 

affected other strike assets as well. For instance, the 

Army’s and Marine Corps’ attack helicopters have benefitted from almost all of those developments in much the 

same way that fixed-wing aircraft have. In addition, the 

Army’s artillery is vastly more capable when equipped 

with affordable and accurate munitions that are provided 

with high-quality targeting data.

DoD and many outside observers have cautioned that the 

freedom U.S. forces have had to strike targets in recent 

conflicts might not exist in future conflicts against more 

competent or well-armed opponents. The effectiveness 

of the U.S. strike system depends on several factors that 

opponents could disrupt. As examples, an effective 

method of jamming Global Positioning System (GPS) 

signals could degrade the effectiveness of U.S. munitions, 

and the loss of air superiority could imperil strike aircraft 

and greatly limit the use of aerial refueling. 

Developments That Have Reduced the Differences 

Between Types of Targets. Before the creation of 

cheaper and more accurate munitions that could receive 

targeting information from many sources, the limitations 

of sensors and weapons meant that attacking different 

types of targets required very different approaches. 

Whether a target was mobile or stationary, situated close 

to friendly forces or not, and heavily armored or not were 

all crucial factors in determining how challenging the target would be to destroy and how it would be attacked.

Traditional unguided bombs (now often referred to as 

“dumb” bombs) were notoriously difficult to hit targets 

with. As a result, attacking a fixed target generally 

required having several aircraft drop large loads of bombs 

to increase the chances of a close hit—and even then, 

multiple attacks were frequently necessary before a target 

was destroyed. Mobile targets were often impossible to 

destroy with any certainty in such a manner, armored 

targets (even when stationary) could not reliably be hit 

closely enough to penetrate their armor, and the inaccuracy of weapons led to sharp restrictions on using them in 

proximity to friendly ground forces and noncombatants. 

Previous U.S. efforts to improve munitions frequently 

focused on developing specialized warheads and sensors 

that could attack a specific type of target more effectively, 

but in many cases they were too expensive to field in large 

numbers. 

Many modern precision munitions incorporate specialized sensors, such as radar or infrared guidance systems, 

but they are notable for their heavy reliance on GPS guidance sets, which are cheaper than other types of guidance 

systems. By itself, GPS guidance is usually accurate 

enough for attacks on stationary targets, and munitions 

with other sensors are usually accurate enough for attacks
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on mobile targets.20 Crucially, the ability to accept GPS 

targeting data from other sources means that any strike 

asset equipped with such munitions, connected to 

communications networks, and able to pass target coordinates to the munitions can effectively attack the target. 

For example, a U.S. bomber pilot need not see enemy 

infantry in contact with U.S. ground forces to engage 

that enemy; instead, the bomber can receive targeting 

data from the U.S. ground forces and attack the target 

they have identified.

When provided with accurate targeting data, such modern munitions are precise enough that a single bomb has 

a good chance of destroying most types of ground targets. 

That ability in turn allows a single aircraft to destroy 

many targets, rather than requiring several aircraft to 

destroy a single target—an enormous increase in U.S. 

strike capability.

20. GPS guidance tends to be equally effective regardless of the type 

of target being attacked because munitions equipped with that 

guidance move toward a specific set of physical coordinates; if the 

target is at those coordinates, the munition will generally strike it. 

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CHAPTER

5

Defensewide Activities

Overview

The Department of Defense contains a number of organizations that are not part of the Departments of the 

Army, Navy, or Air Force. Instead, those defensewide 

organizations perform activities that support DoD as a 

whole. Such organizations employ some military personnel, but they do not directly fund those personnel, 

because all military personnel are part of one of the services.1

 However, they do employ and fund DoD civilian 

personnel—about 216,000, on average, over the 2017–

2021 period, according to the DoD’s budget plans.

Defensewide organizations fall into three broad 

categories: 

B Organizations that make up DoD’s highest levels of 

command and control—the Office of the Secretary 

of Defense, the Joint Staff (a headquarters staff at the 

Pentagon composed of personnel from all of the services that assists the Chairman of the Joint Chiefs of 

Staff), and the regional combatant commands (groups 

of personnel from multiple services that are responsible for U.S. military strategy in specific geographic 

areas, such as U.S. Africa Command and U.S. Pacific 

Command). 

B Organizations that provide specialized military capabilities that are not specific to any one service—

examples include Special Operations Command, the 

Missile Defense Agency, and the military intelligence 

agencies. 

B Organizations that give administrative support to all 

of DoD—most notably, the Defense Health Program 

(DHP), which provides health care to service members, retired military personnel, and their dependents. 

Other such organizations operate schools for military 

dependents, run commissaries and exchanges (stores 

for military families), take care of payroll and finance 

activities, and provide telecommunications and logistics services. This category accounts for the largest 

share of defensewide operation and support (O&S) 

funding, 

For this analysis, the Congressional Budget Office largely 

combined the first two categories of defensewide organizations. Most information about military intelligence 

activities is classified, so CBO could not describe their 

portion of DoD’s budget in any detail.2

 The only organization from the first two categories whose budget CBO 

treated separately, for visibility, was Special Operations 

Command. All of the other organizations in those two 

categories were included either in the group “Classified 

Defensewide Funding” or in the group “Rest of the 

Defensewide Organizations.”

For the third category, CBO distributed the costs of organizations that provide administrative support for DoD as 

a whole to the various units that generate the workload 

for those organizations. For example, CBO assigned the 

largest single defensewide cost—that of the Defense 

Health Program—to major combat units according to 

their numbers of active- and reserve-component personnel and their respective costs. Thus, the costs shown in 

the previous chapters for a major combat unit (or its support units or overhead activities) include that unit’s portion of DHP costs. The DHP also funds health care for 

retired military personnel and their dependents, but 

CBO did not distribute that portion of the program’s 1. Military personnel who work in defensewide activities, such as 

members of the Joint Staff and combatant commanders, are 

funded by the military service to which they belong. When service 

members are assigned to a defensewide activity, the activity tracks 

the costs incurred for those personnel through a system of DoD 

internal accounting credits that show the amounts that the military services must contribute to defensewide personnel costs.

2. DoD provides some insight into the classified portion of defensewide O&S spending in its publicly available budget materials, but 

that information relates only to the year for which the budget 

request is being made, not to the full five years covered in DoD’s 

budget documents.
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funding among units because it is not a cost of maintaining current units. Instead, that part of DHP funding is 

shown in a separate entry in this chapter.

Since the late 1970s, the share of its funding that DoD 

devotes to defensewide activities has been growing—not 

necessarily because the department is providing greater 

amounts of support (although in some cases, such as 

health care, it is) but generally because DoD is becoming 

a more fully integrated institution over time. Many of the 

functions now carried out by defensewide agencies were 

formerly performed by the individual services but have 

gradually been centralized. That trend is generally seen 

as positive and as especially appropriate for joint installations and activities. (There is no reason, for example, to 

believe that the Air Force is particularly well suited to 

operating commissaries for Air Force personnel in a way 

that another, more focused, organization would not be.)

One consequence of the growing share of funding 

devoted to defensewide activities is that the costs that a 

military department bears for sustaining its units do not 

reflect the full cost of those units because defensewide 

agencies incur some of those costs. Thus, simply looking 

at the Army’s cost to sustain an infantry brigade combat 

team—without including the defensewide costs associated with such things as processing the unit’s payroll, 

educating its dependents, or providing commissaries for 

its personnel—will understate the unit’s true costs. 

CBO included such defensewide support as part of the 

cost of every unit, so the total cost of a military department’s units in this analysis reflects those additional costs. 

As a result, the total cost that CBO attributes to the 

Army, for example, to sustain all of its units exceeds the 

Army’s total O&S budget, whereas the amount of purely 

defensewide costs not attributed to any military department is much smaller than the defensewide O&S budget.

The rest of this chapter presents CBO’s analysis of the 

following major defensewide activities:

B Special operations; see page 111.

B The Defense Health Program; see page 114.

B All of the other units and activities that support DoD 

as a whole, presented together; see page 116.

This chapter also examines two topics of special concern 

to the Department of Defense: 

B The structure of the U.S. military’s nuclear forces; see 

page 117.

B The United States’ missile defense capability; see 

page 120.
CHAPTER 5: DEFENSEWIDE ACTIVITIES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 111

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Major Element of the Force Structure

Special Operations

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. In the analytic framework used for this report, special-operations units are considered to not have any units supporting them and thus to not have any 

indirect personnel or costs.

b. Funding for the services’ special-operations units comes from each service’s budget, so these numbers appeared in previous chapters in the entries 

for “Other Units and Activities.” They are repeated here to provide a complete picture of the costs of the U.S. military’s special-operations forces.

c. Funding for Special Operations Command (SOCOM) comes from the defensewide operation and maintenance budget. Like other defensewide 

organizations, SOCOM does not directly fund any military personnel of its own (because all military personnel are part of one of the services). No 

overhead costs are shown for SOCOM because such costs are apportioned on the basis of the number of military personnel in an activity.

The Department of Defense has traditionally distinguished between “special forces” (SF) and “specialoperations forces” (SOF). Special forces are a fairly small 

set of units that perform direct-action missions (small, 

short-duration raids, ambushes, or assaults in hostile territory, such as the raid on Osama bin Laden’s compound 

in Pakistan). SF units include the units most commonly 

associated in the public’s mind with special operations, 

such as the Army’s Green Berets and Rangers and the 

Navy’s Sea, Air, and Land forces (known as SEALs). 

Special-operations forces encompass a larger set of units 

that include not only SF units but also personnel responsible for psychological operations, civil affairs, and other 

specialized activities, all of which are overseen by Special 

Operations Command (SOCOM)—the organization 

within DoD responsible for special-operations forces.

Total Military Personnel 45,100 32,370 0 12,730

Total Annual Cost 7,210 3,190 0 4,020

(Millions of 2017 dollars)

Total Military Personnel 16,440 9,900 0 6,550

Total Annual Cost 2,370 1,050 0 1,330

(Millions of 2017 dollars)

Total Military Personnel 3,530 2,130 0 1,410

Total Annual Cost 490 210 0 280

(Millions of 2017 dollars)

Total Military Personnel 24,070 15,900 0 8,170

Total Annual Cost 3,730 1,840 0 1,890

(Millions of 2017 dollars)

Total Military Personnel 0 0 0 0

Total Annual Cost 5,370 5,370 0 0

(Millions of 2017 dollars)

Total Direct Overhead Indirecta

Army Special-Operations Forcesb

Navy Special-Operations Forcesb

Marine Corps Special-Operations Forcesb

Air Force Special-Operations Forcesb

Special Operations Commandc
112 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Each military service recruits personnel for its specialoperations units, provides their initial training, and pays 

their salaries. SOCOM provides those units with specialized training and equipment. SOCOM also develops 

doctrine and strategy for special-operations units and is 

responsible for ensuring that all U.S. special-operations 

forces can be used in a unified way by a combatant commander (as opposed to having separate special-operations 

communities in each service that operate in their own 

ways and focus on their own limited missions). 

