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Overview: the Signal Corps in World War II

by George Raynor Thompson

World War I had been a one-theater conflict, whose communications needs the Signal Corps met with sudden growth — from fewer than 2,000 officers and men to more than 60,000. The magnitude of the second world war, however, was much greater. The corps mushroomed from a strength of 27,000 at the war's outset to about 350,000 men supporting the U.S. Army in theaters all around the globe.

Great as this expansion in manpower was, greater yet were new equipment developments and mass production of wire and cable, radio radar, and all the increasingly complex components of modern communications-electronics.

More than any conflict before it, World War II became a war of materials and machines, of tanks and vehicles of all sorts, and of the equipment that goes with motorized land operations, with aircraft and their specialized needs, and with all the communications equipment required to coordinate men and their machines.

These circumstances demanded enormous quantities and elaborations of C-E components, requiring large development laboratories (chiefly at Fort Monmouth, N.J., and Dayton, Ohio), huge procurement and supply organizations, not to mention a manyfold expansion of the nation's electric manufacturing plants.

World War II also placed upon the Signal Corps enormous training requirements for unheard-of numbers of skilled soldier-operators of C-E equipment, as well as for troops to supply and distribute the equipment, to install it, and then to attend to its maintenance and repair. All these tasks in the Army were the responsibility of the Signal Corps. Such was the magnitude of the need and the responsibility.

War's outset

Yet, during the depression decade of the 1930s, the Army's communications equipment and techniques had fallen behind the new requirements of mobility, range and reliability for the growing needs of motorized infantry, artillery and armor — not to mention the pressing demands of air-to-air and air-to-ground communications and of radar.

Light tanks in New Guinea Light tanks in New Guinea. The Signal Corps designed communications systems for the U.S. Army's armored force before World War II's onset under MG Adna Chaffee's direction.

But the Signal Corps' leaders were aware of the needs. MG Joseph Mauborgne, a research-minded Chief Signal Officer during 1937-41, gave strong support to Army radar, which Col. William Blair, director of the Signal Corps' laboratories at Fort Monmouth, had initiated. (Blair received a basic patent for the first Army radar demonstrated in May 1937).

Mass production of two radar sets — the SCR-268 (designed to direct searchlight beams upon aircraft), and the SCR-270 (a mobile long-range aircraft detector, or early-warning set) — had begun before the nation entered the war. A SCR-270 on Oahu detected the approach of Japanese aircraft the morning of Dec. 7, 1941 — picking up the planes' echoes when they were 130 miles away and giving the warning no one would believe.

Months before Pearl Harbor, radar developments, especially for the Army Air Forces, began to press the Signal Corps. Developing and producing superior microwave radars was made possible by the British cavity-magnetron transmitter tube — which our allies brought to us in greatest secrecy in 1940, seeking engineering and manufacturing assistance of microwave radars in quantity. This led to the expansion of radar research-and-development facilities in the military services, in universities and in industry. Dozens of Army ground and airborne radar types were developed and produced under Signal Corps supervision.

Outstanding among the ground sets was the microwave SCR-584, a superlatively accurate gun director. It was first used in combat at Anzio, Italy, in 1944, where antiaircraft artillery, directed by the SCR-584, devastated German air attacks. A little later, this radar was the decisive element in smothering the buzz-bomb attacks on England, where accurate SCR-584-controlled gunfire destroyed most of the V-ls in the sky.

Corps innovations

Army radar, though it became a billion-dollar baby, constituted but a part of Signal Corps equipment tasks. Communications, wire and radio, stood foremost. Communications — that is, reliable heavy-duty message and voice traffic — had previously meant telegraph, teletype and telephone transmission over wire or cable circuits. But now mobile warfare, requiring communications links to every moving tank, command car and airplane, meant radio circuits must also be heavily relied on.

