page_title: Radar in World War II
section_title: Japan
hierarchical_section_title: Radar in World War II / Japan
context_page_description: Radar in World War II greatly influenced many important aspects of the conflict. This revolutionary new technology of radio-based detection and tracking was used by both the Allies and Axis powers in World War II, which had evolved independently in a number of nations during the mid 1930s. At the outbreak of war in September 1939, both Great Britain and Germany had functioning radar systems. In Great Britain, it was called RDF, Range and Direction Finding, while in Germany the name Funkmeß was used, with apparatuses called Funkmessgerät.
  By the time of the Battle of Britain in mid-1940, the Royal Air Force had fully integrated RDF as part of the national air defence.
  In the United States, the technology was demonstrated during December 1934, although it was only when war became likely that the U.S. recognized the potential of the new technology, and began development of ship- and land-based systems. The first of these were fielded by the U.S. Navy in early 1940, and a year later by the U.S. Army. The acronym RADAR was coined by the U.S. Navy in 1940, and the term "radar" became widely used.
context_section_description: In the years prior to World War II, Japan had knowledgeable researchers in the technologies necessary for radar; they were especially advanced in magnetron development. However, a lack of appreciation of radar's potential and rivalry between army, navy and civilian research groups meant Japan's development was slow. It was not until November 1941, just days before the attack on Pearl Harbor, that Japan placed into service its first full radar system. In August 1942, U.S. marines captured one of these first systems, and, although crude even by the standards of early U.S. radars, the fact the Japanese had any radar capability came as a surprise. Japanese radar technology was 3 to 5 years behind that of America, Great Britain, and Germany throughout the war.
  A major leader in early technology development was Hidetsugu Yagi, a professor and researcher of international status. His papers in the late 1920s on antennas and magnetron design were closely studied by scientists and engineers worldwide. He was allowed no part, however, in developing Japan's wartime radars. His earlier work was given so little attention by the Japanese military that, when they received a captured British radar set, at first they were unaware that the "Yagi" mentioned in accompanying notes referred to a Japanese invention.
  Although Japan had joined Nazi Germany and Fascist Italy in a Tripartite Pact in 1936, there had been essentially no exchange of technical information. This changed in December 1940 when a group of Japanese officers representing Army technology was allowed to visit Germany, followed in January by a similar group from the Navy. In the visit, the Japanese were shown some German radars and a British MRU (their earliest searchlight-control radar), left behind during the Dunkirk evacuation. In addition, German-educated Yoji Ito, leader of the Navy delegation, was able to obtain information from the host on the MRU's pulsed operation. Ito immediately sent this information home by diplomatic courier, and work was started by the Navy on Japan's first true radar.
  After war was started with the United States in December 1941, the Germans shipped a Würzburg radar to Japan. The submarine carrying this equipment was sunk on the way, and a second set met the same fate; however, some key hardware and documentation, sent on a separate vessel, made it safely.
  When Singapore was taken by Japan in February 1942, the remains of what turned out to be a British GL Mk-2 radar and a Searchlight Control (SLC) radar were found. Along with the hardware, there was a set of hand-written notes, giving details of the theory and operation of the SLC. At Corregidor the following May, the captors found two U.S. Army radars, an SCR-268 in operating condition and a heavily damaged SCR-270. In a rare cooperative effort, the Army and Navy jointly conducted reverse engineering on these sets.
  About 7,250 radar sets of 30 different types were developed for the Army and Navy.
caption: Nakajima J1N night fighter with FD-2 nose radar
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