“Radar Contact!”

The Beginnings of Army Air Forces Radar

and Fighter Control

Randall DeGering

Air University Press

Curtis E. LeMay Center for Doctrine Development and Education

Maxwell Air Force Base, Alabama
Project Editor

James S. Howard

Copy Editor

Tammi Dacus

Cover Art and Book Design

Susan Fair

Composition and Prepress Production

Michele D. Harrell

Print Preparation and Distribution

Diane Clark

Library of Congress Cataloging-in-Publication Data

Names: DeGering, Randall, author. | Air University

(U.S.). Press, publisher.

Title: Radar contact : the beginnings of Army Air Forces

radar and fighter control / Randall DeGering.

Other titles: Beginnings of Army Air Forces Radar and

Fighter Control

Description: First edition. | Maxwell AFB, Alabama : Air

University Press, [2018] | Includes bibliographical references and index.

Identifiers: LCCN 2017060452| ISBN 9781585662913

Subjects: LCSH: Radar—Military applications—United 

States—History. | United States. Army. Air Corps—

History. | United States. Army. Signal Corps—History. | 

Radar in aeronautics—History.

Classification: LCC UG612.3 .D44 2018 | DDC 

623.73480973--dc23 | SUDOC D 301.26/6:R 11

LC record available at https://lccn.loc.gov/2017060452

Published by Air University Press in July 2018

Disclaimer

Opinions, conclusions, and recommendations 

expressed or implied within are solely those of the 

authors and do not necessarily represent the official 

policy or position of the organizations with which they 

are associated or the views of the LeMay Center, Air 

University, United States Air Force, Department of 

Defense, or any other US gov-ernment agency. This 

publication is cleared for public release and unlimited 

distribution.

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Air University Press
iii

Contents

Disclaimer ii

List of illustrations v

About the Author ix

Preface xi

 1 Testing an Aircraft Defense Concept 1

Early Air Corps Air Defense Attempts 1

Fort Knox, the First Reporting Net Exercise 5

Fort Bragg, the Proof of Concept 11

 2 The Invention of Radar 17

American “Radio Position Finding” Research

and Development 17

British “Radio Direction Finding” Research

and Development 22

 3 The RAF’s Fighter Control System 27

Air Ministry Experimental Set 1 at Bawdsey Manor 27

The Control and Reporting System 31

The Battle of Britain 36

Introduction of Ground-Controlled Interception 43

 4 The American Aircraft Warning Service Takes Shape 49

The Army Air Defense Command 49

Overseas Air Defense Planning 55

Signal Corps Aircraft Warning Training 58

 5 The Army Air Forces Take Charge 65

First Radars Arrive 65

New Air Defense Mission and Organization 68

Advanced Radar Training 72

Army Air Forces School of Applied Tactics and “Trigger” 74

 6 First Fighter Control Squadrons Emerge 79

Initial Air Defense Deployments 84

Radar and the Attack on Pearl Harbor 90

Conclusion 90

Bibliography 93

v

Illustrations

Figure

 1-1 Capt Claire Chennault, ACTS instructor 2

 1-2 Air Corps Tactical School 3

 1-3 B-10 bombers in 1933 maneuvers 4

 1-4 P-26 pursuit aircraft in formation 4

 1-5 Maj Carl A. Spaatz directs flights with very high

frequency (VHF) radio 6

 1-6 Maj Gen Gordon Saville, first director of air defense 9

 1-7 A-17 attack aircraft 11

 1-8 Ground observation watchtower 13

 2-1 US Naval Research Laboratory 18

 2-2 Early Naval Research Laboratory radar 19

 2-3 SCR-268 short-range radar 20

 2-4 Dr. Robert Watson–Watt 23

 3-1 Bawdsey Manor on the English coast 27

 3-2 RDF operator plotting aircraft on the scope 29

 3-3 Chain Home steel and wooden radar towers 30

 3-4 RDF station reporting aircraft to Fighter Command 30

 3-5 Air Marshal Sir Hugh Dowding 31

 3-6 Operations room 32

 3-7 The Dowding C&R system 34

 3-8 Chain Home coverage, 1939 and 1940 35
vi

Figure

 3-9 Battle of Britain bases 37

 3-10 “Come to readiness!” 38

 3-11 Supermarine Spitfire formation 38

 3-12 British and German dogfight vapor trails 42

 3-13 Rotating GCI radar 44

 3-14 GCI controller and plotters 45

 4-1 Gen Hap Arnold 50

 4-2 Maj Gen James Chaney 51

 4-3 Air defense exercise at Watertown,

New York, 1940 53

 4-4 Air defense exercise at New York City, 1941 54

 4-5 SCR-271 radar station in Panama 56

 4-6 Signal Corps field training class 58

 4-7 Arriving at Fort Monmouth for training 60

 4-8 Marching to class at Fort Monmouth 61

 4-9 Fort Monmouth electronics training 61

 4-10 SCR-270 mobile radar 62

 5-1 SCR-268 mobile radar 66

 5-2 SCR-270 mobile radar 67

 5-3 War Department reorganization, June 1941 71

 5-4 AAF air defense organization 72

 6-1 “Historical Data” 80

ILLUSTRATIONS
vii

ILLUSTRATIONS

Figure

 6-2 Direction finding truck 81

 6-3 Direction finding operator 81

 6-4 Operation plotters charting air tracks 82

 6-5 Philadelphia Information Center (1940) 85

 6-6 SCR-270 mobile radar in Panama 86

 6-7 SCR-268 radar in Greenland 87

 6-8 Opana Radar Station 89

 6-9 Opana radar plot 91

ix

About the Author

In 1990, then a captain, Randall DeGering was the only active duty 

USAF officer to be selected to receive a $1,000 scholarship from the 

Air Force Historical Research Agency (AFHRA) to research the beginnings of radar development and tactical fighter control before 

World War II. He first researched the existing technical literature 

available via universities across the country, this being the pre-Internet 

era, regarding the “science” of radar development both in the United 

States and Great Britain. He then visited the AFHRA at Maxwell AFB, 

Alabama, several times and at personal expense to retrieve many storage boxes of unit histories and review the exploits of various US Army 

Signal Corps units as they developed the early “art” of radar fighter 

control. The result of this long and completely off-duty effort was a 

170-page research monograph delivered to the AFHRA in 1993. Now, 

25 years later, retired Lieutenant Colonel DeGering’s research effort is 

finally available in book form for a much wider audience.

A career air battle manager, he has flown over 2,700 hours aboard 

the E-3 airborne warning and control system (AWACS) aircraft, conducting real-world theater air control operations around the world. 

He currently serves at Headquarters North American Air Defense 

Command as an air defense radar analyst.

xi

Preface

When and how was radar first developed? When was it first employed to direct fighters against approaching enemy aircraft? These 

two questions began the research that serves as the foundation for 

this book.

After being selected for an AFHRA research grant in 1990, three 

years were spent attempting to answer those two primary questions 

using AFHRA’s impressive historical archives collocated with the 

Fairchild Research Information Center at Maxwell Air Force Base, 

Alabama. The AFHRA staff have a tremendous amount of information 

for, and patience with, those new to the world of archival research. 

To put this book in its proper context, this is a story that takes 

place within an Army environment before the beginning of the US 

Air Force. As the history of radar’s research and development unfolds, we will see the Army Signal Corps urgently attempting to develop cutting-edge radar technology. Moreover, as the air defense 

mission grows, we will see the Army Air Corps struggling to define 

its new roles and effectively organize itself.

The term aircraft warning service (AWS) alludes to an organization 

of observers dedicated to providing aircraft sighting reports to a centralized center, which then notifies the nearest aerodrome to have its 

pursuit aircraft immediately take off in hopes of finding the intruder. 

The term service implies a support function, much like the Services of 

Supply or the Chemical Warfare Service. Unlike most Army services, 

however, the AWS was composed of both Army Signal Corps technicians and Air Corps aircraft operators. This dual nature would serve 

as a constant source of frustration to both communities. It is from 

this mixed environment the first fighter control squadrons emerged.

For an Air Force officer completely unfamiliar with either the development of radar or the history of the Army, several sources formed 

the foundation of research:

• Concerning the history of radar development, S. S. Swords’ 

Technical History of the Beginnings of Radar and Radar Development to 1945 edited by R. W. Burns were excellent sources.

• For the Army AWS story, the United States Army in World War II

multivolume “green books” were essential. The volume Guarding 

the US and its Outposts, outlining early air defense efforts, and 

the excellent, three-volume Signal Corps history series, outlining 
xii

PREFACE

radar development and the formation of Signal Aircraft Warning companies, proved to be key resources for research.

• For the Army Air Forces viewpoint, the excellent Army Air 

Forces in World War II multivolume “blue books,” particularly 

the first volume, Plans and Early Operations, covered early air 

defense deployments.

• There are many unit histories and reports written during and 

shortly after World War II, all of which are on file in the AFHRA, 

to build on these foundational volumes. All that is needed is 

weeks and weeks to read them!

Overall, this project was a fascinating exercise at its best—a frustrating project at its worst. Research was constantly caught, back and 

forth, between the Army “green books”—that include a separate Signal Corps series—and the Army Air Forces “blue books.” Likewise, 

since radar air defense and fighter control appear in both green and 

blue books, neither is covered well in either series.

The hope that one day this book might be published and the story 

of the beginnings of radar and tactical fighter control would become 

available and, hopefully, enjoyed by the air battle managers that follow propelled the research and writing. What this book clearly shows 

is what air battle managers do today has its foundations in procedures and terminology developed by bold and innovative people over 

80 years ago. It is also important to know and appreciate our proud 

fighter controller heritage.
Chapter 1

Testing an Aircraft Defense Concept

Early Air Corps Air Defense Attempts

In 1932, the War Department established four continental field 

armies to better carry out its United States continental defense responsibilities. First United States Army was charged with defending 

the United States’ eastern seaboard, Second United States Army was 

responsible for defending the Pacific Northwest region, Third United 

States Army was to defend the Gulf of Mexico coastline, and Fourth 

United States Army was to protect the Southwest border.1

Also, each of these field armies included a new air district for aviation support. During the 1930s neither the air districts nor the Air 

Corps had formal systems of aircraft ground control. While the British had developed an ingenious air defense observation system to 

protect the city of London during World War I, the American Air 

Corps was not concerned with developing an air defense strategy. 

British air defense had reached its apex with the formation of the 

London Air Defence Area (LADA). In a central control room, a large 

map was surrounded by plotters wearing headphones and in contact 

with observation posts surrounding the city of London. Whenever a 

German zeppelin flew over the country, its position was reported every half-minute to the plotters, who marked out the raider’s path on 

the map. The control room then issued air raid warnings and orders 

to antiaircraft brigades surrounding the city. Thus, by war’s end, there 

existed a complex air raid warning organization, with the London 

area well defended. Like all observation networks, however, it was 

only effective in the daytime. It also suffered from observer errors 

and was useless in fog or heavy cloud cover. For its time LADA was 

the most complex area air defense system yet devised, and its fundamental design and operation would be copied by all ground control 

systems that followed.2

The Americans were developing a new air doctrine emphasizing 

the invulnerability and importance of strategic air bombardment. 

Consequently the pursuit mission was discounted. Lt Kenneth 

Walker, an aerial bombardment instructor at the Air Corps Tactical 

School (ACTS) at Maxwell Airfield, Alabama, stated: “Military airmen 
2 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

of all nations agree that a determined air attack, once launched, is 

most difficult, if not impossible to stop.”3

 Pursuit aviation was considered superfluous. Also, there seemed to be no need for escort aircraft 

for bomber formations—the “no escort” position.

As strong as the proponents of bombardment aviation were, there 

were a few pursuit activists. Perhaps the most outspoken of these during the 1930s was Capt Claire Chennault (fig. 1-1), a pursuit instructor 

at ACTS (fig. 1-2). Chennault described the frustrations of pursuit operations then being employed by the Air Corps:

The warning system then in vogue was a loose network of spotters who reported vaguely by telephone. . . . Normal orders to defense fighters went something like this: “Enemy bombers reported over Point X at 9 A.M. Take off and 

destroy them.” It would then be 9:15, and X was twenty miles away. When we 

flew to X and returned after failing to sight any bombers, it was accepted as 

undeniable proof that fighters could not intercept modern bombers.4

Figure 1-1. Capt Claire Chennault, ACTS instructor. (Reprinted from 

https://commons.wikimedia.org/wiki/File:Capt._C.L_Chennault,_leader_

of_The_Flying_Trapeze_poses_in_front_of_a_Boeing_P-12E.jpg.)
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 3

Figure 1-2. Air Corps Tactical School. (Reprinted from https://en.wikipedia.org/wiki/Air_Corps_Tactical_School#/media/File:A_Concise_

History_of_the_U.S._Air_Force_Page_14-1.jpg, Stephen A McFarland, 

A Concise History of the US Air Force [Washington, DC: Air Force History and Museums Program, 1997], 14.)

Later, in his memoirs, Chennault would look back on this early 

period and remark:

The speed and armament of the Martin B-10 bomber [fig. 1-3] matched 235 

miles per hour and five guns against the 225 miles per hour and two guns of the 

Boeing P-26 [fig. 1-4], then the standard Army and Navy fighter. The neglected 

field of fighter tactics, together with the total lack of any means for obtaining 

information about the enemy and tracking his airplanes, made the contest even 

that more unequal . . . . Biggest problem of modern fighters was intelligence. 

Without a continuous stream of accurate information keeping the fighters 

posted on exactly where the high-speed bombers were, attempts at interception 

were like hunting needles in a limitless haystack.5
4 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

Figure 1-3. B-10 bombers in 1933 maneuvers. (Reprinted from Kohn 

and Harahan, eds., Air Superiority in World War II and Korea. [Washington, DC: Office of Air Force History, 1983], 20, https://media.defense.

gov/2010/May/25/2001330267/-1/-1/0/AFD-100525-068.pdf.)

Figure 1-4. P-26 pursuit aircraft in formation. (USAF photo: http://www.

nationalmuseum.af.mil/Upcoming/Photos.aspx?igphoto=2000543703.)
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 5

Unfortunately for Chennault, the early 1930s Air Corps air defense exercises reinforced the “unstoppable” bomber theory. The 

1931–33 Pacific Coast maneuvers conducted from March Field, California (located east of Los Angeles), were described by Chennault:

Later, “Hap” Arnold, then a lieutenant colonel, ordered squadrons of Martin 

B-10s from San Diego in an attack on March Field. Defending fighters at 

March Field took off according to strict military protocol. There was no vulgar 

scramble. Flights formed over the field and merged into squadrons. Squadrons then circled until the group commander took off and joined them to lead 

the formation. By that time the bombers had delivered their attack and departed. Only a few independent fighters, stationed at an outlying refueling 

field, made an interception. They scrambled into the air immediately on receipt of warning without benefit of protocol. Arnold concluded from these 

maneuvers that fighters would be ineffective in wartime.6

Fort Knox, the First Reporting Net Exercise

A joint Army antiaircraft artillery–Air Corps exercise was conducted in May 1933 at Fort Knox, Kentucky, including, for the first 

time, an attempt at ground control of pursuit aircraft using an organized aircraft reporting network. In the exercise, a line from Indianapolis to Cincinnati divided two warring states, Blue to the north, 

Red to the south. The Blue’s bomber force was based at Patterson 

Field, Ohio. It included Curtiss B-2s, Douglas B-7s, and Boeing B-9s 

from March Field and Langley Field, Virginia. The Red air forces, 

consisting of Curtis P-6s and Boeing P-12s, were stationed at Bowman Field, Kentucky, 26 miles from Fort Knox, representing a rail 

and supply center to be defended.7

This first American attempt at an air defense system was impressive. The intelligence network (or net) consisted of 69 observation 

posts covering an area of approximately 1,600 square miles. It was 

shaped in the form of a 120-degree angle facing Ohio, with the apex 

at Fort Knox. The reporting net was established by the Army’s Signal 

Corps, while observation posts were manned by soldiers from the 

various ground force branches. Observers had little instruction and 

experience in identifying aircraft by type and were provided with no 

instructions for the calculation of altitude or courses. Altitudes were 

to be simply reported as either “low,” “high,” or “very high.”

During the exercise, reports from these posts were made to the air 

defense headquarters at Fort Knox, which then immediately relayed 
6 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

the information to the pursuit group operations office at Bowman 

Field. The group commander would order his aircraft into the air, 

transmit information as to the latest observation of the enemy forces 

to his flyers, and direct his aircraft as necessary to keep them between 

the approaching enemy and their Fort Knox target (fig. 1-5).

Figure 1-5. Maj Carl A. Spaatz directs flights with very high frequency 

(VHF) radio. (Reprinted from http://media.defense.gov/2010/Sep/23/20013

30114/-1/-1/0/AFD-100923-007.pdf, Mauer, Aviation in the US Army, 234.)

The results of this first effort at ground control of pursuit aircraft 

were mixed. Chennault pointed out several of the inadequacies of the 

system used in the exercise:

The bands of observation-listening posts were approximately twenty-five 

miles apart. Hostile bombardment and attack could (and did) change course 

between bands . . . preventing pursuit from consistently making point interceptions on the enemy’s line of flight.

The information net ended at an average distance of about sixty miles from 

the defended point. Pursuit was forced to make its interception upon information furnished by the inner band of the net. This condition required some 

unit of pursuit force to be in the vicinity of all the stations on the inner band 

at the moment the final reports were received. . . .

It did not furnish pursuit with accurate estimates of the type, numbers, course, 

and altitude of the hostile force. These inaccuracies forced pursuit to search 
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 7

much greater areas in space than would have been necessary if accurate reports had been furnished.8

Despite these shortfalls, Chennault maintained that “its operation 

enabled pursuit to make a far greater percentage of interceptions than 

having ever before been accomplished in any maneuvers.”9

Using the 1933 Fort Knox exercise as his model, in 1935 Chennault developed his celebrated paper entitled The Role of Defensive 

Pursuit. He reviewed the background of pursuit development and 

analyzed the causes for pursuit’s failure as an effective weapon. He 

theorized that providing a means for the timely collection and transmission of accurate, continuing information of the hostile force was 

the key to pursuit’s ability to make effective interceptions. The key 

elements of his theory were:

• First, that an effective pursuit force cannot be maintained airborne at all times.

• Second, that attacking forces must be intercepted at such distance from the defended point to permit destruction of the attackers before they arrive over their target.

