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. Imperial Army The Tama Technology Research Institute (TTRI) was formed by the Army to lead in what was called Radio Range-Finder (RRF) development. TTRI was staffed with competent personnel, but most of their developmental work was done by contractors at the research laboratories of Toshiba Shibaura Denki (Toshiba) and Nippon Electric Company (NEC). The TTRI established a system for designating the Army radar equipment, based on its use. The prefixes were Ta-Chi (written herein as Tachi) for land-based systems, Ta-Se for shipborne systems, and Ta-Ki for airborne systems. The "Ta" denoted Tama, the "Chi" was from tsuchi (earth), the "Se" means mizu (water) rapids, and "Ki" was from kuki (air). In June 1942, both NEC and Toshiba started projects based on the SCR-268. The American system operated at 1.5 m (200 MHz). It had a very complex set of three antennas on a horizontal, rotatable boom and used lobe switching. The NEC project was for a target-tracking system designated Tachi-1, essentially a copy of the SCR-268. The duplication of this system was found to be too difficult, and Tachi-1 was soon abandoned. At Toshiba, the project was also for a target-tracking system designated Tachi-2. This was to incorporate many simplifications to the SCR-268. Preliminary tests showed that it would be too fragile