United States Department of Defense

The **United States Department of Defense** (**DoD**, **USDOD**, or **DOD**) is an executive branch department of the federal government of the United States charged with coordinating and supervising all agencies and functions of the U.S. government directly related to national security and the United States Armed Forces. As of June 2022, the U.S. Department of Defense is the largest employer in the world, with over 1.34 million active-duty service members, including soldiers, marines, sailors, airmen, and guardians. DoD also maintains over 778,000 National Guard and reservists, and over 747,000 civilians bringing the total to over 2.87 million employees. Headquartered at the Pentagon in Arlington County, Virginia, just outside Washington, D.C., DoD's stated mission is to provide "the military forces needed to deter war and ensure our nation's security".

The Department of Defense is headed by the secretary of defense, a cabinet-level head who reports directly to the president of the United States. Beneath the Department of Defense are three subordinate military departments: the Department of the Army, the Department of the Navy, and the Department of the Air Force. In addition, four national intelligence services are subordinate to the Department of Defense: the Defense Intelligence Agency (DIA), the National Security Agency (NSA), the National Geospatial-Intelligence Agency (NGA), and the National Reconnaissance Office (NRO). Other Defense agencies include the Defense Advanced Research Projects Agency (DARPA), the Defense Logistics Agency (DLA), the Missile Defense Agency (MDA), the Defense Health Agency (DHA), Defense Threat Reduction Agency (DTRA), the Defense Counterintelligence and Security Agency (DCSA), the Space Development Agency (SDA) and the Pentagon Force Protection Agency (PFPA), all of which are subordinate to the secretary of defense. Additionally, the Defense Contract Management Agency (DCMA) is responsible for administering contracts for the DoD. Military operations are managed by eleven regional or functional unified combatant commands. The Department of Defense also operates several joint services schools, including the Eisenhower School (ES) and the National War College (NWC).

## Organizational Structure

The The secretary of defense, appointed by the president with the advice and consent of the Senate, is by federal law (10 U.S.C. § 113) the head of the Department of Defense, "the principal assistant to the President in all matters relating to Department of Defense", and has "authority, direction, and control over the Department of Defense". Because the Constitutionvests all military authority in Congress and the president, the statutory authority of the secretary of defense is derived from their constitutional authority. Since it is impractical for either Congress or the president to participate in every piece of Department of Defense affairs, the secretary of defense and the secretary's subordinate officials generally exercise military authority.

The Department of Defense is composed of the Office of the Secretary of Defense (OSD), the Joint Chiefs of Staff (JCS) and the Joint Staff (JS), Office of the Inspector General (DODIG), the Combatant Commands, the Military Departments (Department of the Army (DA), Department of the Navy (DON) & Department of the Air Force (DAF)), the Defense Agencies and Department of Defense Field Activities, the National Guard Bureau (NGB), and such other offices, agencies, activities, organizations, and commands established or designated by law, or by the president or by the secretary of defense.

Department of Defense Directive 5100.01 describes the organizational relationships within the department, and is the foundational issuance for delineating the major functions of the department. The latest version, signed by former secretary of defense Robert Gates in December 2010, is the first major re-write since 1987.

### Office of the Secretary of Defense

The Office of the Secretary of Defense (OSD) is the secretary and their deputies, including predominantly civilian staff.

OSD is the principal staff element of the Secretary of Defense in the exercise of policy development, planning, resource management, fiscal and program evaluation and oversight, and interface and exchange with other U.S. federal government departments and agencies, foreign governments, and international organizations, through formal and informal processes. OSD also performs oversight and management of the Defense Agencies, Department of Defense Field Activities, and specialized Cross Functional Teams.

#### Defense agencies

OSD also supervises the following Defense Agencies:

* Armed Forces Radiobiology Research Institute (AFRRI)
* Department of Defense Education Activity (DoDEA)
* Defense Advanced Research Projects Agency (DARPA)
* Defense Commissary Agency (DeCA)
* Defense Contract Audit Agency (DCAA)
* Defense Contract Management Agency (DCMA)
* Defense Finance and Accounting Service (DFAS)
* Defense Information Systems Agency (DISA)
* Defense Legal Services Agency
* Defense Logistics Agency (DLA)
* Defense POW/MIA Accounting Agency (DPAA)
* Defense Security Cooperation Agency (DSCA)
* Defense Counterintelligence and Security Agency (DCSA)
* Defense Technical Information Center (DTIC)
* Defense Threat Reduction Agency (DTRA)
* Space Development Agency (SDA)

#### National intelligence agencies

Several defense agencies are members of the United States Intelligence Community. These are national-level intelligence services that operate under the Department of Defense jurisdiction but simultaneously fall under the authorities of the Office of the Director of National Intelligence. They fulfill the requirements of national policymakers and war planners, serve as Combat Support Agencies, and also assist non-Department of Defense intelligence or law enforcement services such as the Central Intelligence Agency and the Federal Bureau of Investigation.