Current and Planned Structure. DoD’s specialoperations forces consist of a broad array of diverse units. 

In all, the department plans to field an average of about 

60,000 special-operations direct personnel over the 

2017–2021 period.

Purpose and Limitations. SOF are intended to be 

versatile forces, capable of conducting a wide range of 

missions, including those that other military units would 

not be suited for. Among their multiple roles, the most 

important are considered to be direct action, special 

reconnaissance, foreign internal defense, and securityforce assistance. The last two activities involve helping 

friendly governments improve their military capabilities 

(often in order to defeat insurgencies hostile to the 

United States); those missions generally require the 

largest commitments of SOF personnel and time. Thus, 

special-operations forces could be described as an exceptionally well-trained and well-equipped set of trainers for 

foreign militaries—capable, when needed, of performing 

combat roles as well.

SOF have numerous limits on their use, which relate to 

the extremely difficult missions they are often assigned. 

For example, direct-action missions generally require very 

good intelligence, as well as a situation in which a small 

force, operating with the benefit of surprise, can achieve a 

highly valuable objective. Even so, direct-action missions 

have a mixed record of success—SOCOM was created in 

the 1980s largely in response to the failure of special 

forces to rescue U.S. hostages in Iran. Where the conditions for direct action are not present, SF can function as 

highly trained light infantry, although that role is often 

considered a waste because it does not capitalize on the 

unique capabilities of special forces. That role has also 

been associated with poor outcomes on some occasions, 

such as in Mogadishu, Somalia, in 1993 (when what was 

supposed to be a short raid turned into an overnight 

confrontation with local militiamen that resulted in 

many SF casualties) and in Tora Bora, Afghanistan, in 

2001 (when SF personnel failed in an attempt to capture 

Osama bin Laden).

When special-operations forces are performing their 

more common role of training foreign militaries, their 

effectiveness is limited by their host countries’ willingness 

and ability to make use of that training. In general, it is 

difficult to assess how well a foreign country would combat an insurgency with or without the assistance of 

U.S. special-operations forces. Insurgencies are generally 

ended not through military force but through negotiated 

settlements; however, having a strong military often helps 

a government persuade insurgents to negotiate and 

strengthens the government’s position during the negotiations. Another limitation associated with using SOF is 

that because they often assist countries that have relatively 

unstable or unpopular governments, their work risks 

associating the United States with the actions of those 

countries’ militaries, as happened in El Salvador in the 

1980s. 

Past and Planned Use. Many of the missions for which 

special-operations forces are intended—as well as many 

of their past and current operations—are classified. A 

common complaint of both the SOF and intelligence 

communities is that because of the classified nature of 

their work, their failures are more visible than their successes, giving the public a distorted view of their value.

SOF have participated in all major U.S. combat operations since SOCOM was created. In most cases, their 

participation was not central to the outcome of those 

combat operations (largely because their role was limited 

to providing reconnaissance or carrying out small missions within the larger operation). However, in Operation 

Enduring Freedom in Afghanistan, SOF units played a 

leading role in the initial phases of ground combat by 

assisting Afghan rebel forces by calling in air strikes; conventional U.S. ground forces arrived only after the 

Taliban had lost control of much of the country. Since 

the invasion, SOF have been used extensively in and 

around Afghanistan, achieving a notable success with 

the direct-action mission of killing Osama bin Laden but 

experiencing more mixed results when employed as light 

infantry (as at Tora Bora).

SOF have also been widely used for activities other 

than major combat operations. Some of the largest 

commitments of U.S. special-operations forces for 
CHAPTER 5: DEFENSEWIDE ACTIVITIES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 113

CBO

foreign internal defense and security-force assistance have 

occurred in El Salvador, Colombia, Iraq, Afghanistan, the 

Philippines, and, more recently, the Horn of Africa and 

Trans-Saharan Africa. None of the foreign governments 

that received such assistance have been militarily overthrown by insurgents or terrorists, although some remain 

unstable. However, the government of Mali was overthrown by members of the country’s military twice since 

U.S. assistance began, weakening the government in its 

fight against insurgents and exposing the United States to 

criticism about the effectiveness of its training. Some 

SOF commitments have also opened the United States to 

criticism because of the actions of the foreign militaries it 

has assisted (particularly those in Latin America). 

SOCOM and other DoD sources frequently describe 

special-operations forces as crucial for antiterrorism missions. In essence, such missions are the same as traditional 

SOF missions except that the adversaries are terrorist 

groups rather than insurgents or other countries’ militaries. Many of the SOF operations in countries mentioned 

above were antiterrorist missions. Special-operations 

forces have also participated in a wide variety of smaller 

missions, such as helping to evacuate noncombatants 

during a crisis or providing humanitarian assistance or 

disaster relief.
114 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Defense Health Program

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest $10 million; more detailed information is presented in Appendixes A 

and B.

Defensewide organizations do not directly fund any military personnel of their own (because all military personnel are part of one of the services). In 

addition, in the analytic framework used for this report, defensewide organizations are considered to not have any units supporting them and thus to not 

have any indirect personnel or costs. No overhead costs are shown for the defensewide organizations because such costs are apportioned on the basis 

of the number of military personnel in an activity.

The Department of Defense offers medical and dental 

care to more than 9 million service members, military 

retirees, and eligible family members through the Military Health System (MHS) at an estimated cost of about 

$47 billion in 2016.3

 The MHS exists to ensure that service members are fit for deployment and to care for them 

if they are sick, injured, or wounded. The system also 

provides care for military families and retirees.

Current and Planned Structure. The cost of the MHS is 

accounted for in three major blocks of DoD’s budget:

B The Defense Health Program—a defensewide activity 

that pays for nearly all of the civilian personnel associated with the MHS, as well as for contracts for private-sector care and purchases of medical supplies.4

B Funding for MHS military personnel—including the 

pay of service members associated with the MHS, 

which is funded by their military departments. 

(Together, those first two blocks make up the 

TRICARE system, which is responsible for providing 

care to active-duty service members and their families 

and military retirees and their families.) 

B Accrual charges levied against the services for all military 

personnel—funds deducted from military personnel 

appropriations and credited to the Medicare-Eligible 

Retiree Health Care Fund, which reimburses military 

medical facilities for care provided to Medicare-eligible 

retirees and their family members and also covers most 

of the out-of-pocket costs of Medicare-eligible retirees 

and their family members who seek care from privatesector Medicare providers.

Although the Defense Health Program is the only portion of the Military Health System whose costs are 

included in the defensewide budget, the discussion 

below focuses on the MHS as a whole.

In the Congressional Budget Office’s analysis, the system’s 

costs for current service members and their families are 

included in the costs of the various elements of the force 

structure discussed in previous chapters, allocated in proportion to the number of military personnel employed by 

those elements. The $14.7 billion shown here covers only 

health care for military retirees and their families. CBO 

did not divide that cost among various elements of the 

force structure because it is not a cost of current forces 

and it cannot be altered by decisions about the future 

force structure. Instead, that cost results from prior decisions about the force structure that produced the current 

pool of retirees and from the policies and laws that govern 

health care benefits for military retirees. Lawmakers could 

change those laws, but in the past, they have been 

extremely reluctant to do so. 

Total Military Personnel 0 0 0 0

Total Annual Cost 14,720 14,720 0 0

(Millions of 2017 dollars)

Total Direct Indirect Overhead

Defense Health Program for Retirees

3. See Congressional Budget Office, Long-Term Implications of the 

2016 Future Years Defense Program (January 2016), pp. 22–25, 

www.cbo.gov/publication/51050. 

4. For a fuller discussion of the MHS, see Congressional Budget 

Office, Approaches to Reducing Federal Spending on Military Health 

Care (January 2014), www.cbo.gov/publication/44993.
CHAPTER 5: DEFENSEWIDE ACTIVITIES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 115

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The MHS is separate from the health care system operated by the Department of Veterans Affairs (VA), which 

has its own funding. VA provides health care to veterans 

who have service-connected disabilities or who meet certain other criteria. (It also provides cash payments that 

compensate for service-connected disabilities and GI Bill 

benefits that reimburse some of the costs of higher education for veterans.) The Military Health System is available to the roughly 2 million people who served long 

enough to retire from the military—typically for at least 

20 years—and to their eligible family members. VA benefits, by contrast, are potentially available to the 22 million 

veterans who received honorable or general discharges 

from the military, regardless of whether they served long 

enough to retire. Therefore, military retirees may be eligible for VA health benefits, but veterans who did not serve 

long enough to retire from the military are not eligible for 

MHS benefits after they leave the service.

Purpose and Limitations. Providing health care is 

considered an important military function for several 

reasons:

B It cares for personnel who are involved in ongoing 

military operations.

B It represents a substantial portion of the total compensation package that military personnel receive and is 

thus important for recruiting and retaining service 

members. 

B It plays a key role in maintaining the readiness of units 

by making sure that military personnel are healthy. 

B It helps lessen some of the challenges of military life 

because service members can generally be assured of 

receiving quality medical care for themselves and their 

families even when they are deployed for an operation 

or stationed in a foreign country. 

B It is widely seen as a moral duty to care for people who 

may risk their lives while serving their country.

The MHS accounts for a large portion of DoD’s budget—about a quarter of the total operation and support 

budget—and has been growing rapidly in recent years.5

Past analyses by CBO indicate that much of that cost 

growth has occurred for two reasons: Military retirees are 

increasingly choosing to use MHS services rather than to 

rely on health insurance provided by a subsequent 

employer (or their spouse’s employer), and MHS beneficiaries generally use medical care at relatively high rates. 

Those beneficiaries face very low premiums or copayments for their care, and people tend to use a service 

more when they pay less for it themselves. As a result, 

DoD takes in fairly small revenues from MHS beneficiaries while experiencing the high costs that stem from their 

intensive use of care. DoD has put forward a number of 

proposals in recent years to increase the amount of cost 

sharing for MHS beneficiaries in an effort to reduce the 

costs of the system. So far, however, lawmakers have not 

been receptive to such proposals.6

Past and Planned Use. The vast majority of the MHS’s 

workload results from providing health care to service 

members, retirees, and their eligible family members during peacetime. That workload is not expected to change 

appreciably anytime soon. 