Radio use previously had not compared well with wire, either in reliability or in clarity. Fortunately, the solutions to problems in tactical radio for ground vehicles had been worked out in the 1930s by the renowned electronics scientist, Maj. Edwin Armstrong, when he invented FM radio. Armstrong of course had served the Signal Corps brilliantly in France during World War I where, among other contributions, he had developed the first superheterodyne receiving sets.

Late in the 1930s, the Signal Corps labs, under Col. Roger Colton working with Armstrong, developed the first pushbutton crystal-controlled FM tactical radios (Armstrong donating his time, his radio equipment and his patents voluntarily). Crystal control of every channel eliminated fussy dial-tuning, so unskilled, harried soldiers could talk over these voice radios simply by pushing a button.

This control, however, meant mining great quantities of rare quartz crystal and producing millions of precisely cut crystal frequency-control units. The radio industry had heretofore never imagined possible the production of more than a few thousand hand-fabricated units a year. The Signal Corps risked the chance that enough crystal units could be produced. More than 100 manufacturing companies, with the Army's aid, attacked and solved the intricate task of mass-producing the crystals and the highly complex pushbutton radios.

Tactical advantages

FM crystal-controlled sets elevated radio usage, making FM radio the equivalent of wire telephone communications — reliable, easy to use, usually easy to understand. Then, upon applying FM radio to radio-relay techniques, the inherently short range of VHF FM was extended, in 30-mile hops, to whatever distance circuits might be desired. This was done by relays of truck-mounted equipment, able to provide in a matter of hours long-distance, highly reliable multichannel circuits — much faster, much easier and less costly than erecting miles of wire lines.

Furthermore, all this superlative radio communications could be, and eventually was, interconnected into wire-line systems. As a result, wire and radio became married; their circuits were integrated, providing high-quality communications irrespective of whether signals traveled by wire or by radio, and alternatively over links of each.

The tactical FM radio of American armies became the envy of all nations in World War II combat — in tank warfare and in amphibious assaults, too, where the Navy and Marines eagerly sought the FM sets and relay, and also for ship-to-shore use. FM radio relay, AN/TRC-l, -3 and 4 (commonly called antrac in Europe and VHF in the Pacific), alone kept communications operating all the way forward during Gen. George Patton's 3d Army dash deep into France in 1944 after the St. Lo breakout.

The fast long-distance penetrations of the tank forces operated on a shoestring for days — the shoestring was the slender but vital radio-relay circuits which BG E.F. Hammond, Patton's signal officer, provided by employing 28 radio-relay truck units. These antracs and their operators kept Patton's headquarters, "Lucky Forward," in complete communications throughout the daily giant strides of Third Army combat forces.

In tactical combat, armored-force and artillery operators (also infantrymen using the walkie-talkie SCR-300) could talk and clearly hear over their FM sets, which remained free of the static and interference that bedeviled the other combatants' AM radios.

One American veteran of Siegfried Line combat wrote, "I know the fighting would have lasted longer if we hadn't had FM on our side. We were able to shoot fast and effectively because we could get information quickly and accurately by voice on FM."

He added, "FM saved lives and won battles because it speeded our communications and enabled us to move more quickly than the Germans, who had to depend upon AM."

Likewise, Col. Grant Williams, signal office of 1st U.S. Army, commented, "I feel every soldier who lived through the war with an armored unit owes a debt he does not even realize to General Colton." For it was Colton who had made the risky decision to commit Army tactical radio to FM and crystal control at a time when there was uncertainty if effective FM radio could be mass produced, if quartz crystal could be found in sufficient quantity, and if precise fabrication of the frequency-control crystal units could be converted to mass production.

Strategic communications

As in tactical radio, so too in Army worldwide strategic communications there occurred tremendous equipment innovations and expansions. Before World War II, a modest number of radio and wire circuits for military command and administrative communications had been extended over the continental United States, and beyond to a few outlying headquarters locations.