• Third, that timely information must be provided to pursuit concerning the approach of the hostile force.

• Finally, that the information must be transmitted to a central 

authority, evaluated, and acted upon. Changes in strength, 

course, altitude, and disposition must be continuously reported 

as they occur.10

At this point, probably the single greatest factor in the lack of 

timely aircraft ground control was the crude state of radio communications technology. Instructors at ACTS realized this deficiency in 

their texts:

The difficulty of control during air combat is occasioned by the existence of 

the very conditions necessary for the accomplishment of flight. The noise of 

the engine and propeller, coupled with the necessity of continuous movement, 

almost eliminates the possibility of control through the usual auditory means. 

Lack of adequate communications is probably the greatest stumbling block in 

the development of air tactics.11

However, in 1935, improved super-heterodyne technology in VHF 

receivers increased their range and reliability, thereby improving communications between pursuit aircraft and the ground. It is probably 
8 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

fair to conclude that Chennault’s theory of ground control of aircraft 

would not have developed without this new, reliable, means of 

ground-to-air communications. 

With this new technology, Chennault outlined two choices for collecting and disseminating accurate, timely information at frequent 

intervals:

• observation aircraft or

• a ground intelligence network. 

The advantages to aerial observation were offset by three disadvantages:

• observation aircraft were vulnerable to hostile aircraft, 

• airborne surveillance might prove costly to maintain, and 

• limitations could be imposed by weather conditions.

As envisioned by Chennault, a ground intelligence network appeared to be much more promising. It would use a large number of 

civilian and military observers located far from the vital area to be 

defended. Observers would report to a central command post using 

existing civilian telephone or telegraph equipment. Continuously updated observer information could be transmitted to pursuit aircraft 

with a powerful command post radio. The large personnel and equipment requirements were not overwhelming disadvantages in Chennault’s view.

Chennault also clearly addressed the problems of command and 

control over this pursuit force. Identifying a fundamental tenet in airpower employment, he stated:

Action upon information of the hostile aerial force can be directed only by the 

central authority, who should have under his command and control the means 

for collecting and evaluating information, and the means for opposing the 

invasion of the hostile force . . . . The central authority should be the commander of the air force responsible for the aircraft defense of the point or area. 

It is certain . . . that any division of authority in the central command will result in loss of invaluable time and ineffective aerial operations.12

The concept of air defense failed to stimulate the level of intellectual discussion that a more glamourous theory of precision strategic 

bombardment had attracted. Nevertheless, Chennault’s concern for 

the proper employment of pursuit aircraft did not go unheard. Upon 

his leaving ACTS in 1935, Chennault was replaced with another pursuit enthusiast—Capt Gordon P. Saville (fig. 1-6). During his tour at 
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 9

ACTS, Saville became more and more interested in air defense. Unlike 

Chennault, he did not dispute the dominance of the bomber as an 

offensive weapon but rather focused purely on the defensive functions of pursuit.

Figure 1-6. Maj Gen Gordon Saville, first director of air defense. (Reprinted from Schaffel, The Emerging Shield, 44.)

The Florida Air Corps maneuvers of 1935 brought together these 

various new elements of early warning and ground control for the 

first time. In a bold change, Saville proposed shifting the command of 

the pursuit formation from the cockpit to the ground, arousing strong 

opposition.13 The commander of the 2nd Wing, Brig Gen H. Conger 

Pratt, completely supported Saville in a postexercise critique.14 Pratt 

concluded that ground control had exercised better command of the 

P-26 pursuit assets because the ground controllers had more and better information that was not immediately available to the individual 

airborne pursuit formation commanders. “The entire system is predicated on ground control at all times. When that command is interrupted or assumed by others, the system is immediately susceptible 

to failure.”15 In response, the ACTS pursuit texts now began incorporating Chennault’s and Saville’s visionary air defense concept into 
10 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

what was labeled as the aircraft reporting net (ARN) and calling it the 

“best solution to the problem of defense.”16

According to this new ACTS doctrine, the ARN was to be organized over an area inside a circle with a radius of approximately 125 

miles. Ground observer stations were to be located about every eight 

miles within this circle and were to report to a control center by direct wire, using a grid coordinate system. As the progress of the hostile aircraft was plotted at the control center, ground control would 

make decisions concerning the use of antiaircraft artillery (AAA) or 

pursuit aircraft against the intruders based upon the reported tactical 

situation. Interceptor aircraft were to be under ground control, who 

directed them to intercept the attackers.

Responding to the results of the Florida Maneuvers, the War Department issued a new and significant directive on air defense to the 

four field army commanders in May 1935. It tasked the field armies’ 

air districts to begin preparations for an integrated air defense effort 

consisting of aviation, AAA, and a new aircraft warning service 

(AWS) for defense against coastal air attacks.17 The War Department 

directive was the first official reference to a formal AWS organization 

and was probably viewed as a natural successor to the extant Antiaircraft Artillery Intelligence Service.18

In May 1936, the Air Corps held another air defense exercise. Flying 

out of Muroc Dry Lake, just east of Los Angeles, about 300 bombers 

flew practice bombing missions against the city during the month. Air 

defense aircraft were launched out of March Field. Recalling those maneuvers, then Flying Cadet James Ferguson (who later became commander of Air Force Systems Command) remembered their difficulties:

The Muroc Lake maneuvers in 1936 simulated a fighter defense of a metropolitan area—in this case Los Angeles and nearby parts. We, the fighters, were the 

defenders flying Boeing P-36s. The attacking forces were equipped with B-10 

bombers and A-17 attack aircraft [fig. 1-7]. The bombers came in on the attack 

too high for us to reach them, and the attackers used terrain masking to surprise 

us on the ground. With no other means of warning, we were caught and treated 

to a good dose of tear gas which took weeks to shake out of our blankets.19

After the Muroc Lake maneuvers, it was now clear that effective 

warning and control of pursuit aircraft to their bomber targets were 

critical to the success of air defense. An effective ARN would seem to 

be the key, but it had never been realistically tested. Could it be made 

to work?
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 11

Figure 1-7. A-17 attack aircraft. (Reprinted from Kohn and Harahan,

eds., Air Superiority in World War II and Korea [Washington, DC: Office 

of Air Force History, 1983], 24, https://media.defense.gov/2010/

May/25/2001330267/-1/-1/0/AFD-100525-068.pdf.)

Fort Bragg, the Proof of Concept

In October 1938, the War Department conducted an ambitious joint 

Army AAA–Air Corps exercise in eastern North Carolina, around Fort 

Bragg. For the first time in a major Army exercise, the following air defense ground-control-related objectives would be included:

1. To devise methods for coordinating the action between the Air 

Corps, AAA, and the Aircraft Warning Service (AWS) in the 

defense of an air base against attack by “hostile” aviation, including control measures necessary to prevent antiaircraft artillery firing on friendly aircraft operating within the defended 

area.

2. To test the practicability of organizing an AWS utilizing nonmilitary personnel as observers, as contemplated by frontier 

defense plans.
12 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

3. To test the comparative efficiency of military and nonmilitary 

personnel as aircraft warning observers.

4. To test the ability of ground observers to detect and determine 

the types of aircraft flying over their respective positions at various times by day and by night.20

For the exercise, Black air forces consisted of three bombardment 

squadrons, one each of Martin B-10s, Boeing B-17s, and Douglas B-18s, 

and an attack squadron of Northup A-17s. Based at Langley Field, 

Black forces were to fly out over the sea and come back over the 

coastline, representing hostile planes launched from aircraft carriers. 

Blue forces were to defend the airdrome at Fort Bragg and comprised 

two squadrons of Consolidated P-30 and a single squadron of Seversky 

P-35 pursuit fighters, all flying out of Pope Field.

The War Department’s planning guidance for the exercise directed 

the establishment of an AWS over an area consisting of 39 rural counties in eastern North Carolina. Lacking enough Officers’ Reserve 

Corps (ORC) officers to man the “Net,” volunteers were identified 

through the cooperation of local newspapers, the American Legion, 

and other civic organizations. The few ORC officers who were available manned the 47 US Forest Service fire watchtowers within the 

grid (fig. 1-8). Local civilian interest was so strong that in practically 

every instance, each community near a fire watchtower insisted on 

furnishing additional civilian observers to assist the ORC officers. In 

fact, in one or two cases, they requested ORC officers not be assigned 

so they could furnish all the observers.21

In addition to the civilian observers, the commercial telephone 

companies provided tremendous support for the exercise. The Carolina Telephone and Telegraph Company assumed responsibility for 

coordinating all the activities of the 15 independent telephone companies in the grid area. Telephone company personnel were trained 

in “flash” procedures for sending priority observation messages to the 

sector message center in minimum time.
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 13

Figure 1-8. Ground observation watchtower. (Reprinted from http://

www.hampton.lib.nh.us/hampton/history/military/homefront/WWIIwatchtower.htm, Official Signal Corps photo.)

An innovation of this exercise was the map room, established for 

observers and members of the press to keep up with the exercise’s 

situation. A large, 8-foot by 16-foot map was displayed, which used 

individual lights to indicated each observer station. Loudspeakers 

were installed so that all might hear each critical “flash” message as it 

was transmitted by an observation station, while a red light indicated 
14 │ TESTING AN AIRCRAFT DEFENSE CONCEPT

which observer station had just made that report. Pursuit squadron 

alert orders, launch orders, and interception vectors were heard 

through the pursuit commander’s loudspeaker. Green lights indicated 

the presence of friendly aircraft observed in an observation grid while 

flashing green lights indicated the “enemy” interceptions. There was 

also a speaker sounding the brigade command post on Gaddys 

Mountain orders directing spotlights and antiaircraft guns.22

In his after-action report, the AWS commander was proud of the 

accomplishment of his military/civilian warning force. During the 

week of 10–15 October 1938, approximately 1,800 individuals were 

employed in over 300 observation posts, and not a single “enemy” 

aircraft passed overhead without being reported. Also, the pursuit 

commander praised the warning net, saying that it had functioned 

much better than expected. Finally, the overall defense commander 

stated, “It has shown that an effective Aircraft Warning Net is necessary 

to enable pursuit to make interceptions in the daytime.”23

In a letter to ACTS in 1939, the War Department presented its official views on the exercise. Conclusions reached in Washington relating to ground control of pursuit aviation included:

1. The establishment of an efficient AWS is practicable . . . .

2. An efficient AWS is essential to the effective employment of defending pursuit aviation . . . .

3. Coordination of pursuit and AAA activities during daylight is 

practicable. The problem of such coordination during darkness 

has not been solved.24

Overall, the employment of pursuit in conjunction with a warning 

net had proven to be surprisingly efficient. The bottom line from the 

ACTS was that “the school theory of a coordinated defense, which 

includes pursuit, antiaircraft artillery, and the interception net . . . was 

proved sound.”25

Although overshadowed by the importance of bombardment aviation in the early 1930s, pursuit’s acceptance within the Air Corps 

made steady progress throughout the rest of the decade. To survive 

the bomber air defense challenge, pursuit aircraft needed ground 

control. Moreover, clearly, the effectiveness of pursuit was in direct 

proportion to the efficiency of that ground control’s structure and 

observer corps.
TESTING AN AIRCRAFT DEFENSE CONCEPT │ 15

Still in its infancy, this newly-devised concept of an AWS would 

soon mature into a critical warfighting system—but it would fall to 

the British Royal Air Force (RAF) to make it happen. While the 

American Army Air Corps celebrated its modest peacetime exercise 

success, the British RAF was secretly building its massive operational 

air defense network while watching a determined Nazi Germany rearming for war. Moreover, unknown to Chennault and Saville, the 

British had solved their problems of observation using a new and extremely secret method called “RADAR.”

Notes

1. Conn, Engelman, and Fairchild, Guarding the United States, 17. 

2. Swords, ed., Technical History, 176–8.

3. Greer, Development of Air Doctrine, 56. 

4. Chennault, The Way of a Fighter, 22. 

5. Ibid.

6. Ibid.

7. Mauer, Aviation in the US Army, 415.

8. Chennault, Role of Defensive Pursuit, 35–6.

9. Ibid., 36.

10. Ibid., 16–18.

11. Air Corps Tactical School (ACTS), Pursuit Text, 166.

12. Chennault, Role of Defensive Pursuit, 20. 

13. Schaffel, Emerging Shield, 14. 

14. One of the original wings of General Headquarters Air Force, 2nd Wing was 

discontinued in 1942 and has no connection with the current 2nd Bombardment Wing.

15. Ibid., 15–6. 

16. ACTS, Pursuit Aviation, 69. 

17. Conn, Engelman, and Fairchild, Guarding the United States, 54. 

18. Terrett, Emergency, 135.

19. Kohn and Harahan, Air Superiority, 26. 

20. ACTS, Report of the Defense Commander, 1. 

21. ACTS, Annex 3, 7. 

22. Ibid, 8.

23. ACTS, Report of the Defense Commander, 15.

24. ACTS, Annex 2, 2.

25. ACTS, Study of the Reports, 6.

Chapter 2

The Invention of Radar

American “Radio Position Finding”

Research and Development

The basic principle of radar detection is almost as old as the subject 

of electromagnetism itself. Heinrich Hertz, in 1886, tested the theories 

of James Maxwell and demonstrated that radio waves could be “reflected” by metallic and dielectric bodies. Guglielmo Marconi recognized the potentials of short waves for radio detection and strongly 

urged their use in 1922 but was apparently unsuccessful in gaining support for this idea. Also, during the 1920s, much discussion occurred 

concerning the use of radio detection methods aboard ships to avoid 

collisions, but these topics received limited government interest.1

The first detection of aircraft using experimental continuous wave 

(CW) equipment was in June 1930 by Lawrence Hyland, Albert Taylor, 

and Leo Young of the US Naval Research Laboratory (NRL) near 

Washington, DC (fig. 2-1).2

 It was made accidentally while testing a 

radio direction-finding device located in an aircraft parked on the 

grounds of nearby Bolling Field. While receiving signals from a transmitter located two miles away, Hyland noticed the transmitter’s signal 

seemed to appear from other directions whenever random aircraft 

happened to pass overhead their parked airplane—in effect, reflecting the transmitter’s signal back to Hyland’s receiver. This discovery 

stimulated a more deliberate investigation by the NRL, but the work 

continued slowly due to the lack of official support and funds from 

the US government.

However, by 1932, equipment had been developed by the NRL that 

could detect aircraft at distances up to 50 miles. At this point, it is 

important to note, however, that CW equipment could only detect 

the presence of a distant target. The problem of determining a target’s 

position—that is, its bearing and range—was a difficult one and could 

not be readily solved with then-current technology. The NRL’s work 

on aircraft detection with CW signals was kept classified until 1933, 

at which point several Bell Telephone Laboratories engineers reported 

the detection of aircraft by radio means during other experiments. 

Realizing the confidentiality of their work had now been compromised, 
18 │ THE INVENTION OF RADAR 

the NRL then disclosed its work.3 A US Patent (No. 1981884) was 

granted to Hyland, Taylor, and Young for “A System for Detecting 

Objects by Radio” on 27 November 1934.

Figure 2-1. US Naval Research Laboratory. (Reprinted from https://

commons.wikimedia.org/wiki/File:US_Naval_Research_Laboratory_

in_1944.png, US Navy photo.)

The limited ability of CW equipment to be anything more than a 

trip wire, providing only general range data about a target, explains 

the little official US enthusiasm that existed for future research. Having spent three years on this method, the NRL also recognized this 

limitation and realized that to obtain accurate target position information, energy had to be transmitted in pulses that could be timed 

and measured. Thus, a new NRL effort was started by Robert Page in 

spring 1934 on pulsed energy transmission and measurement.

After nearly two years of working and reworking his designs, in 

April 1936 Page’s pulsed transmission equipment first successfully 

detected an aircraft at about 2.5 miles of range.4

 It operated at 28.2 

megahertz, with a peak power of over 3 kilowatts, a pulse width of 

5–7 microseconds, and a pulse repetition frequency of about 1,800 

cycles per second. Further improvements were made, and by November 

1936, aircraft as far as 36 miles were being successfully detected (fig. 2-2).
THE INVENTION OF RADAR │ 19

Figure 2-2. Early Naval Research Laboratory radar. (Reprinted from 

https://commons.wikimedia.org/wiki/File:Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg, a 1945 issue of Radio News.)

Throughout the course of this naval radio detection research during 

the 1930s, the US Army Signal Corps maintained a similar interest. 

The Corps was responsible for developing all Army signals equipment, such as radio and wire communication sets, and for training all 

Signal Corps personnel to operate such equipment. The beginning of 

serious Signal Corps work in pulsed detection apparently resulted 

from a visit to NRL in January 1936 soon after Page’s first pulsed detection demonstration.5

 While research at NRL was conducted over a 

broad spectrum of interests, the efforts of the Signal Corps Laboratories (SCL) at Fort Monmouth, New Jersey, were geared toward the 

more narrow development of specific pieces of Army equipment. 

Thus, while there was no additional funding allocated by the War 

Department, by May 1936 “pulsed-echo detection” research had received a high priority at the Army lab.

On 14 December 1936, equipment loaded on two trucks (one for the 

transmitter and one for the receiver) set out for a site near Princeton to 
20 │ THE INVENTION OF RADAR 

monitor traffic in and out of Newark airport, parking one mile apart. 

There SCL engineers saw the device record the echoes of the pulses 

directed toward the flight path of arriving and departing airliner traffic. Crude and experimental as it was, and only able to track aircraft 

out to seven miles, it was, nevertheless, the first successful Signal 

Corps pulse radar.6

The turning point for US radar development occurred on 18 May 

1937, when the Secretary of War, Hines Woodring; the Chief of the Air 

Corps, Maj Gen Oscar Westover; and several US senators and representatives attended a classified night demonstration held at the SCL. 

Successfully detecting 13 out of 15 aircraft travelling above 6,000 feet, 

the new detection equipment was used to illuminate each target aircraft using a searchlight. Impressed by this amazing achievement, Secretary Woodring wrote a congratulatory letter to both the Chief Signal 

Officer and President Franklin Roosevelt and asked if $200,000 (equal 

to $3.5 million in 2018 dollars) would be sufficient for further research.7

This experimental set was soon to become the US Army’s first operational radar set, the Signal Corps Radio (SCR) 268 (fig. 2.3). A mobile, 

short-range, height finding set, the SCR-268 was designed primarily to 

be used as a searchlight director and AAA gun-laying radar.