The MHS also provides health care for personnel who are 

involved in ongoing military operations, and it is likely to 

keep doing so as long as such operations include any risk 

of casualties.7

 Although that role is important, it requires 

less funding and creates less workload than the peacetime 

provision of health care.8

 The main reason is that 

deployed service members make up only a small portion 

of the system’s total beneficiaries—not all service members are deployed at a given time, and family members 

and retirees are not deployed. In addition, the MHS 

often takes part in humanitarian missions of various sorts, 

such as providing medical assistance in the aftermath of 

natural disasters.

5. See Figure 2-3 in Congressional Budget Office, Long-Term 

Implications of the 2016 Future Years Defense Program

(January 2016), p. 24, www.cbo.gov/publication/51050.

6. For a brief legislative history of such cost-sharing proposals, see 

Congressional Budget Office, Costs of Military Pay and Benefits in 

the Defense Budget (November 2012), Appendix C, www.cbo.gov/

publication/43574.

7. Even operations that do not involve combat generate a need for 

medical care. Casualties include diseases and nonbattle injuries, 

which in many cases require more medical attention than battle 

injuries (even during active combat operations).

8. For more discussion of the effects of recent combat operations, see 

Congressional Budget Office, Approaches to Reducing Federal 

Spending on Military Health Care (January 2014), pp. 16–19, 

www.cbo.gov/publication/44993.
116 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Major Element of the Force Structure

Other Defensewide Units and Activities

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest $10 million; more detailed information is presented in Appendixes A 

and B.

Defensewide organizations do not directly fund any military personnel of their own (because all military personnel are part of one of the services). In 

addition, in the analytic framework used for this report, defensewide organizations are considered to not have any units supporting them and thus to not 

have any indirect personnel or costs. No overhead costs are shown for the defensewide organizations because such costs are apportioned on the basis 

of the number of military personnel in an activity

The Department of Defense includes a wide variety of 

other defensewide activities and organizations. A significant portion of their funding is classified, however, which 

prevents the Congressional Budget Office from providing 

any detail other than the amount of classified operation 

and maintenance funding that DoD discloses in its publicly available budget documents.9

 (Operation and maintenance funding is a subset of operation and support 

funding.)

The rest of the defensewide organizations, which represent a relatively small amount of DoD’s O&S budget, fall 

into two groups:

B High-level command-and-control functions, such as 

the Office of the Secretary of Defense, the Joint Staff, 

and the combatant commands. Although they are 

fairly small, those organizations include civilian and 

military personnel from multiple military departments 

and have responsibilities that affect significant portions of DoD’s mission.

B Miscellaneous activities that cannot be characterized 

as supporting any major combat units (and thus were 

not included in the costs for those units). Such activities include the Defense POW/MIA Office, which 

works to help U.S. prisoners of war and to locate personnel missing in action; the Defense Security Cooperation Agency, which works with foreign countries’ 

militaries and oversees military aid and arms sales to 

other nations; and the Office of Economic Adjustment, which helps state and local governments deal 

with the economic consequences of cutbacks in 

defense industries or closures or expansions of 

military bases.

Total Military Personnel 0 0 0 0

Total Annual Cost 14,540 14,540 0 0

(Millions of 2017 dollars)

Total Military Personnel 0 0 0 0

Total Annual Cost 4,060 4,060 0 0

(Millions of 2017 dollars)

Total Direct Indirect Overhead

Classified Defensewide Funding

Rest of the Defensewide Organizations

9. DoD’s O-1 budget display presents the full amount of classified 

operation and maintenance funding for each military department 

and for defensewide activities, but only for a limited number of 

years and with no breakdown between intelligence and other classified activities or other details. See Office of the Under Secretary 

of Defense (Comptroller), Department of Defense Budget, Fiscal 

Year 2017: Operation and Maintenance Programs (O-1), Revolving 

and Management Funds (RF-1) (February 2016), http://

comptroller.defense.gov/BudgetMaterials.aspx.
CHAPTER 5: DEFENSEWIDE ACTIVITIES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 117

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Special Topic

Nuclear Forces

Funding for the services’ nuclear forces comes from each service’s budget, so these numbers appeared in previous chapters in the entries for “Other 

Units and Activities” or “Bomber Squadrons.” They are repeated here to provide a complete picture of the costs of the U.S. military’s nuclear forces. For 

additional details, see Congressional Budget Office, Projected Costs of U.S. Nuclear Forces, 2015 to 2024 (January 2015), www.cbo.gov/publication/

49870.

“Direct” personnel and costs are associated with a major combat unit, “indirect” personnel and costs are associated with units that support the major 

combat unit, and “overhead” personnel and costs are associated with the major combat unit’s share of administrative or overhead activities. For more 

information, see Chapter 1. The numbers shown here are rounded to the nearest 10 personnel or $10 million; more detailed information is presented in 

Appendixes A and B.

a. Squadron of 50 Minuteman missiles.

b. Notional squadron of 12 aircraft (actual squadrons vary in size).

The U.S. strategic nuclear force has traditionally been 

seen as a triad consisting of land-based intercontinental 

ballistic missiles (ICBMs), sea-based ballistic missile submarines (SSBNs), and airborne bomber aircraft. All of 

those platforms are capable of delivering nuclear weapons 

over long distances.

Current and Planned Structure. As part of the nuclear 

force structure, the Navy plans to field 14 SSBNs and 

4 guided missile submarines (SSGNs) in 2017.10 It 

does not expect to change those numbers through 2021 

(although the Department of Defense plans to reduce 

the number of active missile launch tubes on each SSBN 

from 20 to 16 by 2018 to comply with the New START 

arms control treaty). The Air Force intends to field 

450 Minuteman III ICBMs in 2017, but current plans 

call for it to reduce that number to 400 by 2018 to comply with the New START treaty. The Air Force’s B-52 

and B-2 bombers are also capable of delivering nuclear 

weapons, but unlike SSBNs and ICBMs, they spend 

most of their time performing their conventional (nonnuclear) role. DoD plans to remove the ability of some 

B-52s to deliver nuclear weapons by 2018 to comply with 

Military Personnel per Unit 660 320 80 260

Annual Cost per Unit 170 70 40 50

(Millions of 2017 dollars)

Military Personnel per Unit 2,040 690 650 690

Annual Cost per Unit 380 130 90 160

(Millions of 2017 dollars)

Military Personnel per Unit 3,830 1,310 1,220 1,300

Annual Cost per Unit 740 270 170 300

(Millions of 2017 dollars)

Military Personnel per Unit 8,660 2,120 3,600 2,940

Annual Cost per Unit 1,840 670 490 680

(Millions of 2017 dollars)

Ballistic and Guided Missile Submarines

Minuteman III Missile Squadrona

B-52 Bomber Aircraft Squadronb

B-2 Bomber Aircraft Squadronb

Total Direct Overhead Indirect

10. The Navy’s budget documents group the 14 SSBNs with the 

4 SSGNs, which are former SSBNs that have been converted 

to launch Tomahawk cruise missiles and to support special 

operations. 
118 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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the New START treaty.11 The nuclear warheads that missiles are armed with are funded mainly through Department of Energy accounts, which are not included in this 

analysis.

For the past 40 years, the U.S. nuclear force structure has 

been affected by the outcomes of arms control negotiations (although the United States always has the option to 

change its nuclear force structure unilaterally and has 

sometimes done so).12 The most recent arms control 

agreement, the New START treaty, has been in effect 

since 2011 and limits the total numbers of deployed 

strategic missiles and bombers (700), deployed strategic 

nuclear warheads (1,550), and deployed and nondeployed strategic missile launchers and bombers (800). 

The United States currently exceeds those limits, but it 

has until 2018 to comply with the treaty.

Purpose and Limitations. In practice, the fundamental 

role of U.S. nuclear forces is to deter any nuclear attack 

on the United States, its allies, or its partners through the 

threat of a devastating counterattack. However, at various 

points in history, U.S. policymakers have also considered 

the possibility of using nuclear forces to initiate an attack 

on a hostile state, to deter nonnuclear attacks on the 

United States, or to deter nonnuclear attacks on U.S. 

allies. (In particular, much debate during the Cold War 

focused on whether nuclear weapons could deter a 

possible Soviet invasion of Western Europe.)

As a deterrent, nuclear forces are intended to allow the 

United States to retaliate with so much firepower that no 

rational enemy could possibly view a nuclear attack on 

the United States as a reasonable option. Deterrence is a 

theoretical approach for understanding the decisionmaking process of opponents, and there are several variations on the core theory. However, almost all of them 

agree that successful deterrence requires a credible commitment and capability to respond with overwhelming 

force to any nuclear attack. Some variations on the theory 

would add that there are no uses for nuclear forces other 

than deterrence—which suggests that the purpose of 

nuclear weapons is to not be used. If U.S. decisionmakers 

agree with such views, the main limitation of nuclear 

forces is that their only role is to provide a credible deterrent. Another limitation is that some nuclear-armed 

opponents might not be rational actors and thus might 

not be deterred by U.S. nuclear forces.13 Finally, the use 

of nuclear weapons is limited by the fact that such use is 

considered by many people to be unacceptable in most 

circumstances.

Each part (or “leg”) of the nuclear triad has unique 

strengths and weaknesses that complement those of the 

other legs, such that the full triad is generally considered 

much more powerful than a “pure” deterrent composed 

of only one type of system. Historically, most of the value 

of the triad lay in discouraging the Soviet Union from 

launching a nuclear first strike on the United States that 

would have destroyed the U.S. capability to respond with 

a second strike. In the present era, concerns about deterrence often focus more on smaller nuclear powers (such as 

North Korea) that have less sophisticated arsenals for 

delivering nuclear weapons. Those smaller powers cannot 

credibly threaten a first strike that would destroy the U.S. 

capability to respond. However, all recent U.S. nuclear 

policy statements have indicated a commitment to maintaining the full triad. Because each leg of the triad is 

aging, DoD has modernization programs in place for 

all three.

U.S. ICBMs and SSBN-launched missiles are armed only 

with nuclear warheads and cannot be used for any nonnuclear purpose. (Although DoD has considered arming 

those missiles with conventional warheads, it has not 

done so.) The bomber fleet, by contrast, has routinely 

been used in major conflicts to deliver conventional 

weapons. During the Cold War, bombers were seen 

mainly as a nuclear delivery platform, and the majority 

of the bomber fleet was usually on some form of standby, 

able to launch quickly in case it was needed to carry out 

nuclear strikes. In the post–Cold War era, bombers have 

11. DoD also deploys short-range, smaller-yield nuclear weapons, 

known as tactical nuclear weapons. During the Cold War, all three 

military departments deployed such weapons, which numbered 

more than 10,000. They included bombs delivered by aircraft, 

artillery shells, torpedoes, land mines, sea-launched cruise missiles, 

and short-range surface-to-surface ballistic missiles. Today, only 

the Air Force deploys tactical nuclear weapons—bombs delivered 

by tactical aircraft. Those forces are not discussed here.