Underground switchboards near Bergstein, Germany A PFC from 8th Infantry Division operates BD-71 and -72 switchboards in parallel at Bergstein, Germany, Feb. 3, 1945.

The radio circuits were mostly hand-keyed, transmitting Morse code. Some employed higher-speed Boehme telegraph equipment. Messages had to be hand-enciphered and -deciphered before and after transmission for security. But these facilities and these methods were totally inadequate for the worldwide nets the Army and Army Air Forces required at once after Pearl Harbor — long-range, transoceanic, multichannel circuits, channeling massive flows of communications traffic around the clock, day after day.

The Army Communications Service, operating from the Office of the Chief Signal Officer in Washington, went to work at once in cooperation with the nation's commercial communications companies and quickly developed single- sideband radio facilities, spiral-four field cable and complexes of carrier equipment, which could be applied either to radio or wire lines and which permitted the transmission of several telephone or teletype communications simultaneously over a single circuit. Fast teletypewriter techniques were applied to radio usage, replacing the older, much slower hand-keyed or Boehme operations.

Above all, the Signal Corps developed new enciphering and deciphering machines which did their work automatically, synchronized with the teletypewriters at both ends of the circuits. Eliminating slow hand-ciphering or coding methods chalked up a major advance in World War II strategic communications.

WAR on the air

Beginning in 1942, ACS rapidly built up a huge semiautomatic global system called ACAN — Army Command and Administrative Net — which centered in station WAR in the Pentagon. The service simultaneously built up a second global net solely serving the Army Air Forces. This was called the AACS, or Army Airways Communications System.

Major ACAN stations were established — eastward in London; Algiers, Algeria; Cairo, Egypt; later in Caserta, Italy; in Paris; and by mid-1945 in Frankfurt, Germany. Other stations moved westward with the war's progress — from Hawaii to Noumea, New Caledonia; to Brisbane, Australia; to New Delhi, India; to Hollandia, New Guinea; and by 1945 to Manila, the Philippines; Okinawa, Japan; and finally to Tokyo at the war's end.

Between these eastward and westward ACAN links a major tie-in was established early in the war at Asmara in east Africa. The Asmara station, like a keystone in an arch, caught up and firmly bonded the other links into a global beltline of powerful, long-range, multichannel radio teletypewriter circuits.

It was called the beltline since the radio links composing it girdled the earth in latitudes near the equator. Signal Corps operators found high-frequency radio was much more dependable in tropical areas — freer from ionospheric interference and able to operate with a minimum of circuit outage. (Interference became progressively worse in latitudes farther north, worst of all in polar regions.)

All these massive ACAN facilities — plus the air-ferry communications of the AACS guiding aircraft across the North and South Atlantic, across Africa and the Near East, across the Pacific to the Far East — constituted a system of communications, the likes of which had never existed, or scarcely even been imagined possible before.

ACS chief MG Frank Stoner enjoyed reminding the Army that the commodity sent overseas in World War II was words, not bullets. He figured the proportion at eight words to every bullet. By 1945, ACAN capacity was 100,000,000 words a day. The average daily load amounted to about 50 million words.


The equipment, the facilities, comprised only one face, one side, of the Signal Corps coin. The other was the human side, the 350,000 officers and men and Women's Army Corps members. Training them by the tens of thousands constituted a staggering task. Sources of men with some C-E familiarity, or with electrical experience in industry, radio-repair shops, schools and colleges, or in radio amateur organizations, were soon exhausted. The majority had to be trained by the Army, generally from scratch.

The Signal Corps struggled to get as large a portion as possible of the more promising draftees, for rapid mastery of C-E skills could not be accomplished by those who stood low in AGCTs.

The established Signal Corps specialist schools and Fort Monmouth's replacement training center were bolstered by huge new camps such as Camp Murphy, Fla. (for radar training); Camp Crowder, Mo.; and Camp Kohler, Calif., for all types of C-E training. Under the corps' enlisted reserve program, students were enrolled in C-E courses at numerous colleges and institutions across the country.