Figure 2-3. SCR-268 short-range radar. (Reprinted from George Raynor 

Thompson, Dixie R. Harris, Pauline M. Oakes, and Dulany Terrett, US 

Army in World War II: The Technical Services: The Signal Corps: The Test

[Washington, DC: Office of the Chief of Military History, 1957], 376, 

http://www.history.army.mil/html/books/010/10-17/CMH_Pub_10-17.pdf.)
THE INVENTION OF RADAR │ 21

The day after it had been successfully demonstrated, the prototype 

SCR-268 was disassembled and secretly moved from SCL to nearby 

Fort Hancock on Sandy Hook, New Jersey.8

 Its antenna was mounted 

atop an adjacent lighthouse station on the beach at Navesink, overlooking the heavily traveled air routes crossing New York Bay into 

Newark and New York City. From here, redesigning and testing continued. The 62nd Coast Artillery Regiment (Antiaircraft), also stationed at Fort Hancock, not only guarded the secret site but helped 

operate the unique equipment. The unit represented the typical 

skilled enlisted man who would eventually actually operate the new 

detector, and their efforts to resolve its many technical problems 

proved invaluable.

Also impressed with the demonstration was Brig Gen Henry 

“Hap” Arnold, assistant chief of the Air Corps. He proposed, in June 

1937, an operational specification for a long-range detection and 

tracking radar specifically for Air Corps use, capable of detecting aircraft at a range of 50 miles, later increased to 120 miles.9

 The next 

month, the technical characteristics required by the Air Corps for 

this new long-range, early warning radar set were formally approved 

by the Army Signal Corps. And by October 1938, a contract was 

signed with the Westinghouse Electric Corporation to assist the Signal 

Corps with additional pulse radar research and development.

Greater detection range was the prime concern of the Air Corps, 

rather than greater equipment mobility, which was desired by Army 

ground antiaircraft crews. Therefore, by June 1938, the work at the 

Fort Hancock site had now been split into two camps: one completing the work on the short-range SCR-268, and one beginning research on a new, long-range, early warning prototype—the SCR-270, 

a trailer-mounted version, pulled by a truck, and the SCR-271, a 

fixed-site version of the SCR-270. By August, a preliminary SCR-270 

model detected a bomber at 75 miles.10

In November 1938, the Army service tests began on the SCR-268 

at Fort Monroe, near Langley Field, Virginia. While not as accurate as 

hoped for, during one night service test, a target Martin B-10 bomber 

was blown off course by 100 mph winds without realizing it. After 

reaching 60 miles out to sea, the pilot surrendered to the urgent 

warnings of the SCL engineers, who had him exactly plotted on their 

oscilloscope and who guided the aircrew safely back to their field—

the first recorded save of an aircraft by radar!11 About the SCR-268, it 

was said that:
22 │ THE INVENTION OF RADAR 

Nobody liked it very much but everyone wanted it badly. . . . Its performance 

was satisfactory for pointing searchlights, although it was considered too 

bulky. It was not quite accurate enough for precision [AAA] gun laying, but it 

was the only available American set that permitted an effective antiaircraft 

barrage through overcast. Its power gave it greater range than necessary for 

either of these . . . purposes, but not quite enough . . . for . . . early warning.12

The SCR-268 transmitted on 205 megahertz, producing wavelengths 

nearly nine feet long, and thus requiring a huge antenna. Having reduced the antenna size down as far as possible, the SCR-268—with its 

limited mobility—was declared wartime ready for US Army operational use in May 1939.

In December 1939, again with Woodring and General Arnold observing, the mobile, long-range SCR-270 set began its certification 

tests at Fort Hancock. Six months later, in May 1939, the US Army 

officially adopted it as its first early warning pulsed-echo radar set.13

Originally, this method of detecting aircraft by radio means was labeled by the Army as “radio position finding” or RPF.14 In addition, 

for the next several years, for security reasons, it would also be referred to as “Radio-B” or the mystifying nickname “Derax.” Later, 

however, in January 1942, the US Navy officially began designating 

its detection systems with the name “RADAR” for radio detection 

and ranging, and this new name was soon universally adopted.15

Across the Atlantic, however, it was a very different story. For by this 

time, the British Royal Air Force (RAF) was already far ahead of the 

work in radar research and development (completely unknown to 

their Allies) and were desperately hurrying to finish the world’s most 

advanced, radar-based air defense system—before it was too late.

British “Radio Direction Finding”

Research and Development

Radar emerged more rapidly in the United Kingdom in the mid1930s because of the country’s vulnerability to direct air attack from 

the nearby continent. By 1934 the British knew that Hitler was building 

up Germany’s air force, the Luftwaffe, and was aiming for nearly 

4,000 bombers—easily capable of overwhelming the RAF’s 600 fighters.16 Also, the summer RAF air exercises of 1934—virtually identical 

to the US Air Corps exercises conducted in 1931–1932—underlined 

the fact that Britain was almost completely defenseless against air assaults. 
THE INVENTION OF RADAR │ 23

The RAF pilots simply could not find incoming bombers in the vast 

sky. During daylight raids, 50 percent of the “hostile” bombers were 

not intercepted.17 A realization of this fact by RAF officers, Air Ministry civil servants, and politicians generated mounting pressure to 

develop a solution, and very quickly.

In January 1935, the Air Ministry hosted the first meeting of the 

Committee for the Scientific Survey of Air Defence, chaired by Henry 

Tizard, then also chairman of the government’s Aeronautical Research Committee. The possibility of using electromagnetic radiation 

to damage aircraft or to incapacitate its aircrew was discussed at this 

first meeting. An unpredictable Scotsman named Robert Watson–

Watt, superintendent of the Radio Research Station, was asked by 

Tizard’s committee to research this futuristic option (fig. 2.4). 

Figure 2-4. Dr. Robert Watson–Watt. (Reprinted from https://commons.wikimedia.org/wiki/File:Robert_Watson-Watt.jpg, Air Ministry, 

United Kingdom, photo.)

Watson–Watt, in his famous February 1935 memorandum entitled “Detection and Location of Aircraft by Radio Methods,” concluded that a “death ray” was not feasible but that shortwave radio 

illumination, using a pulse method, might be used for the detection 

of aircraft. Completely unfamiliar with the NRL’s then-secret research 
24 │ THE INVENTION OF RADAR 

on this very same concept, his memorandum urged that Britain ring 

its shores with “an invisible curtain” of radio waves:

So, said the memorandum, you must set up, in the region through which [an 

aircraft] must pass to reach us, an invisible curtain of short radio frequency 

waves. He cannot prevent some small faction of this radio energy being reflected back, more or less toward its source, as a radio “echo” from his craft. If 

we pick up even a minute fraction of this echo, we can make it tell us a lot 

about him . . . so, said my memorandum in effect, give us the job and we will 

finish the tools, and we shall be surprised if we can’t track a single aircraft 

from 200 miles away.18

Events moved rapidly after this memorandum was issued. During 

the same month, as a test, Watson–Watt’s team positioned a receiver 

near the British Broadcasting Company’s shortwave station at Daventry, 

75 miles northwest of London, and flew a RAF Hadley Page Heyford 

bomber up and down the transmitter’s beam. The objective was to 

attempt to detect any fluctuations in the receiver’s signal caused by 

reflections from the bomber, which would show as “blips” on an oscilloscope. This was the same effect noted earlier by the NRL, which had 

just been granted its now unclassified CW radar patent—too soon to 

have come to the attention of the British scientific community. The 

bomber test was a success, detecting the aircraft out to a range of about 

eight miles.19 This satisfied RAF Air Vice-Marshal Sir Hugh Dowding, 

the Air Ministry’s Air Member for Supply and Research, who then 

granted £12,300, equal to almost $800,000 in 2018, for a large-scale 

experimentation during the rest of 1935.

In May 1935, in a race against time, Watson–Watt’s team (numbering only six people, and working in utter secrecy) moved their operations to Orford Ness, an isolated, sandy isthmus on the wind-swept 

eastern coast of England. The focus now was on developing a working pulse transmitter, operating at a low frequency of 6 megahertz, 

with a wider pulse length of about 15 microseconds, at a pulse repetition frequency somewhere between 50 and 1,000 cycles per second, 

and having a peak pulse power of about 50 kilowatts. The brilliant 

team was soon successful.

By the end of the month, the first pulse radar echoes were being 

successfully bounced off the ionosphere by Watson–Watt’s team—

very close to Page’s original radar specifications—except for the much 

higher power needed to cross the English Channel—and secretly accomplished almost a year earlier than Page’s first successful pulse radar tests at NRL in April 1936.
THE INVENTION OF RADAR │ 25

By July 1935, RAF aircraft were being tracked from Orford Ness 

out to a range of 34 miles.20 The number of aircraft that were flying in 

formation was also being correctly counted. One of the test engineers 

would later remember those research flights and write:

Security was of the maximum category. We did not advertise that any secret work 

was in progress by enclosing the site in barbed wire with sentries on the gate. The 

pilots were not told anything of the work. It was at the time when the pilots 

handed in their flight logs that we had to be extremely careful what we said. We 

wanted to be as open as possible and talk with the chaps who were working with 

us. On one occasion, we realized that we asked one question too many, and had 

to alter the line of the conversation very quickly but smoothly. It became evident 

that the slip had not been noticed and so we relaxed once again.21

This experimental pulse method was labeled by Watson–Watt’s team 

as “radio direction finding” or RDF. This name was considered suitably confusing since it suggested an aircraft navigation method instead of being a method of aircraft detection.

Thus, in September 1935 with the secret RDF research now moving at a rapid and successful pace, Watson–Watt drafted a plan to the 

Tizard committee formally proposing that a “chain” of early warning 

RDF stations be built along the eastern coast of England to provide 

detection and tracking of enemy aircraft off the British shores. Even 

though no actual prototype RDF station yet existed, the Air Ministry 

approved the proposal based upon Watson–Watt’s record of success, 

authorizing £60,000, equal to $4 million in 2018, for five initial RDF 

stations along the coasts of Dover to protect the air approach to London.

Having suggested the original concept of radar only 10 months 

before, Watson–Watt’s team now had to construct a series of actual, 

working coastal early warning stations, entirely based upon the new 

“art” of RDF, and all in hopes that it could be done before it was too 

late. The race was on.

Notes

1. Swords, Technical History, 52.

2. Skolnik, Introduction to Radar, 9–10.

3. Burns, “Background to Development,” in Burns, ed., Radar Development, 23.

4. Swords, Technical History, 107.

5. Coulton, “Radar in the U.S. Army.”

6. Terrett, Emergency, 46.

7. Swords, Technical History, 115–6.

8. Terrett, Emergency, 123.
26 │ THE INVENTION OF RADAR 

9. Ibid., 48.

10. Ibid., 123.

11. Ibid., 127.

12. Ibid., 127–8.

13. Ibid., 129.

14. Thompson, Harris, Oakes, and Terrett, Test, 62.

15. Terrett, Emergency, 41.

16. Deighton, Fighter, 121.

17. Swords, Technical History, 82–4.

18. Watson–Watt, Pulse of Radar, 56–8.

19. Skolnik, Introduction to Radar, 11.

20. Strebeigh, “How England Hung the ‘Curtain’,” 125.

21. Carter, “Personal Reminiscence: RDF [radio direction finding] and IFF 

[identification-friend-or-foe],” 154.
THE INVENTION OF RADAR │ 27
Chapter 3

The RAF’s Fighter Control System

Air Ministry Experimental Set 1 at Bawdsey Manor

In May 1936, Watson–Watt’s radar team was moved from Orford 

Ness to Bawdsey Manor, near Felixstowe and 60 miles northeast of 

London, perched high atop the cliffs of England’s eastern coast, to 

supervise the building of the first operational radar station.1

 Assembling a team of brilliant young scientists from various British universities, they would continue to work and conduct training at the Manor 

until the start of World War II (fig. 3-1). In August, Henry Tizard called 

a conference at Biggin Hill, a Royal Air Force (RAF) airfield southeast 

of London, with three RAF officers and a civilian engineer.2

Figure 3-1. Bawdsey Manor on the English coast. (By permission from 

John Fielding, https://www.flickr.com/photos/john_fielding/14924955295.)

With Air Ministry approval, Tizard told this small group that a 

new secret capability now existed for detecting approaching bomber 

raids at ranges of 100 miles or more. Proposing that a fighter could be 

directed from the ground to intercept such raids, he tasked his team 
28 │ THE RAF’S FIGHTER CONTROL SYSTEM

to develop the procedures necessary to control such interceptions. As 

a beginning, he proposed the “Principle of Equal Angles” be used to 

establish interception geometry. The angle of fighter interception was 

calculated from an isosceles triangle consisting a baseline between 

the fighters and approaching enemy bombers (or enemy fighters, for 

that matter), and a second line formed from the bombers’ detected 

position and apparent heading to target. The third line of the triangle 

was the fighters’ line of interception from their position to a point of 

interception with the bombers. Ground controllers would calculate 

the angle between the baseline and the bombers’ heading to target. 

An “equal angle” or “Tizzy angle” would be the course or “vector” 

directed by the controllers to the fighters. The point at which the 

fighters’ vector line crossed the bombers’ heading line would be the 

predicted interception point.3

For the first few months, the four men attempted to develop manual 

rulers to help calculate the required interception angles. When nonmaneuvering interceptions became easy, the targets were ordered to “jink” 

or change their course of flight. Now the interceptions became complex, as the time delay between radar detection and position plot made 

it difficult to accurately determine the raid’s new heading and thus the 

three new angles involved. The fighters’ original course had to be altered in mid-flight, and the ground controller had to work fast.4

During one trial, as one of Tizard’s team members was controlling, 

the Biggin Hill station commander, Wing Commander Eustace Osborne Grenfell, saw that a mistake had been made in computing the 

fighter’s interception heading. There was no time to work out a new 

Tizzy angle. Estimating by eye, he voiced a snap correction—and the 

pilot made the interception! Impressed by his quick actions, Tizard reasoned an experienced fighter controller could do much of the controlling almost by instinct rather than through using formal calculations. 

The scope of Tizard’s experiments was thus widened, with more aircraft and more controllers. Over the next year, Tizard’s team would 

determine the best methods for controlling and would learn that the 

best controllers could manage up to four interceptions simultaneously.5

By September 1936, only one radar transmitter tower at Bawdsey 

Manor had been constructed. Due to shortages, work was going extremely slowly. The station’s first air exercise was to be conducted 

with the RAF that month—and it was a disaster, adding to the frustration. Watson–Watt was concerned; Tizard was furious. The work 

continued. Six months later, in March 1937, nearly a year and a half 
THE RAF’S FIGHTER CONTROL SYSTEM │ 29

after its approval, this first radar station, designated Air Ministry Experimental Set (AMES) 1, was handed over to the RAF for operational use. Flying as many as 10 bombers a day against AMES 1 

throughout the month of April, the RDF exercises were judged to be 

successful. Aircraft were routinely plotted out to 80 miles, and there 

was even one detection at 112 miles (fig. 3-2).6

Figure 3-2. Radio direction finding (RDF) operator plotting aircraft on 

the scope. (Reproduced from http://media.iwm.org.uk/iwm/mediaLib//39/

media-39665/large.jpg, Imperial War Museum [IWM] photo.)

The overall air defense structure, called “Chain Home,” was planned 

to have a transmitting station every 20 miles, no more than two miles 

from the eastern coastline, with every other station having a receiver, 

as well. Each transmitter used an enormous 350-foot steel tower 

(transmitting pulsed signals using one of four frequencies between 

22–30 megahertz, with a peak power of 200 kilowatts), while receivers 

used 240-foot wooden towers to minimize signal reflection. The system was able to detect the approaching raid’s altitude, and detection 

range was eventually 120 miles.7

 By July 1937, a second Chain Home 

station had been opened at Dover, and by August, a third station was 

operational at Essex. The first five RDF stations making up the new 

Chain Home system were declared operational (figs. 3-3 and 3-4).8
30 │ THE RAF’S FIGHTER CONTROL SYSTEM

Figure 3-3. Chain Home steel and wooden radar towers. (Reproduced 

from http://media.iwm.org.uk/iwm/mediaLib//36/media-36281/large.jpg, 

IWM photo.)

Figure 3-4. RDF station reporting aircraft to Fighter Command. (Reproduced from https://upload.wikimedia.org/wikipedia/commons/8/88

/Royal_Air_Force_Radar%2C_1939-145._CH15331.jpg, IWM photo.)
THE RAF’S FIGHTER CONTROL SYSTEM │ 31

The Control and Reporting System

As each RDF station was successfully built, the RAF next turned to 

devising a control and reporting (C&R) system to report the presence 

of enemy aircraft and to control the fighters sent up to intercept them. 

Overall tactical command of fighter assets was vested in HQ Fighter 

Command, at Bentley Priory in Stanmore, a north London suburb. 

The RAF commander-in-chief was now Air Chief Marshal Sir Hugh 

Dowding who had granted the original funds for AMES 1 back in 

1935. Later, the C&R system would also become known as the 

“Dowding System” (fig. 3-5).9

Figure 3-5. Air Marshal Sir Hugh Dowding. (Reproduced from https://

en.wikipedia.org/wiki/Hugh_Dowding#/media/File:Hugh_Dowding.)

In short order, the entire British Isles had been divided into four 

regions, each protected by an RAF fighter group. Each fighter group 

region was further subdivided into group sectors. Tactical control of 

fighters in each group area was delegated to fighter group headquarters. Once fighters were airborne, they were controlled directly by the 

appropriate group sector. Each sector headquarters, group headquarters, and the Fighter Command headquarters had an operations 

room in which all air activity within each respective area could be 

plotted and controlled.10
32 │ THE RAF’S FIGHTER CONTROL SYSTEM

As each RDF station reported aircraft positions simultaneously to 

Fighter Command, a means of resolving target duplications had to be 

found. “Filtering” was the name given to this process. An experimental filter room was set up at Bawdsey for the August 1937 Fighter 

Command exercise to sort out the plots passed by the three Chain 

Home stations. The filter room was then to “tell” the filtered plots to 

Fighter Command, and it later became installed as part of Fighter 

Command headquarters. Filtered plots could then be conveyed down 

to the subordinate group sector operations rooms for tactical fighter 

control once aircraft were airborne.11 Properly correlated target plots 

were then manually placed on general situation maps in the sector 

operations rooms by plotters wearing headsets and using “croupier’s 

rakes” to move the plots of friendly and hostile aircraft on the map. 