12. Recent arms control treaties have given the parties flexibility in 

meeting their obligations by specifying the total number of 

warheads or delivery systems allowed but letting each nation 

determine the mix of ICBMs, SSBNs, and bombers fielded.

13. That possibility is frequently raised in discussions of North Korea’s 

and Iran’s nuclear programs, as well as in hypothetical cases in 

which a terrorist group obtains a nuclear weapon.
CHAPTER 5: DEFENSEWIDE ACTIVITIES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 119

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been used extensively for conventional strikes, although 

the B-2 fleet and part of the B-52 fleet still routinely train 

for nuclear missions.

Past and Planned Use. The United States used two 

nuclear weapons against Japan in World War II but has 

not employed any nuclear weapons in combat since then. 

No other country has used nuclear weapons in combat. 

Supporters of the theory of deterrence point to the lack 

of nuclear exchanges as evidence that nuclear deterrence 

has been extremely successful. Nevertheless, as with all 

counterfactual examples, there is no way to prove that the 

U.S. nuclear deterrent was directly responsible for preventing a nuclear attack by the Soviet Union during the 

Cold War.
120 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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Special Topic

Missile Defense

The United States is currently operating a number of 

systems to protect itself and its allies from missile strikes. 

Those systems are generally developed and purchased by 

the Missile Defense Agency (MDA), and their acquisition 

costs are paid through the defensewide portion of the 

Department of Defense’s budget. Once purchased, however, missile defense systems are operated by the services, 

and most of their operation and support (O&S) costs are 

included in the budgets of the relevant military departments. In this report, all of a department’s O&S costs 

for missile defense are included in its chapter’s entry for 

“Other Units and Activities” (under “rest of” the 

department).

Several missile defense systems do not significantly add to 

their service’s O&S costs. For example, the Army fields 

Patriot missile battalions as part of its normal air-defense 

force structure, and the Navy fields Aegis cruisers and 

destroyers as part of its normal surface combatant fleet. 

Equipping those battalions and ships with advanced missiles capable of performing missile defense does not result 

in substantial new O&S costs to the Army or the Navy 

because those units existed already. If, in the future, missile defense missions caused more Patriot units to be created or more ships to be purchased, those forces’ O&S 

costs might be more directly attributable to missile 

defense. 

Other missile defense systems, such as the Ground-Based 

Midcourse Defense system and the Terminal High Altitude Area Defense system, incur additional O&S costs. 

However, those costs are very small compared with the 

costs of other elements of the force structure. 

Current and Planned Structure. DoD has four major 

missile defense systems, which are designed to intercept 

threatening missiles in midair:

B The Ground-Based Midcourse Defense (GMD) 

system, which the Army operates from various land 

bases (primarily Fort Greely, Alaska), is designed to 

protect the United States against long-range ballistic 

missiles. That system is intended to intercept missiles 

during the midcourse part of their flight (the phase 

after a missile’s rocket motor has stopped burning and 

accelerating the missile but before air resistance from 

reentry into the atmosphere has begun decelerating it). 

In that phase, missiles are at their maximum speed and 

are generally following predictable, parabolic paths.

B The Aegis Ballistic Missile Defense (BMD) system, a 

midcourse-phase interception system operated by the 

Navy from cruisers and destroyers, is designed to 

protect allies and U.S. forces from medium- and 

intermediate-range ballistic missiles.14 DoD is developing a land-based variant of the Aegis system, as well 

as an interceptor capable of targeting missiles during 

the terminal phase of their flight (when air resistance 

from reentry has begun decelerating them). Missiles in 

that phase are very close to their targets, which greatly 

reduces the time that missile defense systems have 

to react to them but also allows the use of relatively 

short-range and lower-cost interceptor missiles.

B The Terminal High Altitude Area Defense (THAAD) 

system, a terminal-phase interception system operated 

by the Army from mobile launchers, is designed to 

intercept short- and medium-range ballistic missiles as 

they near their targets.

B The Patriot Advanced Capability 3 (PAC-3) system, a 

terminal-phase interception system operated by the 

Army from mobile launchers, is similar to THAAD 

but is better suited to intercepting smaller short-range 

ballistic missiles. It can also intercept cruise missiles 

and aircraft.

The Missile Defense Agency has explored some other 

missile defense concepts and systems—and is likely to 

develop new systems in the future—but none of those 

other systems are deployed now or are likely to be 

deployed soon. MDA also invests heavily in commandand-control systems and sensors to support the missile 

defense mission. However, most of that spending comes 

from DoD’s acquisition funding rather than from the 

O&S budget, so it is not included in this analysis.

14. Intermediate-range ballistic missiles have ranges between 3,000 

and 5,500 kilometers; medium-range ballistic missiles, between 

1,000 and 3,000 kilometers; and short-range ballistic missiles, 

fewer than 1,000 kilometers. Intercontinental ballistic missiles 

have ranges greater than 5,500 kilometers.
CHAPTER 5: DEFENSEWIDE ACTIVITIES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 121

CBO

Purpose and Limitations. Missile defense systems are 

intended to defend against ballistic missiles fired at the 

United States, its allies, or its deployed forces. Ballistic 

missiles, which were developed during World War II, are 

initially powered by a rocket motor that boosts them high 

into the air; after that they coast on an arching (ballistic) 

trajectory, powered only by gravity as they fall to Earth 

toward their target. Ballistic missiles are very difficult to 

intercept once fired—their speed, high-altitude flight, 

and long range mean that developing weapon systems 

capable of destroying them in flight is extremely challenging. Those same characteristics have also made ballistic 

missiles a preferred delivery system for nuclear weapons 

(as discussed in the previous entry). The difficulty of 

defending against nuclear-armed ballistic missiles is one 

of the main reasons that the United States continues to 

rely heavily on deterrence to protect against nuclear 

attacks.

Intercontinental ballistic missiles (ICBMs) and the very 

similar submarine-launched ballistic missiles (SLBMs) 

present the greatest technical challenges to effective missile defense: Their very long range (between continents) 

requires extremely powerful engines, which accelerate 

them to very high speeds and loft them in very high ballistic arcs. Intermediate-range, medium-range, and shortrange ballistic missiles are somewhat less challenging 

because they reach lower maximum speeds and usually fly 

at lower altitudes. In general, ICBMs and SLBMs are the 

most costly and difficult weapon systems to develop and 

are designed to deliver nuclear weapons, meaning that 

usually only the largest nuclear powers possess them. 

Short-range ballistic missiles are much less costly and difficult to develop, are fielded by many countries, and are 

generally armed with conventional explosive payloads 

rather than nuclear warheads. Medium-range ballistic 

missiles are more expensive and less plentiful than their 

short-range counterparts, and intermediate-range ballistic 

missiles are more costly and less common than mediumrange missiles. 

The first missile defense systems were developed by the 

United States and the Soviet Union in the 1960s and 

1970s. They were designed to destroy a ballistic missile 

after its launch by detonating a nuclear warhead in its 

vicinity. However, because of the undesirability of using 

nuclear warheads, the United States began in the 1980s 

to extensively research ways to use conventional explosive 

or kinetic warheads to destroy ballistic missiles.15 The 

initial Patriot missile system, which was fielded as an 

air-defense system in the 1980s, also possessed a limited 

ability to destroy short-range ballistic missiles. Since then, 

the United States has made significant technical progress 

in developing systems to destroy all types of ballistic missiles, and MDA now has systems capable of intercepting 

all of those types of ballistic missiles.

Effective missile defense remains highly challenging. As a 

result, analysts outside DoD have raised a number of concerns about the feasibility of missile defense in general 

and about the performance of current U.S. systems in 

particular—especially against an adversary that can field 

decoy warheads and other countermeasures to confuse 

defense systems. MDA has faced external criticism of its 

test programs and their results, and it is difficult to assess 

how effective the systems that DoD has fielded would be 

in an actual missile attack.

Even if all of its current systems perform as DoD plans, 

the GMD system intended to defend U.S. territory 

against missiles is designed to protect against attacks by 

very small numbers of long-range ballistic missiles—the 

sort of attack that might be launched by a so-called rogue 

state, such as North Korea or Iran. That system is not 

intended to defend the United States against attacks by 

large numbers of nuclear-armed missiles.

Past and Planned Use. During Operation Desert Storm 

in 1991, the Army used Patriot missiles to defend against 

Iraqi Scud missile attacks targeted at Saudi Arabia, Israel, 

and U.S. and coalition forces. The Army’s missiles were 

early-model Patriots rather than the current PAC-3 

design, and their effectiveness in actually shooting down 

Iraqi missiles has been the subject of debate. (Part of the 

difficulty in assessing their performance is that many 

engagements with Scud missiles ended up being near 

misses that may not have destroyed those missiles, resulting in an ambiguous operational record.) PAC-3 missiles 

were employed in 2003 during the invasion of Iraq with 

some success. None of the remaining systems in the current generation of U.S. missile defenses have been used in 

combat.

15. Unlike explosive weapons, kinetic weapons destroy their targets by 

hitting them at high speed. A kinetic warhead can be fairly small 

and thus easier to accelerate to high speed, but it requires much 

more accurate guidance than an explosive or nuclear warhead 

does.
122 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Currently, two of the primary missions for U.S. missile 

defense systems are to protect the United States against a 

limited attack by North Korean nuclear-armed ICBMs 

(using the GMD system) and to protect U.S. forces and 

allies in Europe against an attack by Iranian nucleararmed intermediate-range ballistic missiles (using shipand land-based versions of the Aegis BMD system). Both 

of those missions involve countering a threat that has yet 

to emerge, because neither of those countries is currently 

believed to have effectively combined nuclear warheads 

and ballistic missiles, and neither has yet fielded missiles 

with sufficient range. It is also unclear whether missile 

defenses are required to counter those threats. U.S. 

nuclear forces may be sufficient to deter attacks, as they 

were during the Cold War, although it is possible that 

a reliable missile defense system could enhance the 

effectiveness of the existing U.S. nuclear deterrent. 

(The effect of missile defenses on deterrence is an 

extremely controversial topic.)

The main intended mission for the THAAD and PAC-3 

systems is to defend deployed U.S. forces or U.S. allies 

against attacks by intermediate-, medium-, or short-range 

ballistic missiles. Such a mission is not speculative: Shortrange ballistic missiles have proliferated widely and were 

used against U.S. forces in Operations Desert Storm and 

Iraqi Freedom.
CBO

APPENDIX

A

Size, Costs, and Number of U.S. Forces

This appendix shows, for quick reference, the total 

size and costs of each type of major combat unit in the 

Congressional Budget Office’s analysis (see Table A-1). 