The military services each have their own intelligence elements that are distinct from but subject to coordination by national intelligence agencies under the Department of Defense. Department of Defense manages the nation's coordinating authorities and assets in disciplines of signals intelligence, geospatial intelligence, and measurement and signature intelligence, and also builds, launches, and operates the Intelligence Community's satellite assets. Department of Defense also has its own human intelligence service, which contributes to the CIA's human intelligence efforts while also focusing on military human intelligence priorities. These agencies are directly overseen by the Under Secretary of Defense for Intelligence and Security.

## Joint Chiefs of Staff

The Joint Chiefs of Staff (JCS) is a body of senior uniformed leaders in the Department of Defense who advise the secretary of defense, the Homeland Security Council, the National Security Council and the president on military matters. The composition of the Joint Chiefs of Staff is defined by statute and consists of the chairman of the Joint Chiefs of Staff (CJCS), vice chairman of the Joint Chiefs of Staff (VCJCS), senior enlisted advisor to the chairman (SEAC), the Military Service chiefs from the Army, Marine Corps, Navy, Air Force, and Space Force, in addition to the chief of National Guard Bureau, all appointed by the president following U.S. Senate confirmation. Each of the individual Military Service Chiefs, outside their Joint Chiefs of Staff obligations, works directly for the secretary of the military cepartment concerned: the Secretary of the Army, Secretary of the Navy, and Secretary of the Air Force.

Following the Goldwater–Nichols Act in 1986, the Joint Chiefs of Staff no longer maintain operational command authority individually or collectively. The chain of command goes from the president to the secretary of defense to the commanders of the Combatant Commands. Goldwater–Nichols also created the office of vice-chairman, and the chairman is now designated as the *principal military adviser* to the secretary of defense, the Homeland Security Council, the National Security Council and to the president.

The Joint Staff (JS) is a headquarters staff at the Pentagon made up of personnel from all four services that assist the chairman and vice chairman in discharging their duties. It is managed by the Director of the Joint Staff (DJS) who is a lieutenant general or vice admiral.

### Military departments and services

There are three military departments within the Department of Defense:

1. the Department of the Army, within which the United States Army is organized.
2. the Department of the Navy, within which the United States Navy and the United States Marine Corps are organized.
3. the Department of the Air Force, within which the United States Air Force and United States Space Force are organized.

The Military Departments are each headed by their own secretary (i.e., Secretary of the Army, Secretary of the Navy and Secretary of the Air Force), appointed by the president, with the advice and consent of the Senate. They have the legal authority under Title 10 of the United States Code to conduct all the affairs of their respective departments within which the military services are organized. The secretaries of the Military Departments are (by law) subordinate to the secretary of defense and (by SecDef delegation) to the deputy secretary of defense.

Secretaries of military departments, in turn, normally exercise authority over their forces by delegation through their respective service chiefs (i.e., Chief of Staff of the Army, Commandant of the Marine Corps, Chief of Naval Operations, Chief of Staff of the Air Force, and Chief of Space Operations) over forces not assigned to a Combatant Command.

Secretaries of Military Departments and service chiefs do not possess operational command authority over U.S. troops (this power was stripped from them in the Defense Reorganization Act of 1958), and instead, Military Departments are tasked solely with "the training, provision of equipment, and administration of troops."

### Unified Combatant Commands

A unified combatant command is a military command composed of personnel/equipment from at least two Military Departments, which has a broad/continuing mission.

These military mepartments are responsible for equipping and training troops to fight, while the Unified Combatant Commands are responsible for military forces' actual operational command. Almost all operational U.S. forces are under the authority of a Unified Command. The Unified Commands are governed by a Unified Command Plan—a frequently updated document (produced by the DoD), which lays out the Command's mission, geographical/functional responsibilities, and force structure.

During military operations, the chain of command runs from the president to the secretary of defense to the combatant commanders of the Combatant Commands.

As of 2019, the United States has eleven Combatant Commands, organized either on a geographical basis (known as "area of responsibility", AOR) or on a global, functional basis:

* U.S. Northern Command (USNORTHCOM)
* U.S. Southern Command (USSOUTHCOM)
* U.S. Central Command (USCENTCOM)
* U.S. European Command (USEUCOM)
* U.S. Indo-Pacific Command (USINDOPACOM)
* U.S. Africa Command (USAFRICOM)
* U.S. Strategic Command (USSTRATCOM)
* U.S. Special Operations Command (USSOCOM)
* U.S. Transportation Command (USTRANSCOM)
* U.S. Cyber Command (USCYBERCOM)
* U.S. Space Command (USSPACECOM)

## See Also

* United States Department of Homeland Security (DHS)
* United States Department of Justice (DOJ)
* United States Department of State (DOS)