Altogether, more than 30,000 officers graduated in some 50 different types of courses during the war. Enlisted men trained in C-E amounted to nearly 400,000. Many of the officers and men went into units serving the Army Air Forces.

More training was conducted in the overseas theaters of the war, notably in the Mediterranean area under BG R.B. Moran, signal officer of the Fifth Army, and under BG F.B. Ankenbrandt, signal officer in the South Pacific area.

Signal units

Signal units by the hundreds were activated — companies and battalions for operations and construction as in former wars, and also new and previously unheard-of types, such as aircraft-warning companies and battalions (for radar-warning services to the Army Air Forces), and radio-intelligence and SIAM companies to support the Signal Corps' large radio security and intelligence responsibilities. Then there were JASCOs, — joint-assault signal companies — created to meet the amphibious-assault communications needs of joint Army/Navy operations.

Unit requirements were so pressing, and often arose so suddenly, that students were taken out of the schools, their course work incomplete, to fill requirements in signal companies and battalions. These units were trained more in huge unit training centers, especially at Camp Crowder, or they continued training in assignments overseas, on the job.

Really skilled specialists were in highest demand. Specialist units were split time and time again to establish cadres, hard cores of completely competent men to serve as nuclei for new combat units or for instruction at training schools.

Signal photography

A major aid in mass-training the millions of America's unskilled soldiery, drawn from the peaceful pursuits of civilian life, was the training films-motion pictures provided by the Signal Corps Photographic Service centered at Astoria, Long Island. Hollywood producers lent much assistance, contributing, for example, animation techniques to enliven and lighten the heavy doses of instruction of thousands of reels of film.

Many people in civilian studios took commissions as Signal Corps officers — for example, Col. Darryl Zanuck and Maj. Frank Capra contributed their know-how to organizing and operating signal photographic companies that served in every theater of combat.

Combat photography (not a few lost their lives in this work) was in much demand for the Army's information and intelligence needs.

Shooting Allied activities near St. Vith, Belgium, in 1945 Signal Corps cameraman Sgt. Aaron Lubitsch wraps up shooting Allied forces' activities in St. Vith, Belgium, Feb. 10, 1945.

The task of logistics

Signal logistics — the production, storage and distribution of C-E equipment — occupied great numbers of military and civilian people. First among the major tasks was contracting with industry to produce massive quantities of communication end-items, components and spare parts. To bolster and expand the industry, Signal Corps logistics workers helped with the labor supply; they helped provide critical raw materials and they helped build up plant facilities and factories.

They received the equipment as it poured off assembly lines, moving it to depots for temporary storage. They received requisitions from Army users, filling the requisitions from the depots, shipping and distributing the equipment the world over — not to mention administering payment for it all.

Before World War II, the Signal Corps budget had been small. For example, the preliminary budget (drawn up in 1939) for fiscal year 1941 totaled $9 million. But, as a result of one war crisis after another in the emergency years, the funds Congress actually made available to the corps added up to $256 million.

Within six months after Pearl Harbor, by mid-1942, the Signal Corps had placed more than $2.5 billion worth of production contracts. A year later, the corps' budget stood at over $5 billion, about 1/20th of the total Army-Navy costs.

Signal Corps supply centered in the Philadelphia Procurement District and the huge Philadelphia Signal Depot. Other major signal depots in the United States were located in Boston; Baltimore; Dayton, Ohio; Chicago; Sacramento, Calif.; and Lexington, Ky.

In the theaters of operations, massive supply bases everywhere backed up the combat fronts — in England and North Africa, in Hawaii and the islands of the far Pacific. Theater signal officers enjoyed direct control over their own supply, giving them an advantage in providing the combat forces fast, responsive signal support that was the envy of our allies.