On a dais above each map sat the sector controller. At first, these officers were pilots who had flown in World War I (fig. 3-6). 

Figure 3-6. Operations room. (Reproduced from https://upload.wikimedia.org/wikipedia/commons/7/76/Radar_and_Electronic_Warfare_1939

-1945_CH13680.jpg, IWM photo.)
THE RAF’S FIGHTER CONTROL SYSTEM │ 33

As readiness or aircraft scramble commands were received at each 

sector, sent down by the group commander, they were posted for all 

to see. Readiness states ranged from “2 hour” where pilots were allowed to be anywhere on the field, to “1 hour,” to “30 minutes,” to “15 

minutes” as the imminence of each threat was assessed. “Come to 

readiness” was the call for pilots to run to their aircraft and be ready 

to take off within five minutes. 

Finally, “Scramble!” was the order to take off, usually made with a 

flare pistol. After a mission, squadrons were often “released” so they 

could stand down for maintenance and aircrew rest.12

When the group controller ordered a squadron to readiness, and 

the fighters scrambled, the sector controller would then speak to the 

flight leader using one of four radio-telephone (R/T) sets available to 

him. It was up to the sector controller to provide the flight leader 

what course and altitude to fly as well as the enemy’s current position, 

altitude, course, and number. Controllers used amplitude modulated 

(AM) radio transceivers having a range of 35-40 miles at 15,000 feet 

and were vulnerable to significant interference, including British 

Broadcasting Corporation (BBC) radio broadcasts. VHF radios were 

eventually introduced in late 1940, which had a better range of 100 

miles at 20,000 feet (fig. 3-7).13 Amazingly, almost all basic R/T code 

words used today for communications between controllers and pilots 

are the very same phrases invented by the RAF during this time.

A report reviewing the annual RDF exercise held during August 

1937 outlined the C&R system’s operation:

Information required by the three Groups will be obtained by at least 15 

[RDF] stations, the observers at which, in time of high raid density, will tell 

plots at a high rate. This information is to be filtered and passed accurately and 

speedily to Groups and Sectors simultaneously. This means that on the average, when stations are all bringing in raids, the Group teller will have to tell 

information receiver from five stations and will therefore have to tell information at five times the rate of the observers. . . . A Sector requires information 

accurately and speedily at the rate of one plot per minute per raid. If each 

Sector can handle even four simultaneous raids, plots must be received at the 

rate of four per minute.14

With four groups totaling 27 sectors, it is evident why one of the 

most acute problems for a sector controller was receiving timely plot 

data on which to base interception efforts. It also demonstrates why 

careful selection of RDF operators, plotters, and filterers was essential. 
34 │ THE RAF’S FIGHTER CONTROL SYSTEM

It should be noted that a significant proportion of the personnel employed at RDF stations and operations rooms were from the Women’s 

Auxiliary Air Force (WAAF). When three WAAF typists assigned to 

Bawdsey Manor had been trained to read and tell cathode ray “A-scope” 

radar returns, it became apparent that women adapted in many ways 

better than men to this tough and tiring work.15

Figure 3-7. The Dowding C&R system. (Reproduced from 1941 UK Air 

Ministry pamphlet, https://upload.wikimedia.org/wikipedia/commons/3/36

/Operations_Control_from_1941_pamphlet.jpg.)

Finally, after four furious years and the expenditure of £10 million 

(equal to almost $680 million today), the Chain Home network, consisting of 29 RDF stations, started a constant watch of the lengthy 

eastern English coast on Good Friday, April 1939 (fig. 3-8).16 As it was 
THE RAF’S FIGHTER CONTROL SYSTEM │ 35

clearly impossible to hide Chain Home stations with their massive 

350-foot steel towers, the Germans naturally became quite interested. 

Intrigued, the chief of the Luftwaffe signals service soon deployed the 

Graf Zeppelin, loaded with many high-frequency (HF) receivers—a 

flying radio laboratory. Launched at the end of May 1939, the airship 

crossed the English Channel and approached the coast of England.17

Figure 3-8. Chain Home coverage, 1939 and 1940. (Reproduced from 

https://upload.wikimedia.org/wikipedia/commons/d/de/Chain_home_

coverage.jpg.)

Detected by the Home Chain station at Canewdon, the biggest 

imaginable blip appeared on their A-scopes, moving slowly and majestically across the screen. The RAF, delighted to receive such a jumbo 

practice run at German taxpayers’ expense, followed the airship mile 

by mile as it slowly turned and began its northern run up the English 
36 │ THE RAF’S FIGHTER CONTROL SYSTEM

coastline. As the theater was quite foggy, the airship reported its estimated position along the coastline back to its headquarters in Frankfurt, Germany. The airship’s intercepted message caused much 

amusement at HQ Fighter Command, for the navigator’s reported 

dead reckoning was nine miles off his true course as tracked by Chain 

Home—he was flying over English territory itself!18

After completing its signals collection run, the airship continued 

north to Scotland, then turned east for home. All the crew received 

for their efforts, however, was only loud static. Since no voice transmissions were ever detected, the actual meaning of these huge “radio” 

towers continued to remain a total mystery to the Luftwaffe.19

When World War II commenced with the Nazi invasion of Poland 

in September 1939, the British C&R system (the most sophisticated 

in the world) was functioning smoothly. However, it would be the 

Battle of Britain that would put the system to the ultimate test.

The Battle of Britain

Flushed with confidence from the conquests of Austria, Czechoslovakia, Poland, Denmark, Norway, Holland, Belgium, Luxembourg, 

and finally France, Hitler’s war machine now turned its attention to 

Great Britain. The fate of the British Isles, if not World War II itself, 

now hung in the balance. In preparing for the invasion of Britain 

(codenamed Operation Sea Lion), Hitler first charged his commander-in-chief of the Luftwaffe, Reichsmarschall Hermann Goering, to establish air superiority over England and the English Channel.20 Said Goering in June 1940, “My Luftwaffe is invincible. So now 

we turn to England. How long will this one last—two, three weeks?”21

In June 1940, Prime Minister Winston Churchill expressed his 

grave forebodings of the impending battle:

The Battle of France is over. I expect that the Battle of Britain is about to begin. 

Upon this battle depends the future of Christian civilization. Upon it depends 

our own British life, and the long continuity of our institutions and our Empire. The whole fury and might of the enemy must very soon be turned on us. 

Hitler knows that he will have to break us in this island or lose the war. If we 

can stand up to him, all Europe may be free and the life of the world may move 

forward into broad, sunlit uplands. But if we fail, then the whole world, including the United States, including all that we have known and cared for, will 

sink into the abyss of a new Dark Age made more sinister, and perhaps more 

protracted, by the lights of perverted science. Let us therefore brace ourselves 
THE RAF’S FIGHTER CONTROL SYSTEM │ 37

to our duties, and so bear ourselves that, if the British Empire and its Commonwealth last for a thousand years, men will still say, “This was their finest hour.”22

Numbering only 2,300 pilots, the RAF was to protect England with 

approximately 600 Hawker Hurricane and Supermarine Spitfire 

fighters against nearly 1,000 Messerschmitt Bf 109 fighters protecting 

more than 1,400 Junkers Ju-88, Dornier Do 17, and Heinkel He 111 

bombers. Never before in the history of warfare had so few men held 

the fate of a nation in their hands. Moreover, never before was such a 

crucial battle to be fought entirely in the air (figs. 3-9, 3-10, and 3-11). 

Officially lasting from 10 July to 31 October 1940, the Battle of Britain can be described as having been fought in four phases.23

Figure 3-9. Battle of Britain bases. (Reproduced from Williamson Murray, 

Strategy for Defeat: The Luftwaffe, 1933–1945 [Maxwell AFB, AL: Air 

University Press, 1983], 49.)
38 │ THE RAF’S FIGHTER CONTROL SYSTEM

Figure 3-10. “Come to readiness!” (Reproduced from https://commons.

wikimedia.org/wiki/File:Pilot_seen_running_to_fighter.jpg, IWM photo.)

Figure 3-11. Supermarine Spitfire formation. (Reproduced from https://

commons.wikimedia.org/wiki/File:Supermarine_Spitfire_F_Mk_XIIs_

of_41_Sqn.jpg.)
THE RAF’S FIGHTER CONTROL SYSTEM │ 39

Phase One—Channel Warfare

Starting in July, the Battle began with German aerial attacks on 

British ships in the English Channel. RAF fighters, drawn in to protect the ships, were then shot down by the battle-tested Germans. In 

the first 10 days, 50 RAF fighters were destroyed by the superior 

Messerschmitts.24 The British sector controllers soon realized that if 

they answered the German attacks plane for plane, they would be 

bled dry. At this rate, the Fighter Command would cease to exist in 

just six weeks.25

Determined to sink every ship passing through the channel, the 

Germans continued to launch dive-bombers, day after day. Typical of 

one day’s efforts, a shipping convoy would fall under attack by more 

than 30 Junkers, protected by 50 Messerschmitts. However, the sector 

controller would launch only eight Spitfires into the air to engage the 

enemy to drive away the bombers. By the end of the day, of the original 20 ships in convoy, only four made it into port. RAF Air Marshal 

Dowding was pushed by the Admiralty to support the convoys with 

more fighters, but he refused. By August the British government decided it was easier to ship resources from western ports, then inland 

by rail, and so canceled all further Channel ship traffic. The restraint 

Dowding showed as he committed only a small handful of aircraft to 

engagements, and the reports brought back by Luftwaffe aircrews 

from their fighter engagements, encouraged the German high command to believe the RAF had few resources left. As he had originally 

bragged, Goering felt it would soon be over.26

Phase Two—Eagle Day

In August 1940 the Luftwaffe’s huge fleet of Heinkel bombers, escorted by Messerschmitt fighters, began attacking in full force against 

RAF fighter bases and several RDF stations near the coast to pulverize the British into surrender. Day after day, RAF Fighter Command 

responded with as many as 600 sorties against the attackers. However, being outnumbered four-to-one, the RAF fighters were being 

routinely shot down or forced away. Now the Battle of Britain entered 

its most intensive phase. Goering had named 13 August as Adlertag

or Eagle Day—the day on which the Luftwaffe’s massive air offensive 

would finally wipe out the RAF.27

However, the sector controllers were now learning the tricks employed by the Luftwaffe. When a fighter sweep of Messerschmitts 
40 │ THE RAF’S FIGHTER CONTROL SYSTEM

tried to draw the Spitfires away from their defensive positions, the 

controllers maintained their protective fighters patrolling closely 

over their airfields to engage any approaching bombers. By the end of 

Eagle Day, the Germans had mounted their greatest effort to date—

launching 1,485 sorties and losing 46 aircraft. The RAF had responded with 700 sorties but lost 13 fighters and 47 more destroyed 

on the ground.28 Both air forces were now locked in mortal combat.

Angered that his Eagle Day had not been triumphant, two days 

later, on 15 August, Goering launched his most intensive air assault 

during the Battle of Britain. Launching over 1,700 sorties (1,200 were 

fighter sorties) from bases in France all the way up to Norway, the 

Luftwaffe pounded targets and airfields all along England’s eastern 

coast.29 The RDF operators at the northern part of Chain Home, 

swamped with radar returns and lacking the experience of their 

southern colleagues, estimated the incoming raid size at about 30 aircraft. The sector controller scrambled his squadron. When the few 

fighters made visual contact, they found that the raid size was well 

over 100 “bandits”! Correctly concluding that this was the entire 

Luftwaffe’s effort in the north, the 13 Group controller vectored 

squadrons from every airfield in the group. The German bombers 

were decimated, and the Messerschmitts were caught off guard by the 

bold response.30

As an estimated 150 German bandits approached the English 

shore, the sector controller changed his orders. The German fighters 

were being plotted at 25,000 feet, and so Spitfires, far better suited to 

engage the Messerschmitts at high altitude than the slower climbing 

Hurricanes, were being scrambled. RAF command-and-control tactics allowed Fighter Command to preserve its fighter assets and ensured the entire fighter force was not on the ground refueling and 

rearming at the same time. A tremendous air battle ranged from 

Scotland to Devon, eventually resulting in the RAF losing 34 fighters 

in aerial combat—but the Luftwaffe’s losses totaled more than 75 aircraft. The Luftwaffe soon began to refer to 15 August as “Black Thursday.”31 Churchill famously said, after these two months of fighting:

The gratitude of every home in our island, in our Empire, and indeed throughout the world, except in the abodes of the guilty, goes out to the British airmen 

who, undaunted by odds, unwearied in their constant challenge and mortal 

danger, are turning the tide of the World War by their prowess and by their 

devotion. Never in the field of human conflict was so much owed by so many 

to so few.32
THE RAF’S FIGHTER CONTROL SYSTEM │ 41

Phase Three—The “Crucial Period”

The Germans were now changing their tactics and abandoned airfield and RDF station attacks and, on direct orders of Goering himself, switched to bombing aircraft production factories. Had the Luftwaffe continued to attack RAF airfields exclusively, the RAF might 

well have been grounded, and the Germans could have gained command of the air over southeastern England. No longer under direct 

attack, the RAF Groups gained critical time needed to repair their 

damaged airfields and RDF towers and to rest their exhausted pilots 

and ground crews. Nevertheless, the RAF had lost 25 percent of its 

pilots, who were replaced by flyers just arrived from training with less 

than two weeks’ squadron flying experience. Dowding wondered 

how he could keep English skies dangerous enough to delay a German invasion until wintertime with its tempestuous seas. At this rate, 

however, it seemed impossible.33

Phase Four—London Bombing

On 25 August a lone German bomber aircrew changed the course 

of the war. Slated to attack oil tanks at Thameshaven, the aircrew lost 

its way and dropped their bombs—in error—hitting London. Furious, Churchill immediately authorized a reprisal raid. That same 

night, 81 RAF bombers struck Berlin. Outraged, Hitler demanded 

massive retribution and began the German terror raids on central 

London.34 The controller of the southeastern group realized the Luftwaffe was now centering its attacks on London itself and scrambled 

greater numbers of fighters to confront them en route to London.35

The deadly Messerschmitt escorts could not reach London, and the 

Luftwaffe bombers were now attacked by swarms of RAF fighters. As 

a result, bomber formations were repeatedly broken up or deflected 

and thus forced to turn back for home. The great air battle of 15 September 1940 is now celebrated as “Battle of Britain Day.” The Germans 

sent 400 fighters to escort about 100 bombers part of the way to London, and Fighter Command ordered everything into the air. Nearly 

200 Spitfires and Hurricanes swarmed high above London, attacking 

the now unescorted bombers, and nearly 300 RAF fighter sorties were 

launched that day against German fighter escorts (fig. 3-12).

This massive concentration of fighters, larger than anything ever previously displayed by the RAF, convinced the Luftwaffe that Fighter Command was far from being the beaten force that German intelligence was 
42 │ THE RAF’S FIGHTER CONTROL SYSTEM

portraying. The sight of such a large fighter force—miraculously intercepting the Luftwaffe everywhere it turned—shattered German hopes.36

Figure 3-12. British and German dogfight vapor trails. (Reproduced from 

https://commons.wikimedia.org/wiki/File:British_and_German_

aircraft_a_dog_fight.jpg, IWM photo.)

Two days later, British intelligence intercepted a secret German radio message instruction for the dismantling of German airfields in 

Holland—Operation Sea Lion’s invasion of England was being postponed! For the Luftwaffe, it was just as well. Exhausted by the summer 

battles, the bomber units were depleted, and morale was low. Week after week, the RAF held its own against tremendous odds. Meanwhile, 

the Luftwaffe had become baffled, then frustrated, and finally completely disillusioned. How had RAF fighters known where and when to 

strike their bombers? Goering now turned his attentions to the techniques of nighttime bombing, and Hitler turned to maps of Russia.37

Just by fighting to remain intact, Fighter Command had won the 

Battle of Britain. It had won it thanks to the bravery of the RAF pilots, 

to the Spitfire and Hurricane fighters and those who maintained 

them, to Dowding’s unswerving leadership, and—most definitely—to 

the sector controllers and their secret RDF. The Germans believed 

British fighters were somehow being controlled by local radio stations, 
THE RAF’S FIGHTER CONTROL SYSTEM │ 43

and not by a vast, nationwide radar and radio command-and-control 

network. Luftwaffe signal interception units heard the process of RAF 

fighter squadrons being talked into battle. It was becoming evident, 

although not known how, that British officers somewhere near London 

somehow knew when German aircraft were airborne and from what 

direction they were attacking.38 Then there was the incomprehensible 

English phrase repeatedly being shouted by RAF flight leaders back to 

their controllers—“Tally Ho! Tally Ho!”39

Overall, Chain Home and the C&R system had allowed the outnumbered British fighters to turn up at the right time, even while 

outnumbered, to intercept Luftwaffe raids time after time after time. 

Said Gen Adolf Galland, one of the great German fighter aces of the 

war, who would eventually command the fighter defenses of the 

Third Reich, “From the very beginning the British had an extraordinary advantage which we could never overcome throughout the 

war—radar and fighter control. For us and for our command this was 

a surprise, and a very bitter one. The British fighter was guided all the 

way from takeoff to his correct position for an attack on the German 

formations. We had nothing of the kind.”40

The Introduction of Ground-Controlled Interception

With their success in radar development, British radar engineers 

in August 1940 replaced several of the huge 350-foot fixed antennas 

of the Chain Home network with a new, smaller, rotating antenna 

that was used for transmitting and receiving radar pulses—a technological marvel. They also unveiled a new type of radar scope to replace the A-scope, called a plan position indicator (PPI). The term 

“plan position” described the scope’s view as being planar, or a “bird’s 

eye view” from above, rather than the standard side-view presentation then in use by radar operators.

The PPI was a round cathode ray tube that had a rotating beam of 

light called a “sweep,” turning like a clock’s second hand around the 

center of the tube in exact synchronization with the turning of the radar antenna as it transmitted. Radar echoes collected by the same 

turned antenna appeared as points of light called “blips” along the 

sweep as it rotated. A coating on the scope provided a phosphorescent 

afterglow so that a target’s reflection remained visible until renewed by 

the next sweep. What we now traditionally picture as being the typical 
44 │ THE RAF’S FIGHTER CONTROL SYSTEM

radar screen, it was, in fact, an astounding breakthrough. Moreover, it 

paved the way for a new form of more closely controlling aircraft—

ground-controlled interception (GCI) (fig. 3-13).41

Figure 3-13. Rotating GCI radar. (Reproduced from https://en.wikipedia.

org/wiki/Dowding_system#/media/File:GCI_(Ground_Control_of_Interception)_radar_installation_at_RAF_Sopley,_Hampshire,_1945._CH

15188.jpg, IWM photo.)