The table also shows how many of each type of unit the 

Department of Defense plans to have in its force each 

year from 2017 to 2021 as reported in DoD’s 2017 

Future Years Defense Program.
124 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table A-1. 

Size, Costs, and Number of U.S. Forces

Continued

Active-Component Armored Brigade

Combat Team 17,450 2,610 9 9 9 9 9

National Guard Armored Brigade 

Combat Team 14,440 820 5 5 5 5 5

Active-Component Stryker Brigade 

Combat Team 17,180 2,560 7 7 7 7 7

National Guard Stryker Brigade 

Combat Team 14,230 800 2 2 2 2 2

Active-Component Infantry Brigade 

Combat Team 16,250 2,410 14 14 14 14 14

National Guard Infantry Brigade 

Combat Team 12,720 700 19 19 19 19 19

Active-Component Aviation Brigade 4,300 890 11 11 10 10 10

Reserve-Component Aviation Brigade 2,750 200 11 12 12 12 12

Army Special-Operations Forces 45,100 a 7,210 b n.a. n.a. n.a. n.a. n.a.

Rest of the Army 12,570 a 3,180 b n.a. n.a. n.a. n.a. n.a.

Aircraft Carrier 6,590 1,180 11 11 11 11 11

Carrier Air Wing 4,860 910 10 10 10 10 10

Arleigh Burke Class Destroyer (DDG-51) 720 140 66 67 69 72 74

Ticonderoga Class Cruiser (CG-47) 550 110 22 22 22 20 20

Littoral Combat Ship 430 100 14 18 22 24 28

Zumwalt Class Destroyer (DDG-1000) 500 100 2 2 3 3 3

Attack Submarinec 390 140 51 52 50 51 51

Amphibious Shipd 1,450 270 35 e 35 e 35 e 35 e 35 e

Active-Component Marine Corps 

Infantry Battalion 5,780 740 24 24 24 24 24

Reserve-Component Marine Corps

Infantry Battalion 4,370 470 8 8 8 8 8

Marine Corps Aircraft Complement 2,750 520 24 24 24 24 24

Ballistic and Guided Missile Submarines 660 170 18 18 18 18 18

Military

Department of the Army

Department of the Navy

(Millions of 2017 dollars)

Number of Units

2017 2018 2019 2020 2021

Annual Cost per Unit

Personnel per Unit
APPENDIX A: COST, SIZE, AND NUMBER OF U.S. FORCES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 125

CBO

Table A-1. Continued

Size, Costs, and Number of U.S. Forces

Continued

P-3 and P-8 Maritime Patrol Aircraft 

Squadronf 1,890 330 8 8 8 8 8

Seabee Construction Engineers 14,200 a 1,860 b n.a. n.a. n.a. n.a. n.a.

Navy Special-Operations Forces 16,440 a 2,370 b n.a. n.a. n.a. n.a. n.a.

Marine Corps Special-Operations Forces 3,530 a 490 b n.a. n.a. n.a. n.a. n.a.

Rest of the Navy 37,990 a 6,550 b n.a. n.a. n.a. n.a. n.a.

Rest of the Marine Corps 770 a 230 b n.a. n.a. n.a. n.a. n.a.

A-10 Attack Aircraft Squadron 1,190 230 16 13 10 6 2

F-15 Fighter Aircraft Squadron 1,540 300 25 25 25 25 26

F-16 Fighter Aircraft Squadron 1,250 220 45 45 46 46 46

F-22 Fighter Aircraft Squadron 2,390 470 13 13 13 13 13

F-35 Fighter Aircraft Squadrong 2,940 570 3 5 7 10 14

B-52 Bomber Aircraft Squadron 3,830 740 4 4 4 4 4

B-1B Bomber Aircraft Squadron 3,980 810 4 4 4 4 4

B-2 Bomber Aircraft Squadron 8,660 1,840 1 1 1 1 1

C-130 Cargo Aircraft Squadron 2,120 360 24 24 23 24 24

C-5 Cargo Aircraft Squadron 2,430 430 3 3 3 3 3

C-17 Cargo Aircraft Squadron 1,390 270 14 15 16 16 16

KC-135 Tanker Aircraft Squadron 1,930 360 30 28 28 27 28

KC-10 Tanker Aircraft Squadron 3,140 580 5 5 4 3 2

KC-46 Tanker Aircraft Squadrong 1,070 180 1 3 4 5 6

MQ-1 "Predator" UAS Squadron 260 70 9 0 0 0 0

RQ-4 "Global Hawk" UAS Squadron 1,840 440 3 3 3 3 3

MQ-9 "Reaper" UAS Squadron 920 160 23 24 26 27 27

Minuteman III Missile Squadronh 2,040 380 9 9 9 9 9

RED HORSE Construction Engineers 19,340 a 2,170 b n.a. n.a. n.a. n.a. n.a.

Air Force Special-Operations Forces 24,070 a 3,730 b n.a. n.a. n.a. n.a. n.a.

Rest of the Air Force 49,010 a 10,000 b n.a. n.a. n.a. n.a. n.a.

Department of the Air Forcef

Military Annual Cost per Unit Number of Units

Personnel per Unit (Millions of 2017 dollars) 2017 2018 2019 2020 2021

Department of the Navy (Continued)
126 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table A-1. Continued

Size, Costs, and Number of U.S. Forces

Source: Congressional Budget Office, using data from the Department of Defense’s 2017 budget request.

n.a. = not applicable; UAS = unmanned air system. 

a. Military personnel for these forces as a whole, rather than personnel per unit.

b. Annual cost for these forces as a whole, rather than cost per unit.

c. Because of data limitations, CBO could not estimate costs for different classes of attack submarines using the framework of this analysis.

d. Because of data limitations, CBO could not estimate costs for different classes of amphibious ships using the framework of this analysis. The costs 

shown here are average costs for ships only (they do not include the costs of the Marine units that would deploy on the ships).

e. Includes two command ships that are considered part of the amphibious fleet in the Department of Defense’s budget documents.

f. Aircraft squadrons are notional squadrons of 12 aircraft (actual squadrons vary in size).

g. Because these aircraft are not yet in full operational service, their actual costs may differ from the planned costs included in the Department of 

Defense’s budget documents, on which these estimates are based.

h. Squadron of 50 Minuteman missiles.

i. Defensewide organizations do not directly fund any military personnel of their own (because all military personnel are part of one of the services). 

Special Operations Command 0 i 5,370 b n.a. n.a. n.a. n.a. n.a.

Defense Health Program for Retirees 0 i 14,720 b n.a. n.a. n.a. n.a. n.a.

Classified Defensewide Funding 0 i 14,540 b

Rest of the Defensewide Organizations 0 i 4,060 b n.a. n.a. n.a. n.a. n.a.

Defensewide Activities

Military Annual Cost per Unit Number of Units

Personnel per Unit 2021 (Millions of 2017 dollars) 2017 2018 2019 2020
CBO

APPENDIX

B

Reconciling CBO’s and DoD’s 

Five-Year Tallies of Funding and Personnel

This appendix shows how the personnel numbers (see 

Table B-1) and costs (see Table B-2) for each type of 

major combat unit, as estimated by the Congressional 

Budget Office, sum to the totals for the Department of 

Defense’s operation and support budget and military 

personnel reported in DoD’s 2017 Future Years Defense 

Program. Supplemental data for Table B-1 and Table B-2 

are available on CBO’s website (www.cbo.gov/publication/

51535).
128 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table B-1. 

Five-Year Tallies of Units’ Military Personnel, 2017 to 2021

Continued

Direct Indirect Overhead

Active-Component Armored Brigade 

Combat Team 45 4,200 9,090 4,160 17,450 189 409 187 785

National Guard Armored Brigade 

Combat Team 25 4,140 9,090 1,210 14,440 104 227 30 361

Active-Component Stryker Brigade 

Combat Team 35 4,440 8,590 4,150 17,180 156 301 145 601

National Guard Stryker Brigade 

Combat Team 10 4,450 8,590 1,190 14,230 45 86 12 142

Active-Component Infantry Brigade 

Combat Team 70 4,230 8,090 3,920 16,250 296 566 275 1,137

National Guard Infantry Brigade 

Combat Team 95 3,560 8,090 1,060 12,720 338 769 101 1,208

Active-Component Aviation Brigade 52 3,020 0 1,280 4,300 157 0 67 224

Reserve-Component Aviation Brigade 59 2,520 0 230 2,750 148 0 14 162

Army Special-Operations Forces n.a. 32,370 a 0 12,730 a 45,100 a 162 0 64 226

Rest of the Army n.a. 8,860 a 0 3,710 a 12,570 a 44 0 19 63

Aircraft Carrier 55 3,200 760 2,620 6,590 176 42 144 362

Carrier Air Wing 50 1,630 1,300 1,930 4,860 81 65 97 243

Arleigh Burke Class Destroyer (DDG-51) 348 340 100 290 720 118 33 100 251

Ticonderoga Class Cruiser (CG-47) 106 250 90 220 550 26 9 23 59

Littoral Combat Ship 106 190 70 170 430 20 8 18 46

Zumwalt Class Destroyer (DDG-1000) 13 220 80 200 500 31 3 7

Attack Submarineb 255 190 50 150 390 48 12 39 99

Amphibious Ship

c 175 d 710 170 580 1,450 123 29 101 254

Active-Component Marine Corps 120 1,490 1,990 2,300 5,780 179 239 276 693

Infantry Battalion

Reserve-Component Marine Corps 40 2,070 560 1,740 4,370 83 22 70 175

Infantry Battalion

Marine Corps Aircraft Complement 120 760 890 1,090 2,750 92 107 131 330

Ballistic and Guided Missile Submarines 90 320 80 260 660 29 7 24 60

Military Personnel per Unit (In thousands)

Five-Year

Total Total

Total of

Units Direct Indirect Overhead

Department of the Army

Total Military Personnel Over the 2017–2021 Period

Department of the Navy
APPENDIX B: RECONCILING CBO’S AND DOD’S FIVE-YEAR TALLIES OF FUNDING AND PERSONNEL THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 129

