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The Defining Technology of World War II is RADAR

On Thursday, November 20, 1941, Thanksgiving Day, a new mobile electronic detection system was set up at Opana Point on Oahu, Hawai’i. Just days later, on December 7, 1941, Japan launched a surprise attack on Pearl Harbor, triggering the entry of the United States into World War II.  Prior to the attack, soldiers using the new Signal Corps early warning system successfully detected the incoming airplanes, and sounded a warning that could have changed the nature of that encounter.  But the technology they were using was so new, it didn’t even have a name yet, and their warnings went unheeded.  It was the first use of radar by the U.S. in war.

Scientists around the world had been experimenting for years with bouncing radio signals off of remote objects as a means of detection and location, but no viable system existed prior to the Signal Corps rollout of SCR-268 and SCR-270 (pictured above).  These systems were given radio device codes to preserve the highly confidential nature of this research.  The term “RADAR,” for “Radio Detection and Ranging,” was first coined by the Navy in 1941 and was accepted by the Army in 1942.  

Early Signal Corps radar systems required two sets of antenna, one for sending a signal, and another for receiving that signal after it bounced off of whatever was out there.  Over time, led by the man who would eventually be granted the U.S. Patent for radar, Colonel William R. Blair, head of the Signal Corps Laboratories at Fort Monmouth after Colton, these radar systems would use a single antenna, making  the entire system more easily transportable.  

Signal Corps radar systems were developed specifically to help airplanes hunt submarines, which helped turn the tide in the Allied battle against German U-boats.  Other radar systems were developed to track the origin location of mortar or artillery fire to enable infantry and armored units to mount an effective defense.  Radar systems were used in the Pacific theater to offset Japanese superiority in night fighting.  Fort Monmouth-designed radar sets landed on the beaches of Normandy on D-Day to detect Luftwaffe attacks.  As the Axis forces learned to jam early radar systems, the Signal Corps developed newer and better sets.  The SCR-584 radar system, developed at Fort Monmouth in 1942, could detect aircraft and determine their identity, becoming the first reliable “friend or foe” identification system.  By 1945, radar systems had been developed to include “fire control, early warning, ground control of intercept, navigation, gun laying, blind bombing, airborne interception, air-to-surface vessel detection, ground control of approach and weather monitoring.”  These and other successful applications are why many consider radar to be the defining technology of the Second World War era.  

While the research into these systems was conducted with the highest level of secrecy, once a radar system was ready to be deployed, the Army often contracted with companies such as Sperry Gyroscope and Western Electric for the manufacturing of these system or components.  And it was at this stage, as the technology moved from experimental to official military deployment status, that the details contained in manufacturing plans were vulnerable to theft by spies such as Julius Rosenberg, Joel Barr and Alfred Sarant, American-born engineers who stole valuable Signal Corps secrets on behalf of the Soviet Union in World War II.

Today, radar is a ubiquitous technology that affects everything from enabling airplanes to land in fog to precise weather forecasting.  Historians believe that radar was one of the key factors in England’s ability to win the Battle of Britain, and that whichever side in the Second World War had the best radar had the best chance of winning.  Luckily for the Allies, the best came out of Fort Monmouth.


Radosh, Ronald & Milton, Joyce.  (1983).  The Rosenberg File: A Search for the Truth.  Holt, Rinehart and Winston, New York, N.Y.

Staff of the Historical Office.  (2008).  A History of Army Communications and Electronics at Fort Monmouth, New Jersey 1917-2007.  Office of the Deputy Chief of Staff for Operations and Plans, U.S. Army CECOM Life Cycle Management Command, Fort Monmouth, N.J.  U.S. Government Printing Office, available:

Usdin, Steven T.  (2005).  Engineering Communism: How Two Americans Spied for Stalin and Founded the Soviet Silicon Valley.  Yale University Press, New Haven, Conn.

Usdin, Steven T.  (2007).  Tracking Julius Rosenberg’s Lesser Known Associates: Famous Espionage Cases.  Central Intelligence Agency Library, April 15, 2007.  Updated June 26, 2008.  Available:

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