Obviously, for controlling fighters to intercept enemy aircraft, particularly during night interceptions, GCI with its marvelous PPI far 

surpassed the cumbersome filtering of returns and the time-consuming 

plotting on situation maps. For the first time, a GCI controller could 

actually “see” the aircraft as they flew across the countryside, rather 

than watching voiced plots being pushed across a map. By studying 

the PPI, the GCI controller could determine the positions of the 

fighters, identified by the newly invented identification-friend-or-foe 

(IFF) technology, the RAF’s Mark I IFF system, and those of the enemy, 

not displaying a friendly IFF signal. The GCI controller could then provide timely R/T code word instructions directly to the fighter to successfully conduct the interception. The ingenious GCI transformed the 

British radar system from one providing a basic early warning capability into an actual means for dependable air interception control. 
THE RAF’S FIGHTER CONTROL SYSTEM │ 45

Clearly, the invention of GCI was as significant as the invention of 

pulse radar detection itself (fig. 3-14).

Figure 3-14. GCI controller and plotters. (Reproduced from http://www.

raf.mod.uk/news/archive.cfm?storyid=E46A70BC-5056-A318-A867D971EE41E2CA, RAF photo.)

The first GCI sets were built at the Telecommunications Research 

Establishment at Worth Matravers, on England’s southern coast in 

spring 1940, too late for use during the Battle of Britain, and began its 

series of operational tests. Wrote one research engineer:

During that lovely summer, we often saw hostile day bombers passing over us. 

One day we counted seventy-two of them . . . . After our day’s work, many of 

us went to our GCI station, hoping that this would be the night on which civilian scientists working as controllers at a research station would be the means 

of bringing down a night bomber . . . it is sad to record that [they] . . . failed to 

obtain a kill. They were replaced by RAF controllers who, in fact, did the job 

much better.42

The first RAF GCI sets were called Chain Home–Low (CHL), as 

they provided low-altitude air coverage along the British coastline. 

The first operational CHL/GCI set went on watch on 18 October 

1940. Six sets replaced RDF stations by Christmas, and a total of 12 

were on duty by January 1941.43 These first CHL/GCI stations were 
46 │ THE RAF’S FIGHTER CONTROL SYSTEM

either fixed or transportable, requiring eight vehicles, operated at 

about 209 MHz, had a peak power of around 100 kW, and had a detection range of over 90 miles.44

GCI was proving itself to be especially critical in assisting RAF 

fighters to attack German nighttime bombing raids on London, 

which were now becoming the norm, as radar was the only certain 

means to detect and intercept bombers in the dark. Serious night 

bombing of London had begun in September 1940, and until midNovember, except for one night of bad weather, an average of 160 German bombers attacked the city every 24 hours. This was the “Blitz.”45

Throughout the Battle of Britain, visiting American Army Signal 

Corps and Air Corps officers watched the RAF’s radar air defense 

system with keen interest, especially the new and fantastic GCI. As 

they watched over the shoulders of their soon-to-be wartime allies, 

these officers were busily taking notes and analyzing what steps 

would be needed to help the US Army’s Aircraft Warning Service 

begin to take shape. For unlike the RAF, by 1940 the Army had only 

a few research radar sets, no GCI, no radar network, and no controllers. There was much to be done.

Notes

1. Watson–Watt, Pulse of Radar, 114.

2. Wood and Dempster. Narrow Margin, 79.

3. Ibid.

4. Ibid.

5. Millar, Bruneval Raid, 27.

6. Watson–Watt, Pulse of Radar, 115.

7. Bickers, Battle of Britain, 30.

8. Gough, Watching the Skies: The History of Ground Radar in the Air Defense of 

the United Kingdom, (Her Majesty’s Stationery Office, 1993), 6.

9. Ibid., 4.

10. Bickers, Battle of Britain, 31.

11. Deighton, Fighter, 114.

12. Ramsay, Battle of Britain Then and Now, 14–28.

13. Bickers, Battle of Britain, 35.

14. Ibid, 33–4.

15. Bungay, Most Dangerous Enemy, 49.

16. Swords, Technical History, 195.

17. Brown, Radar History of World War II, 97–8.

18. Ibid.

19. Millar, Bruneval Raid, 36–7.

20. Deighton, Fighter, 31.
THE RAF’S FIGHTER CONTROL SYSTEM │ 47

21. Moll, “Battle of Britain,” 45.

22. Ibid, 42.

23. Deighton, Fighter, 140.

24. Moll, “Battle of Britain,” 47.

25. Deighton, Fighter, 164.

26. Ibid., 176, 179.

27. Ibid., 173, 196.

28. Ibid., 199–200.

29. Ibid, 207.

30. Ibid, 205.

31. Ibid, 211.

32. Moll, “Battle of Britain,” 52.

33. Deighton, Fighter, 250–2.

34. Ibid. 252.

35. Ibid. 226–7.

36. Ibid. 262.

37. Ibid., 262–3.

38. Ibid. 187.

39. Millar, Bruneval Raid, 45–6.

40. Moll, “Battle of Britain,” 45, 50.

41. Putley, “Ground Control Interception,” 162–3.

42. Millar, Bruneval Raid, 93.

43. Swords, Technical History, 239.

44. Watson–Watt, Pulse of Radar, 218.

45. Millar, Bruneval Raid, 68.

Chapter 4

The American Aircraft Warning

Service Takes Shape

The Army Air Defense Command

As previously mentioned, in 1933 the US Army had undertaken a 

major reorganization to better carry out its territorial defense responsibilities. Four major continental defense field armies (First United 

States Army, Second United States Army, Third United States Army, 

and Fourth United States Army) were established with specific geographical areas of responsibility. Within each of these four field armies 

there also existed an air district responsible for controlling the field 

army’s limited air assets operated by Air Corps personnel.1

 Later, in 

1935, the War Department issued its general directive on air defense 

to the four field army commanders designed to prepare an integrated 

air defense consisting of field-army-controlled pursuit aviation, AAA, 

and aircraft warning services for defending against coastal air attacks.2

During summer 1939, with the Signal Corps’s breakthroughs in 

developing the SCR-268 short-range and SCR-270 long-range radars, 

the Army announced that new secret electronic “detectors” would 

soon replace sound locater equipment for air defense. Further, the 

Signal Corps was ordered to begin researching possible detector sites 

and information center locations that would be required in the future.3

 The future arrived that fall. In September 1939, Germany invaded Poland, and Europe was plunged into war. Shocked by this act 

of aggression, the United States was now confronted with having to 

seriously reconsider its self-defense needs.

Gen Hap Arnold, now chief of the Air Corps (fig. 4-1), was particularly worried about the lack of an organized continental air defense and urged that a study be conducted to review this problem. 

The study, completed in early 1940, recommended that 23 long-range 

detector sites be positioned around the United States, providing air 

defense information to nine centralized information centers.4

 Without an air defense system to protect its thousands of miles of coastline, 

the Army had a very long way to go.
50 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

Figure 4-1. Gen Hap Arnold. (Reproduced from https://upload.wikimedia.

org/wikipedia/commons/3/37/021002-O-9999G-013.jpg, US Army photo.)

The security of the strategic Panama Canal was of immediate concern to the War Department. On 1 January 1940, the Signal Company, Aircraft Warning, Panama, was established and ordered to prepare for deployment to the Canal Zone (CZ). Consisting of 93 men 

pulled from numerous Signal Corps units, this first-of-its-kind company went into emergency training at Fort Monmouth. Using the 

SCL’s fixed SCR-271 research radar set, they practiced “the strange 

and uncertain business of electronic detection.” It was uncertain that 

they would have their own radar set by the time they arrived in Panama later that year.5

Having just witnessed the successful SCR-270 tests at Fort Hancock, CZ, in December 1939 and with the results of General Arnold’s 

air defense study, Secretary of War Woodring announced that a new 

command would soon be established in the Northeastern United 

States to provide warning and air defense against attacks. Two months 

later, in February 1940, the War Department officially announced the 

establishment of the experimental Air Defense Command (ADC) at 

Mitchel Field, on Long Island, New York, under the command of Air 
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 51

Corps Brig Gen James Chaney (fig. 4-2).6 The ADC, operating in the 

northeast United States under the direction of the First Army commander, was to serve as a model for a nationwide air defense command system. This air reorganization was only partially carried 

through in 1940; the air districts were not activated until 15 January 

1941, and the expansion of the air defense command system was not 

approved until March1941. Staffed with only 10 officers, ADC would 

be responsible for coordinating the three components of air defense—

AAA guns and searchlights, Air Corps pursuit planes, and Signal 

Corps detection and communication equipment—into a functional 

AWS structure to support First Army.7

Figure 4-2. Maj Gen James Chaney. (Reprinted from Kenneth Schaffel, 

The Emerging Shield: The Air Force and the Evolution of Continental Air 

Defense, 1945–1960 [Washington, DC: Office of Air Force History, 

1991], 25, http://media.defense.gov/2010/May/26/2001330263/-1/-1/0/

AFD-100526-024.pdf.)

ADC was viewed as primarily a planning organization, charged with 

developing a system of unified air defenses for cities, vital industrial 

areas, and continental bases within First Army’s area of responsibility. 
52 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

It would also cooperate closely with the British RAF during its upcoming Battle of Britain, observing radar and fighter control employment in actual combat.8

 ADC asked the War Department in February 

1940 for permission to recruit an initial cadre for AWS duty and 

promised they would be trained and ready for the July 1940 maneuvers, quite a promise since there were still very few SCR-268 radars in 

service. They had just started to arrive from SCL during the past year. 

Only one SCR-270 existed (still at Fort Hancock completing final 

Army service testing), plus one fixed SCR-271, the SCL’s research set 

still undergoing development and being shared with the recently 

formed Panama AWS troops for their hasty training.9

Amazingly, the War Department granted the recruiting request, 

and on 1 March 1940, the 1st Signal Aircraft Warning Company 

(SAWC) was activated. It would be the first of over a hundred Army 

SAWCs that would be formed during World War II. The company’s 

initial troop strength consisted of 30 signalmen from Fort Monmouth, 10 men from other units, and 43 new recruits—all of whom 

would soon report to Fort Monmouth to begin necessary training on 

the soon-to-be certified SCR-270 set.10 The building of AW units was 

now officially underway. During spring 1940, as Hitler’s blitzkrieg 

stormed across Europe, the War Department ordered the First Army 

to establish a formal AWS network along the eastern seaboard. The 

Third Army was to develop an AWS from the Carolinas to the Gulf of 

Mexico; and the Fourth Army, cooperating with Second Army, was to 

establish its AWS along the entire Pacific coastline.11

Army officers visiting England were also to observe the British air 

defense system, and they were now returning with enthusiastic reports about the RAF’s successful radar network. Consequently, in May 

1940 the War Department ordered the commanders of the four field 

armies to immediately begin incorporating the newly developed radar 

sets, codenamed “radio-B” detectors, into their AWS networks.12 To 

support this monumental tasking, the ADC and the Signal Corps 

now began drafting the first plans to provide for the air defense of the 

United States. They planned on using 31 mobile detectors ringing the 

four continental air districts, which would require a staggering total 

of 3,786 AW signal troops.13

In August 1940, ADC was ordered to participate in First Army 

maneuvers in New York, one of the purposes being “to develop a system of unified air defense for the protection of armies in the field.”14

Again, the telephone company was pressed into service, connecting 
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 53

360 observation posts and 46 fire lookout stations to an information 

center at Watertown, New York (fig. 4-3). Using over 4,600 civilian 

observers, it was the largest exercise of an AWS held to that date. The 

final report stated, “Methods employed in the organization and operation of the Aircraft Warning Service, with revisions indicated by 

present experience in the maneuvers, are considered very satisfactory 

as a guide to future operations.”15

Figure 4-3. Air defense exercise at Watertown, New York, 1940. (Reproduced from Schaffel, The Emerging Shield, 28.)

Participating in the First Army maneuvers gave ADC its first valuable experience in preparing and testing air defense methods. Now it 

could begin preparing detailed plans for various coastal sectors, using personnel and facilities of the US Forest Service, railroads, electric utility companies, and other organizations. By December 1940, 

rudimentary air defense information centers had been built in several 

major cities on both the Atlantic and Pacific coasts. Word was now 

circulating, however, that the War Department was planning to transfer the entire air defense mission to the Air Corps.16

In January 1941, ADC undertook a huge “Test Sector” exercise involving most of Massachusetts, Connecticut, Rhode Island, and Long 

Island, New York. Boundaries were specifically chosen to test coordination problems between the Boston and New York information centers (fig. 4-4). Each information and filter center was organized differently to test the relative efficiencies of skilled women telephone 
54 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

operators, untrained civilian volunteers, and skilled military personnel. Some 700 observation posts were manned by more than 10,000 

civilian observers. No doubt influenced by the RAF’s successful system, 

filtered information was transmitted to plotters where it was displayed 

for the benefit of the controllers in making their tactical decisions.

Figure 4-4. Air defense exercise at New York City, 1941. (Reproduced 

from Schaffel, The Emerging Shield, 31.)

ADC was disappointed with the performance of the ground observers. They had used only instruments provided by mail, and the 

quality of observations varied widely. The experimental use of women 

in the centers had gone well, however. Overall, ADC recommended 

that critical AWS military personnel should only be required as instructors or supervisors and concluded that civilians could perform 

most of the duties carried out at each center.

In March 1941 the rumor that air defense would be transferred to 

the Air Corps became fact, and by June ADC ceased to exist. In the 

single year of its existence, however, ADC had generated a revolution 

in air defense thought. Pursuit aircraft were now viewed as the principle defense against aerial attack, and an effective AWS was seen as 

the key to successful interception. As ADC expressed it:
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 55

The Aircraft Warning Service does not merely “alert” defending pursuit aviation; it furnishes pursuit with the detailed, timely, and continuous intelligence 

necessary for pursuit interception. A proper conception of an Aircraft Warning Service is that of a complex and highly organized service carefully adjusting to the tactical requirements of the agencies it serves and efficiently integrating into the defense of a strategic area.17

Overseas Air Defense Planning

The fall of France to the German war machine in June 1940 meant 

time was now of the essence. Congress was now considering a national mobilization, which would result in expanding the US Army to 

375,000 personnel. As a result, a Signal Corps board was held in 

Washington, DC, that month to determine how many AW troops it 

would require as part of this build-up. Out of this board came a plan 

that the National Guard would be especially suitable for aircraft 

warning duty and they could study the SCR-270 in their local armories. The board urged that SAWCs be organized in every coastal state 

where detector stations were being planned. It was envisaged that 

Guardsmen could join in the air defense of their section of the country, defending their hometowns in much the same tradition of Lexington and Concord.18

However, despite the modest successes achieved by the ADC, it 

was clearly apparent that the Army was unprepared to conduct any 

major continental air defense operations and was now under enormous pressure to develop serious air defense plans for the nation. 

Overseas, it was the same story. At the beginning of 1940, the Army 

chief of staff, Gen George C. Marshall, cautioned: “As long as the British Fleet remains undefeated and England holds out, the Western 

Hemisphere is in little danger of direct attack.” However, he added, 

“the situation would become radically changed” if the British Fleet 

were to be sunk or to surrender.19 Therefore, plans had to be drawn 

up immediately to meet this possibility as well.

Defending American interests in the Western Hemisphere were 

the Army’s small overseas garrisons, which were organized into four 

major departments: the Panama Canal and Puerto Rico departments 

in the Caribbean, the Hawaiian Department in the Pacific, and the 

Philippines Department in the Far East.20 With the war now consuming Europe, the Signal Corps worried whether its various overseas 
56 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

AWS efforts in each of these departments would be enough, or even 

in time.

Having completed their brief training at Fort Monmouth, the 

unique Signal Company, Aircraft Warning, Panama, left for the CZ in 

May 1940. Their mission had such high priority they wound up taking the SCL’s research SCR-271 with them. They were to guard the 

Canal’s Caribbean approaches from Fort Sherman and the second 

station on Taboga Island on the Pacific side. The Fort Sherman site 

became the Army’s first operational radar station (fig. 4-5).21

Figure 4-5. SCR-271 radar station in Panama. (Reproduced from Dulany 

Terrett, US Army in World War II: The Technical Services: The Signal 

Corps: The Emergency [Washington, DC: Office of the Chief of Military 

History, 1956], 285.)

In August 1940, Winston Churchill offered British territories for 

US defense garrisons, in trade for old US Navy destroyers, which the 

Royal Navy desperately needed. Consequently, plans were soon 

drafted by the Air Corps for deploying small air defense fighter forces 

to the islands of Bermuda, the Bahamas, Jamaica, and Trinidad to 
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 57

protect strategic air and sea lanes in the Caribbean. Included in these 

plans were AWS frontier companies at each location.22 To protect the 

Atlantic sea lines of communication between the United States and 

Europe, planning now began to move air defense aircraft and AW 

units to Newfoundland (Canada), Greenland, and Iceland to check 

possible German North Atlantic troop movements or ship assaults.23

Plans were started during 1940 to activate and deploy AW units and 

pursuit aircraft to Alaska, while additional AW units were to augment 

the existing pursuit squadrons currently in the Philippines and Hawaii. 

Unfortunately, while plans were being made to send troops and materiel to these locations, no radar sets were yet available to deploy with 

them—nor would there be for yet another 18 months, until fall 1941.24

The need for AW companies became relentless, and it was quickly 

apparent that the planned requirement for new AW units would soon 

exceed the available number of currently trained AW personnel. In 

May 1941, a newly formed Air Defense board, consisting of senior 

ranking Air Corps, Signal Corps, and Coast Artillery Corps (CAC) 

officers, held its first meeting in Washington, DC, to survey the Army’s AW planning and to propose possible solutions. The board determined the Air Corps should be strengthened by 1,238 officers and 

7,796 enlisted men to implement its share of the air defense system.25

In September 1941, the Air Defense Board recommended the Signal 

Corps increase its AW personnel by an additional 2,200 officers and 

40,200 enlisted men. For the Signal Corps alone, this tripled the 

number of men currently on AW duty at the time. Of this new recommended total, the War Department approved 900 officers and 17,000 

enlisted men to begin training by that December.26

This increase still did not prove enough. Another board, held by the 

War Department in November 1941, concluded the “organization, activation, training and equipment of AWS units had not kept pace with 

the expansion of pursuit units.” While there were 13 aircraft pursuit 

groups at the time, only five AW companies had officially been 

formed—no AW battalions existed, let alone AW regiments. The board 

stated, “the present situation places the provision of pursuit Aircraft 

Warning Service teams at the earliest date in priority, far above the 

foreseeable demands for any units in the United States Army.”27

The effort to build a pool of trained personnel for AWS duty since 

fall 1940 had produced approximately 2,900 trained AW enlisted men. 