CBO

Table B-1. Continued

Five-Year Tallies of Units’ Military Personnel, 2017 to 2021

Continued

Direct Indirect Overhead

P-3 and P-8 Maritime Patrol Aircraft 

Squadrone 37 630 500 750 1,890 24 19 28 71

Seabee Construction Engineers n.a. 8,550 a 0 5,650 a 14,200 a 43 0 28 71

Navy Special-Operations Forces n.a. 9,900 a 0 6,550 a 16,440 a 49 0 33 82

Marine Corps Special-Operations Forces n.a. 2,130 a 0 1,410 a 3,530 a 11 0 7 18

Rest of the Navy n.a. 22,860 a 0 15,120 a 37,990 a 114 0 76 190

Rest of the Marine Corps n.a. 460 a 0 310 a 770 a 20 2 4

A-10 Attack Aircraft Squadron 46 350 440 400 1,190 16 20 19 55

F-15 Fighter Aircraft Squadron 124 430 590 520 1,540 53 73 65 191

F-16 Fighter Aircraft Squadron 226 450 370 420 1,250 102 85 96 282

F-22 Fighter Aircraft Squadron 65 430 1,150 810 2,390 28 75 53 156

F-35 Fighter Aircraft Squadronf 37 430 1,510 1,000 2,940 16 57 37 110

B-52 Bomber Aircraft Squadron 19 1,310 1,220 1,300 3,830 25 23 24 72

B-1B Bomber Aircraft Squadron 21 940 1,680 1,350 3,980 20 36 29 85

B-2 Bomber Aircraft Squadron 7 2,120 3,600 2,940 8,660 14 24 20 58

C-130 Cargo Aircraft Squadron 118 800 590 720 2,120 95 70 85 251

C-5 Cargo Aircraft Squadron 16 780 820 830 2,430 13 13 13 40

C-17 Cargo Aircraft Squadron 76 450 460 470 1,390 35 35 36 106

KC-135 Tanker Aircraft Squadron 141 610 660 650 1,930 87 93 92 272

KC-10 Tanker Aircraft Squadron 18 900 1,170 1,060 3,140 17 22 20 58

KC-46 Tanker Aircraft Squadronf 20 640 70 360 1,070 13 1 7 21

MQ-1 "Predator" UAS Squadron 9 90 80 90 260 11 1 2

RQ-4 "Global Hawk" UAS Squadron 15 470 750 630 1,840 7 11 9 28

MQ-9 "Reaper" UAS Squadron 128 340 270 310 920 44 34 40 118

Minuteman III Missile Squadrong 45 690 650 690 2,040 31 29 31 92

RED HORSE Construction Engineers n.a. 12,780 a 0 6,560 a 19,340 a 64 0 33 97

Air Force Special-Operations Forces n.a. 15,900 a 0 8,170 a 24,070 a 80 0 41 120

Rest of the Air Force n.a. 32,370 a 0 16,630 a 49,010 a 162 0 83 245

(In thousands)

Direct Indirect Overhead Total Total

Department of the Air Forcee

Units

Department of the Navy (Continued)

Total of Military Personnel per Unit

Five-Year Total Military Personnel Over the 2017–2021 Period
130 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table B-1. Continued

Five-Year Tallies of Units’ Military Personnel, 2017 to 2021

Source: Congressional Budget Office, using data from the Department of Defense’s 2017 budget request.

“Direct” personnel are associated with a major combat unit, “indirect” personnel are associated with units that support the major combat unit, and 

“overhead” personnel are associated with the major combat unit’s share of administrative or overhead activities. For more information, see Chapter 1. 

Supplemental data for this table are available on CBO’s website (www.cbo.gov/publication/51535).

n.a. = not applicable; UAS = unmanned air system. 

a. Military personnel for these forces as a whole, rather than personnel per unit.

b. Because of data limitations, CBO could not estimate personnel numbers for different classes of attack submarines using the framework of this 

analysis.

c. Because of data limitations, CBO could not estimate personnel numbers for different classes of amphibious ships using the framework of this analysis. 

The numbers shown here are average personnel of ships only (they do not include the personnel of the Marine units that would deploy on the ships).

d. Includes two command ships that are considered part of the amphibious fleet in the Department of Defense’s budget documents.

e. Aircraft squadrons are notional squadrons of 12 aircraft (actual squadrons vary in size).

f. Because these aircraft are not yet in full operational service, their actual personnel numbers may differ from the planned personnel numbers included 

in the Department of Defense’s budget documents, on which these estimates are based.

g. Squadron of 50 Minuteman missiles.

h. Defensewide organizations do not directly fund any military personnel of their own (because all military personnel are part of one of the services). 

In addition, in the analytic framework used for this report, defensewide organizations are considered to not have any units supporting them and thus 

to not have any indirect personnel or costs. No overhead costs are shown for defensewide organizations because such costs are apportioned on the 

basis of the number of military personnel in an activity.

Direct Indirect Overhead

Special Operations Command n.a. 0 0 0 0 00 0 0

Defense Health Program for Retirees n.a. 0 0 0 0 00 0 0

Classified Defensewide Funding n.a. 0 0 0 0 00 0 0

Rest of the Defensewide Organizations n.a. 0 0 0 0 00 0 0

Five-Year Total 3,780 3,653 2,946 10,379

National Defense Budget 

Estimates for Fiscal Year 2017 10,379

Total Military Personnel Over the 2017–2021 Period

Defensewide Activitiesh

Five-Year

Total of Military Personnel per Unit (In thousands)

Units Direct Indirect Overhead Total Total
APPENDIX B: RECONCILING CBO’S AND DOD’S FIVE-YEAR TALLIES OF FUNDING AND PERSONNEL THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 131

CBO

Table B-2. 

Five-Year Tallies of Units’ Costs, 2017 to 2021

Continued

Active-Component Armored Brigade 

Combat Team 45 500 840 1,280 2,610 22.3 37.7 57.5 117.5

National Guard Armored Brigade 

Combat Team 25 180 390 240 820 4.6 9.8 6.1 20.5

Active-Component Stryker Brigade 

Combat Team 35 500 790 1,280 2,560 17.4 27.7 44.6 89.7

National Guard Stryker Brigade 

Combat Team 10 190 370 240 800 1.9 3.7 2.4 8.0

Active-Component Infantry Brigade 

Combat Team 70 450 750 1,210 2,410 31.8 52.2 84.6 168.5

National Guard Infantry Brigade 

Combat Team 95 140 350 220 700 13.2 33.1 20.5 66.7

Active-Component Aviation Brigade 52 490 0 410 890 25.3 0 21.2 46.5

Reserve-Component Aviation Brigade 59 160 0 50 200 9.3 0 2.7 12.0

Army Special-Operations Forces n.a. 3,190 a 0 4,020 a 7,210 a 15.9 0 20.1 36.1

Rest of the Army n.a. 2,000 a 0 1,180 a 3,180 a 10.0 0 5.9 15.9

Aircraft Carrier 55 470 180 530 1,180 25.6 10.2 29.2 65.0

Carrier Air Wing 50 330 200 390 910 16.3 9.8 19.6 45.7

Arleigh Burke Class Destroyer (DDG-51) 348 60 20 60 140 19.8 8.2 20.2 48.3

Ticonderoga Class Cruiser (CG-47) 106 40 20 40 110 4.7 2.1 4.7 11.5

Littoral Combat Ship 106 40 20 30 100 4.7 2.1 3.7 10.5

Zumwalt Class Destroyer (DDG-1000) 13 40 20 40 100 0.5 0.2 0.5 1.3

Attack Submarineb 255 70 40 30 140 17.8 10.4 8.0 36.2

Amphibious Ship

c 175 d 110 40 120 270 19.6 7.8 20.5 47.9

Active-Component Marine Corps 

Infantry Battalion 120 140 140 470 740 16.4 16.9 55.9 89.3

Reserve-Component Marine Corps 

Infantry Battalion 40 70 50 350 470 2.9 1.8 14.1 18.8

Marine Corps Aircraft Complement 120 160 140 220 520 19.7 16.5 26.6 62.9

Ballistic and Guided Missile Submarines 90 70 40 50 170 6.4 3.7 4.8 14.9

Department of the Navy

Overhead Total

(Billions of 2017 dollars)

Indirect

(Millions of 2017 dollars)

Total Cost Over the 2017–2021 Period

Department of the Army

Total of

Units Direct Indirect Overhead Total Direct

Five-Year Annual Cost per Unit
132 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

CBO

Table B-2. Continued

Five-Year Tallies of Units’ Costs, 2017 to 2021

Continued

Department of the Navy (Continued)

P-3 and P-8 Maritime Patrol Aircraft 

Squadrone 37 110 70 150 330 4.2 2.5 5.7 12.4

Seabee Construction Engineers n.a. 720 a 0 1,150 a 1,860 a 3.6 0 5.7 9.3

Navy Special-Operations Forces n.a. 1,050 a 0 1,330 a 2,370 a 5.2 0 6.6 11.9

Marine Corps Special-Operations Forces n.a. 210 a 0 280 a 490 a 1.0 0 1.4 2.5

Rest of the Navy n.a. 3,490 a 0 3,060 a 6,550 a 17.4 0 15.3 32.8

Rest of the Marine Corps n.a. 160 a 0 60 a 230 a 0.8 0 0.3 1.1

A-10 Attack Aircraft Squadron 46 80 60 90 230 3.5 2.7 4.3 10.5

F-15 Fighter Aircraft Squadron 124 100 80 120 300 12.6 10.0 15.0 37.6

F-16 Fighter Aircraft Squadron 226 70 50 100 220 15.4 11.5 22.1 49.1

F-22 Fighter Aircraft Squadron 65 120 160 190 470 8.0 10.3 12.2 30.5

F-35 Fighter Aircraft Squadronf 37 130 210 230 570 4.9 7.7 8.6 21.2

B-52 Bomber Aircraft Squadron 19 270 170 300 740 5.0 3.1 5.6 13.8

B-1B Bomber Aircraft Squadron 21 270 230 310 810 5.7 4.9 6.6 17.2

B-2 Bomber Aircraft Squadron 7 670 490 680 1,840 4.5 3.3 4.5 12.3

C-130 Cargo Aircraft Squadron 118 110 80 170 360 12.9 9.6 19.7 42.1

C-5 Cargo Aircraft Squadron 16 130 110 190 430 2.1 1.8 3.1 7.0

C-17 Cargo Aircraft Squadron 76 90 60 110 270 7.1 4.8 8.3 20.2

KC-135 Tanker Aircraft Squadron 141 110 90 150 360 16.1 12.7 21.3 50.1

KC-10 Tanker Aircraft Squadron 18 180 160 250 580 3.3 2.9 4.5 10.7

KC-46 Tanker Aircraft Squadronf 20 80 10 80 180 1.6 0.2 1.7 3.5

MQ-1 "Predator" UAS Squadron 9 40 10 20 70 0.3 0.1 0.2 0.6

RQ-4 "Global Hawk" UAS Squadron 15 190 100 140 440 2.9 1.5 2.2 6.6

MQ-9 "Reaper" UAS Squadron 128 50 40 70 160 7.0 4.7 9.3 20.9

Minuteman III Missile Squadrong 45 130 90 160 380 5.9 4.0 7.2 17.1

RED HORSE Construction Engineers n.a. 660 a 0 1,520 a 2,170 a 3.3 0 7.6 10.9

Air Force Special-Operations Forces n.a. 1,840 a 0 1,890 a 3,730 a 9.2 0 9.4 18.7

Rest of the Air Force n.a. 6,160 a 0 3,840 a 10,000 a 30.8 0 19.2 50.0

Five-Year

Total of (Millions of 2017 dollars)

Department of the Air Forcee

Annual Cost per Unit

Units Direct Indirect Overhead Total

(Billions of 2017 dollars)

Direct Indirect Overhead Total

Total Cost Over the 2017–2021 Period
APPENDIX B: RECONCILING CBO’S AND DOD’S FIVE-YEAR TALLIES OF FUNDING AND PERSONNEL THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 133

CBO

Table B-2. Continued

Five-Year Tallies of Units’ Costs, 2017 to 2021

Source: Congressional Budget Office, using data from the Department of Defense’s 2017 budget request.