Post-war changes

Under MG H.C. Ingles, Chief Signal Officer from 1943-1947, the Signal Corps came through World War II larger — with wider activities and more responsibilities — than ever before. This was true despite the loss to the Army Air Forces late in 1944 of all responsibility for aviation C-E, and also despite the loss in late summer 1945 of all radio-intelligence activity.

Radio intelligence and security had grown greatly during the war because radio and radar use had expanded, and with expanded use came radio and radar countermeasures. The activity had required a large Signal Corps organization and dozens of radio-intelligence companies in all theaters of combat. The entire activity was transferred in September 1945 to the Army Security Agency.

Although these transfers stripped the Signal Corps of half its men and activities as of late World War II, almost within months after V-J Day, the corps acquired important new missions in the explosively expanding sphere of military C-E — which not only restored but in fact further enlarged the corps' stature within the Army.

Signal Corps achievements

In summary, the Signal Corps had entered World War II with relatively few officers and men, with utterly inadequate stores of equipment, with a skeletal training organization and with insufficient industrial backing. (The nation's electronic producers had little experience in mass-producing intricate military radio, almost none in radar). Yet the corps succeeded in the course of the war in creating a vast organization of skilled men, mountains of equipment and worldwide communications systems.

Signal Corps leaders "were walking on uncharted ground," in the words of MG James Code, the assistant signal officer in Washington headquarters. The job to be done seemed impossible, he added, saying, "We had no pattern to follow either in organization or in demands — we needed more equipment than the entire industry had ever turned out, more trained men than were available, or could be trained in the time allowed us, and we had to fill demands for weapons unheard of."

Yet all this was done. "A truly fantastic and wonderful job," Code concluded at the end of World War II.

Thus the Signal Corps developed, supplied, installed and maintained C-E for all the Army's ground forces and for that fast-growing, youngest Army element, the Army Air Forces. Practically all the Air Forces' C-E equipment throughout the war came from the Signal Corps, since separating the airmen's electronics from the corps did not happen until the very last months of the war.

Besides supplying all the airmen's C-E, the corps also met their voracious requirements for aircraft-warning troops and for great numbers of officers and men trained in every sort of communications specialty.

American ground-forces radio equipment — the handie-talkies (SCR-536), walkie-talkies (SCR-300) and larger, long-range, truck-mounted mobile SCR-299s and -399s — were unsurpassed. Above all, the short-range vehicular FM radios in the SCR-508 and -608 series (for armored force and artillery, respectively) gave our soldiers in combat a tactical voice-communications facility that excelled any equipment possessed by either the enemy or the Allied nations.

Signal Corps achievements in World War II were not confined to meeting its primary mission: assuring the communications which every commander had to have in order to control his forces. The corps also contributed much to civil progress in postwar years.

The war effort and its outpouring of funds helped boost the relatively small prewar electronic industry to a foremost place in the nation's economy. The Signal Corps contributed thousands of new developments and inventions to the nation's C-E technology.

And the corps returned into civilian employment after the war tens of thousands of the men and women it had trained in the new technologies of radar, radio teletype, radio relay, FM radio and other important areas. Thousands of these people continued to apply their advanced knowledge and skills to the nation's benefit and future progress for many years.

(Editor's note: This article was adapted from Story of the U.S. Army Signal Corps, edited by retired LTC Max Marshall, published by Franklin Watts Inc., New York, 1965. Used by permission. Dr. Thompson was formerly chief historian in the Office of the Chief Signal Officer, plus head of operations research and technical liaison of U.S. Army Strategic Communications Command.)

dividing rule

Acronym QuickScan
AACS — Army Airways Communications System
ACAN — Army Command and Administrative Net
ACS — Army Communications Service
AGCT — Army General Classification Test
AM — amplitude modulation
C-E - communications-electronics
FM — frequency modulation
JASCO — joint-assault signal company
SIAM — signal intelligence and monitoring
VHF — very-high frequency

Last modified on:
April 04, 2012

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This is an offical U.S. Army Site |
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