However, now, with plans being drawn up to quickly deploy AW units 

overseas to task forces in Panama, the Caribbean, the North Atlantic, 
58 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

Alaska, Hawaii, and the Philippines, the board recommended a second AWS recruiting effort of an additional 986 officers and 17,106 

enlisted men to begin in December 1941.28

Signal Corps Aircraft Warning Training

Technical training was a major mission of the Signal Corps—and 

now the urgency of national mobilization demanded that it cut that 

technical training time drastically (fig. 4-6). While the Fort Monmouth’s Signal Corps School normally required 10 full months for 

training enlisted troops, the Army had too few officers to allow them 

to attend such lengthy special schooling during the growing crisis. 

Therefore, National Guard and Reserve Signal Corps officer training 

was reduced at the school from nine months to only three months. 

Graduates were soon ridiculed as “ninety-day wonders.” Assuming 

West Point graduates were capable of even quicker study, the regular 

officer’s course was cut to just a single month overview of wire, radio, 

photography, and the newly emerging aircraft warning service. All 

enlisted technical training was shortened to just three months or less. 

There was no other way—the growing emergency demanded it.29

Figure 4-6. Signal Corps field training class. (Reproduced from Terrett, 

The Emergency, 75.)
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 59

Later in summer 1940, the United States began its long road to 

national rearmament. While the Battle of Britain was being fiercely 

waged in Europe, all four US Army field armies began massive efforts 

to improve their readiness, including practicing air defense methods 

in earnest for the first time. The Third Army conducted its largest 

peacetime ground maneuvers to that date in Louisiana, but it had to 

improvise its AWS company. Meanwhile, during field maneuvers in 

the Northwest, the Second Army complained to the War Department 

that it had no aircraft or AWS at all with which to train. Overall, 

training went agonizingly slow due to the lack of both materiel and 

workforce. With great frustration, one general reported that he hoped 

“to have a defense force in the next two or three years.”30

That fall, unable to resist the fears of being unprepared any longer, 

Congress passed the Selective Service Act of 1940, authorizing conscription and an Army of 1.4 million personnel—a ten-fold increase 

in size. The United States was now officially mobilizing for war. By 

October 1940, the draft was in full swing, and new inductees began 

pouring by the thousands into Army and Navy induction centers 

across the country. 31 The Signal Corps responded to this challenge by 

establishing, over the course of 18 months, three major electronic 

training centers related to radar or AWS operations:

• The Eastern Signal Corps Training Center (at Fort Monmouth, 

New Jersey) was home of the existing Signal Corps School, as well 

as the Signal Corps’s own Officer Candidate School, and was responsible for most Army radio and telephone training throughout the war.

• Later, in February 1942, the Midwestern Signal Corps Training 

Center (at Camp Crowder, near Neosho, Missouri) would become the Signal Corps’s largest replacement training center. It 

would offer many of the basic signalman training courses, as 

well as specific AWS classes.32

• Finally, in June 1942, the Southern Signal Corps School, located 

at Camp Murphy, on Hobe Sound near Riviera, Florida, would 

begin teaching trainees how to repair the new and intricate SCR268 and SCR-270 series radar sets.33

For every newly arriving recruit, the first days at Camp Crowder 

were spent in a succession of queues for filling out forms, assembling 

a uniform, getting a haircut, shots, and more forms. These first three 
60 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

weeks of basic training were spent learning how to march, wear a 

uniform, salute, do push-ups, pitch a tent, put on a gas mask, and fire 

a pistol.34

Only after successfully learning how to be a soldier did these recruits begin their AW technical training. For many, it was on to Fort 

Monmouth’s Signal Corps School, the Army’s primary electronics 

training school, for advanced signalman training. Fort Monmouth 

was soon flooded with trainees arriving at a rate of 7,000 students per 

quarter. By January 1941, the commandant of the school was forced 

to lease 10 extra acres to pitch winterized tents to hold the overflowing population. In time, the school would conduct basic signalman 

classes to over 5,000 trainees at once (figs. 4-7, 4-8, and 4-9).35

In March 1941, responding to concerns about the lack of specific 

AW technical training, the school began developing several new 

courses required for the still-experimental AW companies being 

planned. It recommended that radar maintenance training be conducted to no more than 100 students at a time, as no one knew very 

much about the still highly classified radio-B equipment (fig. 4-10). 

As a beginning cadre, five noncommissioned officers were chosen to 

become the department’s first radar instructors. They were first put 

through a short course in radar maintenance, followed by a brief 

course in radar operations—that was enough for a start.36

Figure 4-7. Arriving at Fort Monmouth for training. (Reproduced from 

Terrett, The Emergency, 75.)
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 61

Figure 4-8. Marching to class at Fort Monmouth. (Reproduced from 

Thompson, Harris, Oakes, and Terrett, The Test, 202.)

Figure 4-9. Fort Monmouth electronics training. (Reproduced from 

Terrett, The Emergency, 213.)
62 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

Figure 4-10. SCR-270 mobile radar. (Reproduced from photo by 1st Lt 

Harold Zahl, https://commons.wikimedia.org/wiki/File:SCR-270-set-up.jpg,)

Thus, in June 1941, the school’s new Aircraft Warning Department 

officially opened at Fort Monmouth, with the first radar equipment 

class consisting of 10 officers and 40 enlisted men. Training lasted 

four months and borrowed from Fort Hancock the first mobile SCR270 radar certified for Army use. Within a year, the capacity of the 

AW Department would swell to over 400 students.37 The AW Department would soon institute a nine-week AW plotters course and a 13-

week AW operations course, as well.38

However, the AWS radar maintenance requirement eventually 

grew so large it finally exceeded the AW Department’s capacity. At 

the same time, a proposal to create a new, joint Signal Corps–Coast 

Artillery Corps–Air Corps training school had been under consideration. In October 1941, Secretary of War Stimpson approved this creative idea, and the Signal Corps’s new Camp Murphy radar school 

was soon under construction.39

Located on 11,500 acres of inaccessible swampland near West 

Palm Beach, Florida, it was the perfect location to discourage unwanted observations of secret radar training. The new school devoted 
THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE │ 63

two months to the study of electronics principles and one month to 

radar, UF, and microwave principles. Graduates then went on to aircraft warning or antiaircraft units where radar played a predominant 

role or to Signal Corps depots to manage the acquisition, supply, and 

repair of the Army’s newly arriving radar sets.40 Classes began at 

Camp Murphy in June 1942. However, like the rest of the Army, the 

school immediately lacked enough radar sets for training, having 

only six SCR-268s for the Gun Laying Division and two SCR-270s for 

the Reporting Division courses.41 Overall, radar students had to be 

highly motivated and have considerable initiative to learn and master 

the difficult topics of radar theory and equipment maintenance. As 

such, these radar repairmen were considered the elite—the “Phi Beta 

Kappa” of the Signal Corps.

Notes

1. Conn, Engelman, and Fairchild, Guarding the United States, 119.

2. Ibid., 54.

3. Terrett, Emergency, 136.

4. Conn, Engelman, and Fairchild, Guarding the United States, 62.

5. Terrett, Emergency, 149.

6. Ravenstein, Organization and Lineage, 12.

7. Conn, Engelman, and Fairchild, Guarding the United States, 24.

8. Williams and Fellow, “Deployment of Army Air Forces,” 152–3.

9. Terrett, Emergency, 150–1.

10. Ibid.

11. Fourth Air Force. Defense Plans and Operations, 75–6.

12. Williams and Fellow, “Deployment of Army Air Forces,” 153.

13. Terrett, Emergency, 151.

14. History, Air Defense Command, chapter 1 and 101–9.

15. Ibid., 259 and Appendix XI.

16. Fourth Air Force. Defense Plans and Operations, 75–6.

17. History, Air Defense Command, chapter 1 and 117.

18. Terrett, Emergency, 161.

19. Conn, Engelman, and Fairchild, Guarding the United States, 9.

20. Ibid., 392.

21. Terrett, Emergency, 151.

22. Conn, Engelman, and Fairchild, Guarding the United States, 364.

23. Ibid., 358.

24. Terrett, Emergency, 151.

25. Ibid., 287.

26. Thompson, Harris, Oakes, and Terrett, Test, 24.

27. History, III Fighter Command, vol. 2, 91–2.

28. Ibid., 93.
64 │ THE AMERICAN AIRCRAFT WARNING SERVICE TAKES SHAPE

29. Terrett, Emergency, 210.

30. Ibid., 151.

31. Ibid., 203–4.

32. Thompson, Harris, Oakes, and Terrett, Test, 189–97. 

33. Ibid., 212.

34. Terrett, Emergency, 215; and Thompson, Harris, Oakes, and Terrett, Test, 190.

35. Terrett, Emergency, 212–3.

36. Ibid., 218–9.

37. Ibid., 219.

38. Thompson, Harris, Oakes, and Terrett, Test, 53.

39. Ibid., 54.

40. Ibid., 288.

41. Ibid., 213.
Chapter 5

The Army Air Forces Take Charge

First Radars Arrive

In August 1940, Congressional funding totaling $1 million ($17 

million in 2018 dollars) was secretly appropriated to fund a contract 

to build SCR-268s. It was an unheard of sum for a government investment in a single item, and industry was unprepared to deal with it. 

The Western Electric Corporation took up the challenge, protected 

from the risk by its cushion of existing laboratories and massive research capital.1

However, to most airmen, the American radar set was not worth 

the effort. As early as October 1940, a Signal Corps representative in 

London recommended the United States immediately purchase RAF 

radar, radio, and other equipment directly from the British government, saying that “beyond a doubt, the British detectors are much 

farther advanced than those we are developing in the United States.” 

General Arnold recommended in November 1940 not only that copies of the RAF radar be reproduced but also that production of what 

he felt was the less-capable SCR-268 should be stopped.2

 Even though 

the RAF’s Chain Home radar had less range and wasn’t mobile, the 

Air Corps still viewed it as being more desirable. Moreover, the overall effectiveness of the RAF C&R network gave the false impression 

the American equipment was inadequate, rather than the inadequacy 

of the Army’s untrained or inexperienced radar operators.

During summer 1940, the commander of the Air Defense Command, General Chaney, visited England to observe firsthand the RAF 

radar defenses that were proving themselves so successful during the 

Battle of Britain. Chaney’s secret report to the War Department described the British AWS structure, the types of radar equipment they 

were using, and their aircraft controlling procedures. The report was 

later distributed to the four field armies air districts to study and use 

in AWS planning.3

 Having seen the fantastic capabilities of the new 

GCI radar, General Chaney demanded that US radars be made 

equally as capable as those of the British, that building US radar capabilities was among his highest priorities, and that the Army take “immediate action.”4

 Air Corps observers were also dazzled by GCI and 
66 │ THE ARMY AIR FORCES TAKE CHARGE

requested the SCR-268 be improved to a 70-mile range, a three-mile 

azimuth accuracy, and an elevation sensitivity within 1,000 feet (see fig. 

5-1). In General Arnold’s view, the Signal Corps was the supplier to the 

Air Corps, this was what the Air Corps urgently needed, and so it was 

up to the Signal Corps to get it—and get it fast! It was simple as that.5

Figure 5-1. SCR-268 mobile radar. (Reproduced from Terrett, The Emergency, 126.)

Pressured by the Air Corps, the Signal Corps began special efforts 

to increase the range of the SCR-268. These efforts resulted in the 

development of a new set designated “SCR-516” and gave the SCR270 a new height-finding capability.6

 The Signal Corps was also able 

to obtain from the Army $2,646,000 ($47 million in 2018 dollars) to 

directly procure British equipment for testing.7

 However, the British 

government hesitated to immediately provide the requested equipment, frustrating the Signal Corps’s research and development efforts, as well as fueling Air Corps criticism.8

 Try as they might, and 

under intense pressure, the Fort Monmouth radar engineers were 

never able to turn their SCR-268 and SCR-270 sets into what they 

were not—British GCI radars.

In February 1941 the tide slowly began to turn. Almost four years 

after its first secret demonstration back in 1937, the first factory-built 

SCR-268 radar sets began arriving from Western Electric factories. 

These sets were immediately sent to support the growing number of 

AWS units now deploying overseas. A total of 491 radar sets would be 
THE ARMY AIR FORCES TAKE CHARGE │ 67

delivered by Western Electric during 1941.9 Eventually, nearly 2,000 

SCR-268 radars would be built and deployed until they were declared 

obsolete in January 1944.10 However, frustrated that air defense was 

going “nowhere fast,” and believing the new SCR-268s were going to 

Army antiaircraft units exclusively, General Arnold requested (and 

received) 20 new SCR-268s for Air Corps use instead of the promised 

SCR-270 long-range early warning radars.11 The new Western Electric sets were also solving the Signal Corps School’s growing training 

problems. By the middle of 1941, having received two new commercial SCR-268 sets plus two custom-built SCR-270 sets delivered directly from the Signal Corps Lab, the Aircraft Warning Department 

was now finally able to increase its radar maintenance training course 

from 100 to over 400 students at one time (fig. 5-2).12

Figure 5-2. SCR-270 mobile radar. (Reproduced from Terrett, The Emergency, 126.)

Still not wanting to depend entirely on Signal Corps radar equipment, in May 1941 the War Department entered into a secret contract 

with the Canadian government (being part of the British Commonwealth) to produce 100 copies of the RAF’s amazing GCI sets. President Roosevelt insisted that four sets be positioned in Panama, thus 

increasing the order to 104 sets. The Canadian-produced sets were 

given the Signal Corps designation “SCR-588” and were delivered 

without height-finding capability. Consequently, they could not be 
68 │ THE ARMY AIR FORCES TAKE CHARGE

used for GCI, which was the reason for building them in the first 

place. The Canadians began research on an improved version to solve 

this problem. However, as late as June 1942, only 10 improved SCR588B models would be delivered—testifying to the tremendous technical challenges of mass-producing GCI radar equipment.13

With frustrations building, the Signal Corps’s answer to the Air 

Corps’s desperate demands for detection equipment was that it took 

time to develop and build radar equipment and that all the Air Corps 

requests were on order. The Air Corps’s response was that AW units 

were already deploying without needed equipment. The heat of the discussions became intense. This logistics problem became so severe that 

this massive Air Corps–Signal Corps argument eventually drew in the 

Chief of Staff and resulted in the immediate retirement of the Chief of 

the Signal Corps, Maj Gen Joseph Mauborgne, in August 1941.14

In late 1941, the British Ministry of Aircraft Production finally released much-sought-after British radio and radar equipment, resulting in a host of assorted VHF radios and IFF sets to examine—plus a 

genuine GCI set with the amazing PPI scope. Using this one set as a 

model, the General Electric Corporation eventually produced over 

200 copies of the GCI radar, designated “SCR-527.” However, they 

did not start arriving in units until spring 1943.15

With considerable caution, the Signal Corps could now finally say 

that progress was being made. Even General Arnold seemed temporarily satisfied, annotating one Signal Corps report with “this looks 

OK to me.”16 There still were not enough radar sets for every unit requiring them, nor were there enough qualified technicians to operate 

or maintain them. However, critical radar equipment was finally beginning to arrive.

New Air Defense Mission and Organization

From the beginning, the ADC was only envisioned as a planning 

staff, having authority to help organize, coordinate, and test new air 

defense concepts but without actual operational control over either aircraft or AAA. Those functions resided in the First Army itself. Moreover, since attack against the continental United States was unlikely 

except by air, General Chaney of the ADC argued that Air Corps officers should play a leading part in this defense effort.
THE ARMY AIR FORCES TAKE CHARGE │ 69

In discussions within the Army, General Chaney proposed dividing the continental United States into four new regional defense commands, distinct from the four existing field armies that might deploy 

in wartime, thus leaving a region unprotected. Each defense command would have control over all regional elements of defense: 

ground troops, harbor defenses, pursuit aviation, AAA, and the aircraft warning service. If invaded, the defense command would become a theater of operations, and the defense commander would become the theater commander, with unified control over all military 

means within its theater.17

Agreeing with this concept, in March 1941, the War Department 

divided the United States into four defense commands—Northeastern, 

Southern, Central, and Western Defense Commands. The commanding general of each field army was also designated as the commanding 

general of the corresponding defense command to avoid parallel 

staffs.18 This same order also directed that the continental air defense 

mission in its entirety should now belong to the Army Air Corps 

rather than the field armies.19

While the Signal Corps was still responsible for installing and operating AWS equipment, it was now the Air Corps that would control 

and employ it. This change would result in a constant source of friction between these two members of the AWS team and would eventually become a major theme. The ties between the two corps would 

be close but constantly strained.

This enormous transfer of responsibility added to the Air Corps’s 

already tremendous growth, fueled by its urgent preparations for war, 

and created serious organizational problems for its chief of staff. 

Therefore, to better handle his new air defense responsibilities, General 

Arnold directed in March 1941 that the four former Army air districts become “numbered air forces,” or NAFs, the first use of this new 

organizational designation. Each NAF was to act as an intermediate 

echelon between each of the 17 aircraft wings located across the 

United States and the Air Corps headquarters, providing a clearer 

organization of continental air defense efforts. These four were designated First Air Force (in the former Northeastern Air District), 

Second Air Force (in the former Northwestern Air District), Third 

Air Force (in the former Southern Air District), and Fourth Air 

Force (in the former Southwestern Air District) and were geographically collocated with the four existing continental field armies.20
70 │ THE ARMY AIR FORCES TAKE CHARGE

In April 1941, the Air Corps further directed that each new NAF 

should divide its forces into two new subordinate commands, to be 

called “bomber commands” and “interceptor commands,” to organize their offensive and defensive capabilities better. Each interceptor 

command was specifically responsible for the aircraft, AAA batteries, 

and searchlight units for that region. The following month, the Air 

Corps completed its air defense restructuring by directing each of the 

four NAFs to establish and operate their own regional aircraft warning service under the direct control of each interceptor command.21

The interceptor commands were redesignated “fighter commands” in 

May 1942 when all pursuit groups and squadrons were also redesignated “fighter.”22

Eventually, the four NAFs divided their areas of responsibilities into 

18 different air defense sectors, each with its own information center:

• I Interceptor Command had its headquarters in Boston, and 

sector headquarters located in Philadelphia, New York City, 

Newark, New Jersey; and Norfolk, Virginia.