“Direct” costs are associated with a major combat unit, “indirect” costs are associated with units that support the major combat unit, and “overhead” 

costs are associated with the major combat unit’s share of administrative or overhead activities. For more information, see Chapter 1. 

Supplemental data for this table are available on CBO’s website (www.cbo.gov/publication/51535).

n.a. = not applicable; UAS = unmanned air system. 

a. Annual cost for these forces as a whole, rather than cost per unit.

b. Because of data limitations, CBO could not estimate costs for different classes of attack submarines using the framework of this analysis.

c. Because of data limitations, CBO could not estimate costs for different classes of amphibious ships using the framework of this analysis. The costs 

shown here are average costs for ships only (they do not include the costs of the Marine units that would deploy on the ships).

d. Includes two command ships that are considered part of the amphibious fleet in the Department of Defense’s budget documents.

e. Aircraft squadrons are notional squadrons of 12 aircraft (actual squadrons vary in size).

f. Because these aircraft are not yet in full operational service, their actual costs may differ from the planned costs included in the Department of 

Defense’s budget documents, on which these estimates are based.

g. Squadron of 50 Minuteman missiles.

Special Operations Command n.a. 5,370 a 0 0 5,370 a 26.9 0 0 26.9

Defense Health Program for Retirees n.a. 14,720 a 0 0 14,720 a 73.6 0 0 73.6

Classified Defense Funding n.a. 14,540 a 0 0 14,540 a 72.7 0 0 72.7

Rest of the Defensewide Organizations n.a. 4,060 a 0 0 4,060 a 20.3 0 0 20.3

Five-Year Total 694.2 352.6 701.3 1,748.1

1,748.1

Five-Year

(Millions of 2017 dollars) (Billions of 2017 dollars)

Estimates for Fiscal Year 2017

Annual Cost per Unit Total Cost Over the 2017–2021 Period

National Defense Budget 

Defensewide Activities

Units Direct Indirect Overhead Total Direct Indirect Overhead Total

Total of

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APPENDIX

C

Military Operations and Planning Scenarios 

Referred to in This Report

In describing the past and planned use of various types 

of forces, this primer mentions a number of military 

operations that the United States has engaged in since 

World War II, as well as a number of scenarios that the 

Department of Defense (DoD) has used to plan for 

future conflicts. Those operations and planning scenarios 

are summarized below.

Military Operations

1950–1953: Korean War. U.S. forces defended South 

Korea (the Republic of Korea) from an invasion by North 

Korea (the Democratic People’s Republic of Korea). 

North Korean forces initially came close to overrunning 

the entire Korean Peninsula before being pushed back. 

Later, military units from China (the People’s Republic 

of China) intervened when U.S. forces approached the 

Chinese border. That intervention caused the conflict to 

devolve into a stalemate at the location of the current 

border between North and South Korea.

September 1950: Inchon Landing. U.S. marines led an 

amphibious assault on the South Korean port of Inchon. 

At the time, Inchon was well behind the North Korean 

military’s lines, and the insertion of U.S. forces there contributed to the collapse and retreat of the North Korean 

invasion force.

1964–1975: Vietnam War. U.S. forces attempted to 

defend the government of South Vietnam (the Republic 

of Vietnam) from communist insurgents backed by 

North Vietnam (the People’s Republic of Vietnam) and 

from military incursions by North Vietnam’s ground 

forces. Ultimately, the United States withdrew ground 

forces from South Vietnam in 1973 and air support from 

the country in 1975. Subsequently, all of South Vietnam 

was conquered by North Vietnamese ground forces, uniting the two countries under a single government.

1965–1972, intermittently: Bombing of North 

Vietnam. Several U.S. bombing campaigns were conducted on the territory of North Vietnam during the war 

(as opposed to air operations in South Vietnam, which 

were essentially continuous in support of U.S. and South 

Vietnamese ground forces). The most notable campaigns 

included Operations Rolling Thunder, Linebacker, and 

Linebacker II.

1972: Easter Offensive. This offensive, launched by 

North Vietnamese ground forces, was largely defeated by 

South Vietnamese ground forces along with heavy air 

support from U.S. forces.

1975: Spring Offensive. This was the final offensive 

launched by North Vietnamese ground forces during the 

war. Unlike in the Easter Offensive, the United States did 

not provide air support to South Vietnamese ground 

forces, and North Vietnamese forces fully conquered 

South Vietnam.

1980: Operation Eagle Claw. U.S. special-operations 

forces attempted to rescue hostages held in Tehran in the 

wake of the Iranian revolution. The operation failed to 

meet any of its objectives.

1982: Falklands War. The United Kingdom recaptured 

the Falkland Islands from Argentina, which had occupied 

them. The campaign involved a U.K. naval task force 

that secured the seas around the Falklands prior to an 

amphibious assault by commandos and royal marines 

that retook the islands. The war included some of the few 

examples of modern naval combat since World War II: 

A U.K. nuclear submarine sank an Argentinian ship (the 

ARA General Belgrano), and Argentinian aircraft sank several U.K. ships (most notably, the HMS Sheffield) with 

bombs and cruise missiles.
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1986: Operation El Dorado Canyon. Air Force and 

Navy aircraft bombed targets in Libya in response to 

terrorist attacks sponsored by the Libyan government.

1987: USS Stark Incident. During the Iran–Iraq War, 

an Iraqi fighter aircraft fired two cruise missiles at the 

USS Stark, a U.S frigate on patrol in the Persian Gulf. 

Both missiles hit the Stark, causing casualties and 

damaging the ship.

1990–1991: Operation Desert Shield. U.S. forces 

were deployed to Saudi Arabia to protect that country 

from a potential invasion by Iraq in the aftermath of 

Iraq’s August 1990 invasion of Kuwait. The first U.S. 

ground troops deployed were the 82nd Airborne Division, but the deployment ultimately involved a large 

enough force to invade Iraq and liberate Kuwait (see 

Operation Desert Storm, below). The U.S. military also 

enforced a naval blockade of Iraq. During that blockade, 

two U.S. warships, the USS Princeton and USS Tripoli,

were damaged by Iraqi sea mines.

1991: Operation Desert Storm. During Operation Desert Shield, the United States’ goals shifted from defending 

Saudi Arabia from an Iraqi attack to removing Iraqi forces 

from Kuwait. Operation Desert Storm was the operation 

to liberate Kuwait and destroy Iraqi ground forces. After 

an air campaign lasting 42 days, the United States 

launched a ground campaign that achieved its primary 

goals within 4 days. This conflict saw the first use of 

the Patriot missile system to defend against Iraqi Scud 

missiles fired at Saudi Arabia and Israel.

1991–2003: Operations Northern Watch and 

Southern Watch. This pair of operations was the U.S. 

effort to maintain northern and southern no-fly zones 

over Iraq (intended to protect Iraqi Kurds and Shiites, 

respectively) between Operation Desert Storm and 

Operation Iraqi Freedom.

1992–1993: Operation Restore Hope. This operation 

was the U.S. military component of the United Nations’ 

effort to restore order in Somalia to allow for the distribution of humanitarian aid. During the October 1993 

battle of Mogadishu, a U.S. special-operations force was 

pinned down and isolated in Somalia’s capital by hostile 

militias and suffered several casualties—an incident featured in the book and film Black Hawk Down. That incident eventually led the United States to abandon the 

operation.

1994–1995: Operation Uphold Democracy. Initially 

planned as a U.S. invasion of Haiti to overthrow the 

Haitian government, this operation became a peacekeeping mission after a diplomatic settlement was 

reached in which the leaders of the Haitian government 

agreed to step down.

1998: Operation Infinite Reach. Navy ships launched a 

series of strikes with Tomahawk cruise missiles at targets 

in Sudan and Afghanistan in response to the bombings of 

the U.S. embassies in Kenya and Tanzania earlier that 

year.

1999: Operation Noble Anvil. This was the U.S. contribution to the North Atlantic Treaty Organization’s 

(NATO’s) operations against Serbia, intended to force 

Serbia’s leadership to relinquish control of the province 

of Kosovo. The majority of the operation consisted of a 

three-month bombing campaign against targets in Serbia 

and against Serbian military units in Kosovo. A diplomatic settlement was ultimately reached in which the 

Serbian leadership agreed to NATO’s demands.

1999: Task Force Hawk. A component of the U.S. 

campaign against Serbia, this Army task force was originally intended to deploy a battalion of AH-64 attack helicopters to Tirana, Albania. For a variety of reasons, the 

task force grew in size, was slow to deploy, and never 

participated in the campaign.

2000: USS Cole Bombing. In this incident, a small boat 

loaded with explosives was used to launch a suicide attack 

against the destroyer USS Cole while it was docked in the 

port of Aden, Yemen. The resulting explosion blew a 

large hole in the hull of the Cole, killed 17 sailors, and 

wounded several others.

2001: Operation Enduring Freedom. Although this 

name technically applied to a wide variety of operations 

(also referred to as the Global War on Terror), the main 

component of this operation was the invasion of 

Afghanistan to oust the Taliban government and apprehend Osama bin Laden after the September 11, 2001, 

terrorist attacks in the United States. Major portions of 

the offensive involved U.S. special forces supporting 

Afghan ground forces of the Northern Alliance and an air 

assault by U.S. Marines on the city of Kandahar.