• II Interceptor Command had its headquarters in Fort Lawton, 

Washington, and a sector headquarters located in Portland, Oregon.

• III Interceptor Command had its Atlantic regional headquarters 

in Wilmington, Delaware, with sector headquarters located in 

Charleston, South Carolina; and Jacksonville, Florida. Its Gulf 

Coast regional headquarters was in Tampa, Florida; with sector 

headquarters located in Miami, Florida; Mobile, Alabama; New 

Orleans, Houston, and San Antonio, Texas.

• IV Interceptor Command had its headquarters in Los Angeles, 

with a sector headquarters located in San Francisco.23

Then on 20 June 1941, in an historic airpower reorganization, the 

War Department created the US Army Air Forces (AAF), commanded by General Arnold. It was an entirely new air organization 

comprising both the Air Corps, responsible for the support and training air commands, and an operational arm, the AAF Air Force Combat Command—a redesignation of the former General Headquarters 

Air Force—composed of the NAFs (figs. 5-3 and 5-4).24
THE ARMY AIR FORCES TAKE CHARGE │ 71

MILITARY DEFENSES

War Department

Chief of Sta

GHQ Chief, AAF

Field Armies

First Army

Second Army

ird Army

Fourth Army

Defense

Commands

Northeastern

Central

Southern

Western

Air Force

Combat Command

First Air Force

I Interceptor Command

Second Air Force

II Interceptor Command

ird Air Force

III Interceptor Command

Fourth Air Force

IV Interceptor Command

{

{

{

{

Figure 5-3. War Department reorganization, June 1941. (Reproduced 

from Wesley Frank Craven and James Lea Cate, eds., The Army Air 

Forces in World War II, vol. 6, Men and Planes [1955; new imprint, 

Washington, DC: Office of Air Force History, 1983], 87, http://media.

defense.gov/2010/Nov/05/2001329891/-1/-1/0/AFD-101105-019.pdf.)
72 │ THE ARMY AIR FORCES TAKE CHARGE

Defense Command

Air Force

Fighter Command

(Planes assigned) (No planes assigned)

Air Defense Wing Air Defense Region

Fighter Group

(or Groups)

plus

Fighter Control

Squadron

AWS Net

(Signal Corps

troops and 

civilians)

AA Units

Barrage

Balloons

Smoke

Generating

Units

AWS

Net

AA Units

Barrage

Balloons

Smoke

Units

Figure 5-4. AAF air defense organization. (Reproduced from Craven 

and Cate, eds., Men and Planes, 94.)

Long the goal of airmen in the Army, the formation of a more autonomous Army Air Forces now gave the evolving AWS a commandand-control connection to its superior interceptor command. Also, 

the new AAF established its air staff, on which it appointed its firstever director of air defense, the now-colonel Gordon P. Saville.25

Advanced Radar Training

In April 1941, Dr. James Conant, the president of Harvard University and an advisor on a host of classified technical programs, including the Manhattan Project, proposed a separate Electronic Training 
THE ARMY AIR FORCES TAKE CHARGE │ 73

Group (ETG), composed of Signal Corps and Air Corps officers with 

advanced engineering backgrounds. The ETG was to be gathered and 

sent to England to study in detail RAF Chain Home radar operations. 

The ETG was quickly established as a special part of the Signal Corps 

School. After completing basic training at Fort Monmouth, the selected 

officers were sent to Boston for several months to learn the electricalengineering principles of radar at Harvard and their practical applications at the Massachusetts Institute of Technology. By the end of 1943, 

when the ETG program was finally discontinued, nearly 1,000 officers 

had received this intensive and highly selective technical training.26

In July 1941, the first class of 35 ETG officers began their introduction to radar, which they completed by September. Then the ETG 

officers were sent on to Britain. They either continued with advanced 

radar courses taught by British engineers or were assigned to Chain 

Home stations to observe air defense operations firsthand. After 

serving several months with the RAF, most of the officers returned to 

the Unites States as either expert radar planners or to train new AWS 

units. The ETG training proved to be a critical step for the United 

States to quickly gain much needed operational experience in the 

new art of radar warning and control.27

Due to the increasing numbers of AW units being prepared for 

overseas deployment, the demand for AWS training finally grew so 

large it quickly threatened to exceed the capacity of Fort Monmouth’s 

Signal Corps School. What was needed was for the AAF and the Signal Corps to more equally share the burden of AWS training. During 

fall 1941, it was decided all Air Forces AWS training would be consolidated at a new Aircraft Warning Unit Training Center (AWUTC) 

to be built at Drew Field near Tampa, Florida.28 This new school 

would soon become the largest training center of aircraft warning 

troops and units in the AAF, training over 6,000 AW troops at any 

one time.29

The new AWS Department at AWUTC had a staff of two officers 

and 12 enlisted men who were responsible for training all information 

and filter center specialists: the plotters, tellers, filterers, raid clerks, 

and so on. The new Radar Department, consisting of 19 officer and 

114 enlisted instructors, conducted various SCR-268 and SCR-270 

training laboratories for scope operators, radar maintenance men, 

power plant mechanics, platoon chiefs, and so forth.30

Thus, all AWS personnel now followed fixed curricula. After completing OCS, 20 percent of the officers were sent for advanced ETG 
74 │ THE ARMY AIR FORCES TAKE CHARGE

training in Boston, then on to Britain. Having completed their tour 

with the RAF, they returned to Camp Murphy’s radar school, joining 

the other AWS officers not requiring the ETG training. These officers 

also joined the enlisted radar technicians in studying the installation 

and maintenance of Army radar sets taught by Signal Corps instructors. After completing technical training, officer and enlisted personnel moved across Florida to Drew Field, where they joined enlisted 

plotters and tellers trainees to received three months training in actual 

air defense operations at AWUTC conducted by AAF instructors. 

Once this marathon of training was completed, trained officer and 

enlisted personnel were sent to their operational AWS units.31

Army Air Forces School of Applied

Tactics and “Trigger”

Based on the lessons learned by the ETG officers, it became evident that an advanced air defense school was needed—not to teach 

more technical theory concerning the radar equipment itself but to 

instruct pilots and ground controllers on the more critical topic of air 

defense command-and-control operations and employment. At the 

time, Third Air Force’s III Interceptor Command (III IC) was operating a school, located in Orlando, Florida, which trained their personnel from Third Air Force fighter units in combined air defense tactics. 

In his capacity as AAF Director of Air Defense, Colonel Saville ordered the III IC Interceptor School to conduct training of all AAF 

fighter pilot and controller personnel in air defense operations. The 

Interceptor School was renamed the Air Defense Operational Training Unit, then the Fighter Command School, and finally the Army 

Air Forces School of Applied Tactics (AAFSAT).32

The AAFSAT’s Control Division was responsible for providing instruction to both pilots and controllers about AWS operations, day 

fighter control, night fighter GCI, and AAA employment.33 The division developed standard operational procedures for AAF-wide use, 

produced tactical manuals, and tested radar equipment. It placed significant reliance on the use of “synthetic training devices”—simulated 

equipment and diorama tables—when aircraft were not available. Instructors were often exchanged with the Naval Radar Training School, 

located at St. Simons, Georgia. The Control Division also acted as the 
THE ARMY AIR FORCES TAKE CHARGE │ 75

AAF’s experts in radar employment and was called upon on numerous occasions to assist the Ground Radar Branch of the Air Forces 

Board on AAF radar development and training.34 The AAFSAT Control Division’s Controller Course qualified officers for fixed or mobile 

operations at the AAF fighter command level, with an air defense 

command, or in a tactical air force. The Controller Course eventually 

grew into a program of four separate courses:35

The Basic Controller Course

The Basic Controller Course was the first of these courses developed. It qualified officers to be intercept officers, also known as deputy 

controllers, primarily in mobile radar units. There was instruction in 

the theory and techniques of control, with particular emphasis on 

practice in synthetic and actual controlling of aircraft. Also, dioramas 

were built, and newly devised methods introduced, using the latest reports received from AW units deployed in combat theaters of operation. The course consisted of five weeks of academic training in Orlando followed by one week of actual field operations training at nearby 

Leesburg, Florida, using an operational SCR-527 British GCI-type radar set in a van for mobile control training. By the end of the war, 67 

classes totaling 1,336 graduates attended the Basic Controller Course.36

The initial class of student controllers was composed of men newly 

commissioned directly from civilian life and who had only two weeks 

of basic military training. Qualifications for controllers had been 

clearly defined, but the difficulty of obtaining the necessary personnel 

proved a problem. A very limited number of former pilots and World 

War I officers were available. Consequently, 40 men drawn from 

banks, the stock exchange, and reputable business firms were recruited 

and commissioned. These officers formed the nucleus of the first two 

courses. The initial class of 14 students began on 29 June 1942 and 

graduated on 8 August 1942. These 14 became the officially designated 

“aircraft controllers”—the forefathers of all USAF air weapons controllers, who are now known as air battle managers.37

The Advanced Controller Course

After several months, it was determined an additional training 

course was needed to enable aircraft controllers to go directly to the 

field to perform the duties of sector controllers with only minimal 

orientation in the theater of operations. The course was planned to 
76 │ THE ARMY AIR FORCES TAKE CHARGE

enable students to become familiar with the most advanced types of 

tactical problems of aircraft control. Additional training was given in 

the employment and capabilities of radar, communications equipment, fixed and mobile equipment, GCI, and searchlight control systems. The course consisted of an additional three weeks of academic 

and actual controller training. From November 1943 until May 1944, 

14 classes were conducted, graduating 174 sector controllers.38

The Identification Officer Course

This course consisted of four weeks of instruction in the theory of 

identification of target plots on filter room and operations room 

boards, navigation, flight plans, pre-plotting, weather, and so forth. 

When the last class graduated on 25 March 1944, 23 classes had been 

conducted, totaling 175 graduates. Also, five Women’s Army Auxiliary 

Corps officers were trained as identification officers.39

The GCI Control Course—“Trigger”

Unlike the Basic Controller Course, the techniques used for GCI 

were much more demanding because ground-controlled intercepts 

usually occurred at night. The first part of the course consisted of 

academic instruction in the tactics of night interception using radar 

control of airborne interception (AI)-equipped night fighter aircraft. 

An SCR-527 mobile GCI-type radar set was installed by the RAF at 

Winter Garden, Florida. The RAF also provided a GCI advisor and a 

copy of their controller training syllabus, used by their own RAF 

Controller Training Unit at Stanmore, UK.40

Experienced controllers underwent four weeks of GCI training, 

controlling a minimum of 50 (then later 100) live interceptions using 

Douglas P-70 “Night Hawk” night fighters flown by the 481st Night 

Fighter Operational Training Group. Initially, all GCI target missions 

were run at pre-set altitudes on a prearranged course. However, intelligence was arriving from England that German tactics had changed 

and night bombers were engaging in a considerable amount of evasive 

action. Therefore, the prearranged procedures were discontinued, and 

target aircraft were then encouraged to follow their own course—making 

the work for the student controller even more challenging.41

So great was the need for GCI-capable controllers that by the end 

of 1943 instruction was being conducted by the school on a 24-hoursa-day, 7-days-a-week basis. In January 1944, the 481st was transferred 
THE ARMY AIR FORCES TAKE CHARGE │ 77

to Hammer Field, Fresno, California. Without the night fighters, the 

AAFSAT GCI Course finally ended in June 1944. A total of 32 GCI classes 

were conducted, totaling 486 trainees, of which only 187 graduated—a 38 

percent pass rate—GCI controlling was hard!42 To support the night 

fighter training when the 481st was transferred to California, a small 

temporary GCI Control Course was established at Hammer Field. It 

functioned there until 1947, when all GCI training was transferred to 

the new USAF Controller Course, was set up at Tyndall Air Force 

Base, Florida, in February 1948.43 Overall, during World War II, more 

than 1,800 controllers were trained by AAFSAT to support a variety 

of AAF fixed continental air defense and mobile radar missions.

Notes

1. Terrett, Emergency, 172.

2. Ibid., 252.

3. Fourth Air Force, Defense Plans and Operations, 81.

4. Terrett, Emergency, 253.

5. Ibid., 256. 

6. Ibid.

7. Ibid., 269.

8. Ibid., 253.

9. Thompson et al., The Test, 29.

10. Thompson and Harris, Outcome, 469.

11. Terrett, Emergency, 255–7.

12. Ibid., 219.

13. Thompson et al., Test, 102.

14. Terrett, Emergency, 219.

15. Thompson et al., Test, 97.

16. Terrett, Emergency, 260. 

17. Greenfield, Palmer, and Wiley, Organization of Ground Combat Troops, 117. 

18. Conn, Engelman, and Fairchild, Guarding the United States, 28. 

19. Williams and Fellow, “Deployment of Army Air Forces,” 154.

20. Ibid. 

21. Williams, “Deployment of the Army Air Forces,” 154.

22. History, III Fighter Command, vol. 1, 2–3.

23. Conn, Engelman, and Fairchild, Guarding the United States, 63. 

24. Craven and Cate, eds., Men and Planes, 87.

25. Goss, “Air Defense of the Western Hemisphere,” 254.

26. Thompson and Harris, Outcome, 534.

27. Terrett, Emergency, 289.

28. History, III Fighter Command, vol. 2, 97.

29. Thompson and Harris, Outcome, 538. 

30. History, III Fighter Command, vol. 2, 97.
78 │ THE ARMY AIR FORCES TAKE CHARGE

31. Thompson and Harris, Outcome, 534–5. 

32. Schaffel, Emerging Shield, 41. 

33. History, Controller Training Program, Air Force Historical Research Agency 

(AFHRA) call no. 245.5058-5 1942–1945, Inferential Research and Indexing System 

(IRIS) no. 00156429, 4, microfilm roll 4454 (A2660), frame 1338–49 (PDF 1317–28).

34. Ibid.

35. Ibid., frame 1338–69 (PDF 1317–48).

36. Ibid., frame 1338 (PDF 1317).

37. First Class of Aircraft Controllers.

38. History, Controller Training Program, Controller Training Program,” 

AFHRA call no. 245.5058-5 1942–1945, IRIS) no. 00156429, 4, microfilm roll 4454 

(A2660), frame 1325–9 (PDF 1304–8).

39. Ibid. frame 1338–41 (PDF 1317–20).

40. Ibid. frame 1329-1330 (PDF 1308–9).

41. Ibid. frame 1331 (PDF 1310).

42. Ibid. frame 1331-1338 (PDF 1310–7).

43. USAF Unit Lineage and Honors History, 3625th Technical Training Squadron.
Chapter 6

First Fighter Control Squadrons Emerge

Formation of First Units

Until fall 1941, the effort to incorporate radar into an early-warning 

aircraft-detection system centered on the Battle of Britain–proven 

RAF model. With the development of radar by the Army Signal 

Corps, the Army had formed signal aircraft warning (SAW) companies and battalions to operate and maintain this highly technical 

equipment. Each unit was to establish an air warning network of 

fixed radar sets. The radars were interconnected by wire communications to an information center that plotted and reported radar contacts.1

 The American AWS functioned very much like the British 

Chain Home radar defense.

Throughout this initial development, Air Corps aviators were detailed to work with these Signal Corps units as the controllers. As 

flyers, they provided critical aerial combat and ground attack expertise and could understand the intercepting pilot’s viewpoint as they 

guided their aircraft. They spoke “air force” in a Signal Corps outfit. 

Once the air defense mission was transferred to the “Airmen” in 

March 1941, it was natural the AAF would begin thinking about 

forming mobile versions of the fixed SAW units.2

The original designation of these mobile units was “air corps 

squadron, interceptor control.” Later they became “interceptor control 

squadrons.” However, in May 1942, General Arnold renamed all pursuit and interceptor units as “fighter,” so radar control units became 

“fighter control squadrons” or FCS (fig. 6-1).3

 The mission of the FCS 

was the tactical control of fighter aircraft in either offensive or defensive operations. The FCS used a system of radar detection sets to locate and follow friendly or hostile aircraft, radio direction finding 

(D/F) trucks or towers to help identify where friendly aircraft were 

located, “homing” stations to help aircraft steer back to base, and VHF 

communications relay stations to allow two-way communications.4

VHF D/F took continuous bearings on aircraft radio emissions, especially airborne “pipsqueak” system, which radiated a signal once a 

minute. The bearings laid out on plotting boards at control centers 
80 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

served to track the planes in flight and enabled ground control officers 

to guide the planes by radio telephone (figs. 6-2, 6-3, and 6-4).5

Figure 6-1. “Historical Data.” (Reproduced from History, 11th Fighter 

Control Squadron, 24 March 1942–30 March 1944.) Declassified.
FIRST FIGHTER CONTROL SQUADRONS EMERGE │ 81

Figure 6-2. Direction finding truck. (Reproduced from History, 15th 

Fighter Control Squadron, March–May 1944.)

Figure 6-3. Direction finding operator. (Reproduced from History, 15th 

Fighter Control Squadron, March–May 1944.)
82 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

Figure 6-4. Operation plotters charting air tracks. (Reproduced from 

History, 15th Fighter Control Squadron, March–May 1944.)