December 2001: Battle of Tora Bora. U.S. special 

forces attempted to capture Osama bin Laden and other 
APPENDIX C: MILITARY OPERATIONS AND PLANNING SCENARIOS REFERRED TO IN THIS REPORT THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 137

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elements of the Al Qaeda leadership in a mountainous 

region of Afghanistan. Despite U.S. confidence that bin 

Laden was present in the region, he was not found, 

although it is unclear whether that outcome occurred 

because he was not present or because of operational 

missteps.

2001–Present: Occupation/International Security 

Assistance Force. Since Operation Enduring Freedom, 

the United States has continuously maintained military 

forces in Afghanistan (often as part of a NATO security 

assistance force) in an effort to support the Afghan government against insurgents, warlords, a resurgent Taliban, 

and other destabilizing elements (since 2015, under the 

name Operation Freedom’s Sentinel). For much of that 

time, U.S. forces in Afghanistan consisted of between one 

and three brigades of ground troops, but those forces 

were temporarily increased in 2009 as part of a surge.

2003: Operation Iraqi Freedom. U.S. forces invaded 

Iraq with the goal of destroying the government of 

Saddam Hussein. Army and Marine forces advancing 

from Kuwait formed the bulk of the U.S. offensive 

power, but U.S. Army and Kurdish forces in the north 

of Iraq and an extensive U.S. air campaign were also key 

parts of the operation. After three weeks, U.S. forces 

captured Baghdad, and Saddam Hussein’s government 

disintegrated, although some pockets of resistance 

remained.

2003–2011: Occupation of Iraq. The United States 

maintained military forces in Iraq for eight years after 

Operation Iraqi Freedom in an effort to support the Iraqi 

government against insurgents, loyalists of the former 

regime, local militias, and other destabilizing elements, 

especially during the Iraqi civil war of 2006 and 2007. 

For much of that time, U.S. forces in Iraq consisted of 

between 15 and 18 brigades of ground forces, but those 

forces were temporarily increased in 2007 as part of a 

surge.

2011: Operation Neptune Spear. U.S. special forces 

raided a compound in Abbottabad, Pakistan, with the 

intent to capture or kill Osama bin Laden. The raid was 

a success, and bin Laden was killed in the action.

2011: Operation Odyssey Dawn. This was the U.S. 

contribution to NATO’s operations against Libya, 

intended to enforce a no-fly zone against the government 

of Muammar Gaddafi. The operation included cruise 

missile strikes and a naval blockade, but the majority of 

the campaign involved using tactical aviation to attack 

and destroy Libyan government military units. Libyan 

rebel groups captured and killed Gaddafi during the 

operation, ending his regime.

2014–Present: Operation Inherent Resolve. The 

United States is currently conducting air strikes against 

the Islamic State group (known variously as ISIS, ISIL, 

and Daesh) in Iraq and Syria. The United States has also 

committed a limited number of special forces to assist 

Kurdish groups fighting the Islamic State.

DoD Planning Scenarios

The Department of Defense uses scenarios for planning 

purposes to prepare for the types of conflicts that it considers especially relevant or challenging. Such scenarios 

are not war plans; they are descriptions of hypothetical 

conflicts that can be used in various types of analytic exercises rather than detailed plans that could be used in the 

event of an actual conflict. DoD’s scenarios are not necessarily considered likely possibilities—some are useful as 

examples of worst-case planning, whereas others incorporate features that are considered important for understanding future developments in warfighting. Some of 

the scenarios that DoD uses involve the following areas:

North Korea. Scenarios for North Korea typically postulate an attack by that country’s ground forces on South 

Korean territory that requires U.S. assistance to repel. 

North Korea is assumed to use ballistic missiles to try to 

complicate the U.S. response in various ways, such as by 

attacking ports and airfields in South Korea with chemical weapons to hinder the arrival of U.S. reinforcements 

or attacking the United States’ allies in the region (such as 

Japan) to reduce diplomatic support for U.S. goals. 

Those scenarios allow DoD to consider a variety of issues, 

including how to provide missile defense to allies, how 

quickly U.S. forces can be deployed, and how to respond 

to the use of chemical weapons.

Strait of Hormuz. Scenarios for the Strait of Hormuz 

(the narrow waterway that connects the Persian Gulf to 

the Arabian Sea) typically postulate a conflict in which 

Iran attempts to use submarines, cruise missiles, and 

small boats to close the Persian Gulf to U.S. Navy warships and civilian shipping at the Strait of Hormuz. 

Those scenarios allow DoD to consider such factors as 

the difficulty of projecting naval power in coastal regions 
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(where defenders have many advantages), ways to counter 

nontraditional threats such as small boats, and other 

antiaccess challenges.

Taiwan. Scenarios for Taiwan typically postulate an 

attempt by China (the People’s Republic of China) to 

force Taiwan (the Republic of China) to reunite with it or 

to prevent Taiwan from making a formal declaration of 

independence. China is assumed to use air strikes, cruise 

missiles, ballistic missiles, and possibly an amphibious 

attack against Taiwan, while attempting to use its air and 

naval forces to prevent the United States from defending 

Taiwan. Such scenarios allow DoD to plan for dealing 

with a powerful adversary that has a variety of advanced 

weapons, especially in a naval context. The naval angle is 

important because combat between modern warships has 

occurred only once since World War II (during the 1982 

Falklands War), and the scarcity of such examples means 

that there is a great deal of uncertainty about what combat between warships might look like now.

South China Sea. Scenarios for the South China Sea typically postulate that the United States would respond to a 

request for military assistance from one or more of the 

countries that dispute the claims of sovereignty that 

China (the People’s Republic of China) has made over 

several islands and their territorial waters in the South 

China Sea. In those scenarios, China is assumed to have 

used military force to resolve territorial disputes in its 

favor, and U.S. air and naval forces would be required to 

do one or more of the following: defend the opposing 

countries against Chinese attacks, remove the Chinese 

military presence from disputed islands, or restore freedom of navigation in the South China Sea. For the purpose of force planning, such scenarios resemble Taiwan 

scenarios, requiring similar forces against the same opponent in almost the same theater of operations. But they 

suggest different forms of peacetime preparation, including establishing cooperative agreements with the governments of countries that border the South China Sea, such 

as the Philippines or Vietnam.

Two Major Regional Conflicts or Major Theater Wars. 

In the 1990s, U.S. planners used a pair of scenarios 

(called major regional conflicts or, later, major theater 

wars) occurring at the same, or nearly the same, time as 

the formal benchmark for most planning decisions about 

the military’s force structure. One scenario was the North 

Korea scenario described above. The other scenario was 

an Iraqi invasion of Kuwait and Saudi Arabia (essentially, 

a hypothetical variant of Operations Desert Storm and 

Desert Shield in which Iraq’s offensive did not stop at 

the Saudi Arabia–Kuwait border). That pair of scenarios 

was DoD’s planning framework, with some variations, 

for about a decade. It dominated the department’s planning during the period between the collapse of the Soviet 

Union and the terrorist attacks of September 11, 2001.
LIST OF TABLES AND FIGURES THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER 139

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List of Tables and Figures

Tables

S-1. Number, Size, and Costs of Selected U.S. Forces 2

2-1 Number of Major Combat Units in the Army, 2017 and 2021 18

2-2 Average Distribution of the Department of the 

Army’s Military Personnel, 2017 to 2021 20

3-1 Number of Major Combat Units in the Navy and Marine Corps, 2017 and 2021 46

3-2 Average Distribution of the Department of the 

Navy’s Military Personnel, 2017 to 2021 47

4-1 Number of Major Combat Units in the Air Force, 2017 and 2021 82

4-2 Average Distribution of the Department of the 

Air Force’s Military Personnel, 2017 to 2021 83

A-1. Size, Costs, and Number of U.S. Forces 124

B-1. Five-Year Tallies of Units’ Military Personnel, 2017 to 2021 128

B-2. Five-Year Tallies of Units’ Costs, 2017 to 2021 131

Figures

S-1. Five-Year Average of Operation and Support Funding for 

Department of the Army Units 3

S-2. Five-Year Average of Operation and Support Funding for 

Department of the Navy Units 4

S-3. Five-Year Average of Operation and Support Funding for 

Department of the Air Force Units 4

2-1. Units, Equipment, and Personnel in an Army Armored Brigade Combat Team 24

2-2. Legend for Army Equipment and Personnel 26

2-3. Units, Equipment, and Personnel in an Army Stryker Brigade Combat Team 30

2-4. Units, Equipment, and Personnel in an Army Infantry Brigade Combat Team 34

3-1. Ships, Aircraft, and Personnel in a Navy Carrier Strike Group 54

3-2. Ships, Aircraft, Equipment, and Personnel in a Navy Amphibious Ready Group and a 

Marine Expeditionary Unit 62

4-1. Aircraft and Personnel in Notional Air Force Tactical Aviation Squadrons 87

4-2. Aircraft and Personnel in Notional Air Force Bomber Squadrons 90

4-3. Aircraft and Personnel in Notional Air Force Airlift Squadrons 94

4-4. Aircraft and Personnel in Notional Air Force Air Refueling Squadrons 98

4-5. Aircraft and Personnel in Notional Air Force Unmanned Air System Squadrons 101
140 THE U.S. MILITARY’S FORCE STRUCTURE: A PRIMER JULY 2016

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About This Document

This Congressional Budget Office report was prepared at the request of the former Ranking Member 

of the Senate Committee on the Budget. In keeping with CBO’s mandate to provide objective, 

impartial analysis, it makes no recommendations. 

Adam Talaber of CBO’s National Security Division prepared the report with guidance from 

David Mosher and Matthew Goldberg. David Arthur, Elizabeth Bass, Michael Bennett, Daniel Frisk 

(formerly of CBO), Bernard Kempinski, Eric Labs, and Carla Tighe Murray provided comments or 

fact-checked the report. Bernard Kempinski also created the unit graphics for Chapters 2, 3, and 4.

Sarah Jennings, Kent Christensen, Bill Ma, David Newman, Dawn Regan, and Matt Schmit of CBO 

reviewed earlier drafts of the report and provided comments, as did Douglas Elmendorf, formerly of 

CBO; Irv Blickstein and John Gordon of the RAND Corporation; Frank Lewis of the Department of 

Energy’s National Nuclear Security Administration; and David McNichol of the Institute for Defense 

Analyses. (The assistance of external reviewers implies no responsibility for the final product, which 

rests solely with CBO.) 

Jeffrey Kling and Robert Sunshine reviewed the report, and Christian Howlett edited it, with assistance 

from Kate Kelly. Maureen Costantino designed the cover and prepared the report for publication, 

with assistance from Jeanine Rees. An electronic version of the report is available on CBO’s website 

(www.cbo.gov/publication/51535).

Keith Hall 

Director

July 2016