Typically, the FCS was commanded by a major and had approximately 10 officers and 250 enlisted men assigned. Depending on the 

theater of operations, many of the FCS had Army Signal Corps SAW 

units attached to them to provide their critically needed radar and 

air/ground communications. Later in the war, however, the FCS 

proved itself to be self-sufficient and no longer was paired with supporting SAW companies. The standard Army FCS table of organization authorized headquarters administrative personnel, controllers, 
FIRST FIGHTER CONTROL SQUADRONS EMERGE │ 83

radio-A operators (radios), radio-B operators (radar), operations 

plotters, direction finding plotters, high frequency (HF) and very 

high frequency (VHF) radio monitors, HF and VHF radio repairmen, message center and teletype personnel, switchboard operators, 

linemen, technical supply troops, motor pool personnel, and even 

mess personnel. Having a mobile mission, the FCS was expected to 

move out and follow the war. It would set up a mobile fighter control 

center (FCC) that operated out of a truck to provide radio guidance 

to nearby fighters. However, an FCS with its FCC might be ordered to 

establish a theater fighter sector. The FCS would then be replaced by 

another incoming FCS unit. Communications were critical to fighter 

control—on the ground, between the FCS radar sets, radio units, and 

between the FCC and the fighter squadrons HQs and in the air, between 

FCC and airborne aircraft. Radar might have been the eyes, but it was 

the miles of cables and the HF/VHF radios that provided the nerves.6

FCSs usually were given the same number designation as their assigned fighter group. The very first FCS was not the “1st FCS.” That 

organization was not activated until January of 1942. Instead, the 

very first FCS was the 24th Air Corps Squadron, Interceptor Control, 

at Hamilton Field, California, activated on 21 October 1941. Men arrived from across the United States, and within a month, the unit’s six 

officers and 281 men were soon running the San Francisco Information Center, supporting the San Francisco Air Defense Wing.7

Next, on 1 November 1941, the 55th Air Corps Squadron, Interceptor Control, was activated at Portland Air Base, Oregon, to support the 55th Pursuit Group. It would later move north to McChord 

Field, near Seattle, Washington, to support the Seattle Air Defense 

Wing.8

 On 4 November, the 35th Air Corps Squadron, Interceptor 

Control, was formed, again at Hamilton Field. This unit soon sailed 

for the Burma–India Theater to operate under Tenth Air Force.9

 On 

14 November, the 52nd Air Corps Squadron, Interceptor Control, 

was activated at Selfridge Field, Michigan, part of the 52nd Pursuit 

Group. The unit soon moved to South Carolina, then North Carolina, 

and then eventually to Orlando, Florida, to support the newly organizing AAFSAT.10 On 20 November, the 20th Air Corps Squadron, 

Interceptor Control, was formed in Orlando for additional AAFSAT 

support.11 Finally, on 1 December 1941, the 54th Air Corps Squadron, Interceptor Control, was activated at Paine Field, Everett, Washington. The unit was ordered to Baton Rouge, Louisiana, then moved 

on to Florida to support the Orlando Air Defense Wing.12 Overall, by 
84 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

the end of World War II, nearly 70 FCSs were organized to help win 

the war.13 As can be seen, however, a week before America’s tragic 

entry into the war, the AAF had only activated six FCS units, all of 

which were still in the process of getting organized.

Initial Air Defense Deployments

From late 1937 onward, the threat to US national security, as 

viewed by both President Roosevelt and his Secretary of State, Cordell 

Hull, was that Germany, in combination with Japan, might achieve 

domination over Europe and Asia, wreck the British Commonwealth 

of Nations, and threaten the Western Hemisphere. In January 1939, 

with the specter of war looming larger over Europe, President Roosevelt 

warned the nation about the new range and speed of offense. Then, 

current German bombers could not strike directly from Europe to 

the United States. However, the aerial stepping stones between Norway and New England could be Iceland, Greenland, and Newfoundland, Canada. Likewise, the Germans could reach into the south 

Western Hemisphere from Brazil, via Africa. The Caribbean also 

constituted a U-boat and commerce-raider danger as its eastern approaches were poorly protected.14

In his request to Congress for additional defense appropriations 

for the fiscal year 1940, President Roosevelt enlarged upon these 

themes by identifying these new forms of attack, paying attention to 

offensive airpower. In the Pacific, the problem was primarily one of 

extending facilities in the territories of the United States. In the Atlantic, however, it meant acquiring basing privileges from Latin 

American and European nations. National defense was now to be 

thought possible through total hemisphere defense.15

At that time, the only US Army garrisons overseas were its small 

Panama, Puerto Rico, Hawaii, and Philippines departments. By 1941, 

the United States began backing up its hemisphere defense intentions 

by increased deployments of American troops to those departments 

deploying troops to other strategically critical locations. As a show of 

US resolve, Secretary of War Henry L. Stimson began the deployment 

of several task forces. In February 1941, Task Forces 1 and 2 were approved to deploy to the Caribbean, while Task Force 3 was to deploy 

to Newfoundland. Task Force 2 was sent to Jamaica in April, and an 

agreement with the Danish government was signed approving the 
FIRST FIGHTER CONTROL SQUADRONS EMERGE │ 85

deployment of US troops to Greenland. Later, in August, Task Force 4 

was dispatched to Iceland. With each of these task forces came its pursuit aircraft and AW companies; invariably the AWSs arrived without 

their scarce radar equipment.16 By the end of 1941—only two years 

after the War Department created its trial Signal Company, Aircraft 

Warning, Panama, radar unit—efforts were underway for the new 

AAF to build and deploy numerous air defense units around the globe.

Continental Air Defense

During fall 1941, the four theater interceptor commands worked 

feverishly to create a coastal radar net and operational AWS. Radar 

was made operational in San Francisco, Seattle, and in New York 

City—with the help of RCA Corporation technicians.17 Sites for 13 

radar stations along the East Coast had been picked, and eight stations 

were approaching completion by December. On the West Coast, 10 

radar stations guarded the 1,200 miles stretching from Seattle to San 

Diego. However, there were not enough trained personnel to operate 

the equipment, no GCI radar capability, no VHF radio sites, and no 

identification-friend-or-foe sets (fig. 6-5).18

Figure 6-5. Philadelphia Information Center, 1940. (Reproduced from 

Wesley Frank Craven and James Lea Cate, eds., Army Air Forces in 

World War II, vol. 1, Plans and Early Operations [Chicago: University of 

Chicago Press, 1950], 289.)
86 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

Caribbean Air Defense

At the same time, the War Department was organizing its continental air defense efforts. Plans were also being made to unite the 

Panama Canal Department, the Puerto Rico Department, and several 

British islands under a new, single Caribbean Defense Command 

(CDC).19 Headquarters for CDC were established at Quarry Heights, 

Panama, across from Albrook Field and the pursuit planes of the 19th 

Composite Wing. By summer 1941, Puerto Rico’s San Juan Information Center had one SCR-270 operating 24 hours a day. It also had 

three SCR-271s on hand, but they were not operational due to lack of 

parts.20 By November, the Signal Company, AW, Panama, had two 

operational radars in service, an SCR-270 at each end of the canal, 

operating 24 hours a day (fig. 6-6).21

Figure 6-6. SCR-270 mobile radar in Panama. (Reprinted from Rebecca 

Robbins Raines, Getting the Message Through: A Branch History of the U.S. 

Army Signal Corps [Honolulu: University Press of the Pacific, 2005], 234.)

North Atlantic Air Defense

Establishing a secure air route to Great Britain was one of the War 

Department’s highest priorities, so the first Air Corps forces began ar-
FIRST FIGHTER CONTROL SQUADRONS EMERGE │ 87

riving in Newfoundland in October 1940. Acting as the staging point 

for most of the aircraft traffic to Europe, Task Force 3’s critical Newfoundland Aircraft Warning Service had three SCR-270s in operation 

by spring 1941.22 Meanwhile, one officer and 26 enlisted men of the 1st 

Aircraft Warning Company, fresh from Fort Hancock, New Jersey, arrived at Greenland’s Bluie West Army Air Field in July 1941. They were 

to begin convoy and ferry aircraft protection and to support friendly 

forces patrolling against Luftwaffe overflight. The overflights were facilitating the establishment of weather stations to support German operations in the North Atlantic.23 Germany staged several air attacks 

against the British forces stationed in Iceland in February 1941. Responding to these attacks, 30 P-40s of the 33rd Pursuit Squadron arrived 

in Reykjavik at the end of August with its 33rd Aircraft Warning Company and several SCR-268s and SCR-270s. Task Force 4 had a 24-hour 

fighter control room in operation by that fall, and by December, three 

RAF radar stations had been deployed and were operational (fig. 6-7).24

Figure 6-7. SCR-268 radar in Greenland. (Reproduced from Thompson, Harris, Oakes, and Terrett, The Test, 292.)

Alaskan Air Defense

In February 1941, all US troops in Alaska, under the Alaskan Defense Force, were now renamed the Alaska Defense Command. That 

same month, the 18th Pursuit Squadron, flying P-36s, arrived at Elmendorf Field to work with B-18 bombers. The next month, the Signal 
88 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

Company, Aircraft Warning, Alaska, arrived at Fort Richardson.25

The Alaska Defense Command consisted of only 143 troops, a dozen 

or so aircraft, and no radar sets for its AW company. The Army had 

intended to develop an AWS in Alaska as soon as it could, having 

begun work back in summer 1940. By October, a new plan had been 

approved, calling for 20 stations to be built throughout Alaska. However, by December 1941 none of them were completed or in operation. The overall goal had been too optimistic. No one had realized 

what a tremendously difficult job it would be to install and maintain 

radar sets in such rugged, isolated locations.26

Philippines Air Defense

With the threat of Japanese attack imminent, the War Department undertook a massive effort to accelerate the delivery of 100 

new aircraft—B-17 and B-24 bombers and P-35 and P-40 fighters—

to the Far East Air Forces for the defense of the islands. The Signal 

Company, Aircraft Warning, Philippines Department, arrived in August of 1941 to Fort William McKinley, in Manila, but without any 

AW equipment.27 However, by October, a single SCR-270 radar had 

been established at Iba Field, 75 miles northwest of Manila. Although 

seven radar sets had reached the Philippines by December 1941, only 

two—one at Iba and another one outside Manila—were operational.28

Hawaiian Air Defense

The Signal Company, Aircraft Warning, Hawaii, had 13 officers 

and 348 enlisted men, under the command of Capt Wilfred Tetley.29

The company operated a rudimentary information center at Fort 

Shafter in the hills above Honolulu. The unit’s first SCR-270s had arrived in July 1941, and by September, five sets were operating around 

the rim of Oahu. A sixth, at the Opana site on the northern point of 

Oahu at Kahuku Point, had just joined the AWS in November and 

had a range of approximately 75–125 miles seaward. Exercises that 

same month had detected aircraft carrier aircraft operating at 80 

miles out to sea. However, due to a shortage of spare parts, most radars were only operated from 0400–0700 hours daily, when the concern for an attack seemed the greatest (fig. 6-8). Understanding that 

an AWS was critical, the operations officer of the Hawaiian Interceptor 

Command, Col Kenneth Berquist, and his Signal Corps officer, Lt Col 

Carroll Powell, visited the mainland to witness a IV Interceptor 
FIRST FIGHTER CONTROL SQUADRONS EMERGE │ 89

Command AWS exercise. They returned to Hawaii on 4 December 

1941 to begin building their aircraft warning system.30

Figure 6-8. Opana Radar Station. (Reproduced from Andrew McKinley 

“The Opana Radar Station: Before the Attack,” Pearl Harbor Visitors Bureau, 2 June 2016, https://visitpearlharbor.org/the-opana-radar-station/.)

Overall, the building of new overseas air defense aircraft warning 

services had been a monumental task and was just in its infancy. 

Nothing like it had ever been attempted before by the Army, on such 

a large scale, over such global distances. Having established a tentative early warning and pursuit fighter capability in the Caribbean, 

North Atlantic, the Philippines, to some extent in Alaska, but certainly in Hawaii, the War Department air defense planners were optimistic these early efforts had been successful. On 7 December 1941, 

they would be proven terribly wrong.
90 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

Radar and the Attack on Pearl Harbor

On that Sunday morning, two trucks and a trailer holding the 

SCR-270 radar were parked on Opana Hill. Parked parallel to each 

other, the trucks contained the transmitter, receiver, oscilloscope, 

and operator equipment. On the trailer was mounted the 50-foot tall 

radar antenna.31

Suddenly, at 0702 hours, Pvt George Elliott and Pvt Joseph Lockard, practicing with their radar set, detected many aircraft approaching Oahu from the north. Elliott and Lockard quickly reported their 

findings to the information center at Fort Shafter. However, since this 

report arrived after the designated 3-hour watch time, most of the 

information center staff had already gone to breakfast. On duty that 

morning was Lt Kermit Tyler, a pilot with the 78th Pursuit Squadron, 

on loan from Wheeler Field. He had been in the information center 

only once before. After receiving Lockard’s report, Tyler reasoned the 

radar returns were a flight of Army B-17s arriving from San Francisco that morning. As a result, Tyler instructed the Opana radar unit 

to disregard the returns and to not worry about it.

Intrigued, Elliott and Lockard continued to plot the incoming aircraft until 0740 hours, when they lost the contacts. They then secured 

their radar equipment and headed down the hill for breakfast. It was 

only upon arriving for breakfast that the learned the Japanese air attack was under way (fig. 6-9).32 Overall, this was more of a failure of 

organization than of technology. The radar had successfully detected 

the incoming Japanese fighters, and Privates Elliott and Lockard had 

correctly detected and reported them. However, the immature Hawaiian AWS had not successfully functioned as an integrated air defense 

system, superiors had not been informed, and Army aircraft were not 

scrambled to engage the enemy—in fact they remained on the ground 

and were destroyed during the sudden attack.

Conclusion

Despite this early failure, the importance of radar detection and the 

need for an AWS to quickly and accurately alert air defense forces was 

immediately recognized. The use of this invention called radar gave a 

protecting force the ability to mount a timely defense against an enemy air attack. The theoretical concept of using radio frequencies to 
FIRST FIGHTER CONTROL SQUADRONS EMERGE │ 91

detect aircraft had become a reality in just 10 years. The “science” of 

radar and the “art” of air defense were combined in this way. The 

story of the beginnings of radar and fighter control is made up of innovative and persistent individuals, of teams of engineers building a 

vision, and of professional military officers in a race to employ a fantastic new technology to face a rapidly growing threat.

Figure 6-9. Opana radar plot, 7 Dec 1941. (Reproduced from Thompson, Harris, Oakes, and Terrett, The Test, 8.)
92 │ FIRST FIGHTER CONTROL SQUADRONS EMERGE

Notes

1. Terrett, Emergency, 150.

2. Craven and Cate, Army Air Forces in World War II, vol. 6, Men and Planes, 154.

3. Ibid., 307.

4. Terrett, Emergency, Signal Corps Equipment Appendix, 307–42.

5. Thompson and Harris, Outcome, 648.

6. Terrett, Emergency, 149–50.

7. History, 23rd Fighter Control Squadrons (FCS), Air Force Historical Research 

Agency (AFHRA) call no. SQ-FI-CONTL-24-HI October 1941–February 1944, 

“Headquarters 4th Air Force General orders No. 49,” 21 October 1941, and 1, microfilm roll 0879 (A0830), (PDF frames 460–61).

8. History, 55th FCS, AFHRA call no. SQ-FI-CONTL-55-HI November 1941–

September 1942, “Organization History,” 30 September 1942, microfilm roll 0881 

(A0832), frame 685 (PDF frame 651).

9. History, 35th FCS, AFHRA call no. SQ-FI-CONTL-35-HI November 1941–

August 1944, “Organization History,” 13 January 1943, microfilm roll 0879 (A0830), 

(PDF frame 838).

10. History, 52nd FCS, AFHRA call no. SQ-FI-CONTL-52-HI June 1943, “Unit 

History,” 1 July 1944, 39, microfilm roll 0879 (A0831), frame 1691 (PDF frame 1573).

11. History, 52nd FCS, AFHRA call no. SQ-FI-CONTL-52-HI June 1943, “Annex A-1 to Field Order 270,” 85th Fighter Wing, 1, microfilm roll 0878 (A0829), 

(PDF frame 1907).

12. History, 54th FCS, AFHRA call no. SQ-FI-CONTL-54-HI December 1941–

January 1944, “History,” 17 January 1944, 1, microfilm roll 0881 (A0832), frame 548 

(PDF frame 518).

13. Fighter Control Squadrons, USAF Historical Division.

14. Cate, “Air Corps Prepares for War,” 118.

15. Ibid.

16. Terrett, Emergency, 208.

17. Prange, Pearl Harbor, 366.

18. Goss, “Air Defense,” 290–91.

19. Conn, Engelman, and Fairchild, Guarding the United States, 329.

20. Terrett, Emergency, 299.

21. Prange, Pearl Harbor, 366.

22. Terrett, Emergency, 281.

23. Cate, “Air Corps Prepares for War,” 122.

24. Terrett, Emergency, 279.

25. Ibid., 208.

26. Conn, Engelman, and Fairchild, Guarding the United States, 245–57.

27. Hoyt, Airmen, 41.

28. Williams and Fellow, “Deployment of Army Air Forces,” 186.

29. Terrett, Emergency, 305.

30. Conn, Engelman, and Fairchild, Guarding the United States, 167–68.

31. Butowsky, “Opana Radar Site,” 4. http://focus.nps.gov/pdfhost/docs/NHLS/

Text/91001379.pdf.

32. Ibid., 8–9.
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A career air battle manager, Mr. Randall DeGering flew over 

2,700 hours aboard the E-3 Airborne Warning and Control 

System (AWACS) aircraft conducting real-world theater air 

control operations around the world. He currently serves at 

Headquarters North American Air Defense Command as an 

air defense radar analyst. In 1992, then-Captain DeGering 

completed this research monograph under a scholarship 

awarded by the Arr force Historical Research Agency. 

Now, 25 years later, retired Lieutenant Colonel DeGering's 

outstanding research effort is finally available in book form 

for a much wider audience. 

The biggest problem of modern fighters was intelligence. Without a continuous stream of 

accurate information keeping the fighters posted on exactly where the high-speed 

bombers were, attempts at interception were like hunting needles in a limitless haystack. 

-Capt Claire "Flying Tigers"Chennault

During the 1930s, as World War II approach�. the US Army began an urgent effort to 

construct an effective air-defense strategy. Its greatest problem-how to quickly 

detect approaching enemy bombers, then accurately control interceptors to the 

bombers before targets were attacked? 

The solution-radar! First developed by the British Royal Air Force in the 1930s, this 

new, top secret, and utterly amazing technical capability would provide the operational intelligence so desperately needed by newly forming Army Air Forces fighter 

control squadrons. 

How was radar first developed? When was it first employed to direct fighter aircraft 

against approaching enemy air forces? Could the Army Signal Corps duplicate the 

RAF's technical achievement? How did the Army Signal Corps and Army Air forces 

work together to develop the nation's first air warning services? Could radar sets be 

delivered to radar units in time for the approaching war? In his well-researched book, 

the author outlines the beginnings of Army radar development and its first operational uses for tactical fighter control. 

https:/twww.airuniversity.af.edu/AUPress/ 

ISBN 978-1-58566-291-3