Army Technical Research Institute (Tama Army Technical Research Institute)

The Army Technical Research Institute (陸軍技術研究所, Rikugun Gijutsu Kenkyūjo) was the Imperial Japanese Army's principal weapons research and development organization. Its origins trace to 1919, when the Army Scientific Research Institute (陸軍科学研究所) was established in the Toyama district of Shinjuku, Tokyo, to systematize military technology development. As Japan's military ambitions expanded through the 1930s, the cramped Toyama facilities proved inadequate.

In 1938, the Army began searching for a large tract of land along the Chuo Line west of Tokyo. They identified the Musashino Plain north of Musashi-Koganei Station — flat, expansive farmland in what was then rural Koganei-machi and Kodaira-mura. Between 1940 and 1942, the military compulsorily acquired approximately 175 hectares (530,000 tsubo) of agricultural land, displacing local farming families. Construction of a sprawling research campus commenced immediately.

By 1942, the complex housed multiple numbered research institutes, each with specialized missions:

• First Army Technical Research Institute (第一陸軍技術研究所): Firearms, ammunition, and equestrian equipment research (~900 personnel)
• Second Army Technical Research Institute (第二陸軍技術研究所): Observation, survey, and command-liaison equipment
• Third Army Technical Research Institute (第三陸軍技術研究所): Explosives, engineering weapons, and amphibious equipment (~500 personnel)
• Fifth Army Technical Research Institute (第五陸軍技術研究所): Communications equipment, maintenance materials, and electromagnetic-wave weapons (radar)
• Seventh Army Technical Research Institute (第七陸軍技術研究所): Basic physics research
• Eighth Army Technical Research Institute (第八陸軍技術研究所): Weapons materials — metals, rubber, and rare elements (~380 personnel)

The most historically significant development came on June 11, 1943, when the Army established the Tama Army Technical Research Institute (多摩陸軍技術研究所, Tama Rikugun Gijutsu Kenkyūjo) by consolidating the electromagnetic-wave weapons research divisions from the 5th, 7th, and 9th Army Technical Research Institutes along with radar sections from the 4th Army Aviation Technical Research Institute. This new institute, dedicated exclusively to radar and electronic warfare, became the Imperial Army's foremost radar development center.

The naming convention for all Army radar equipment derived directly from this institute: the prefix "Ta" (タ) stood for "Tama," combined with suffixes indicating platform — "chi" (チ, from 地/ground) for ground-based systems yielding "Tachi" (タチ), "se" (セ, from 船/ship) for naval systems yielding "Tase" (タセ), and "ki" (キ, from 機/aircraft) for airborne systems yielding "Taki" (タキ).

Among the most significant radar systems developed under the Tama Institute's direction were the Tachi-6 early warning radar, a deceptively simple floodlight system operating at 3-4 meters wavelength with a maximum detection range of 300 km — about 350 units were built, making it the Army's most widely deployed and reliable early warning radar. The Tachi-7 mobile variant entered service in 1943, followed by the lightweight Tachi-18 (approximately 400 units produced in 1944). For maritime use, the Tase-1 was developed for Army transport ships, and the Tase-2 provided anti-submarine search capability. The Taki-1, entering service in 1943, could detect large warships at 100 km and surfaced submarines at 20 km.

By war's end, the Tama Institute had developed or initiated research on an extraordinary total of 62 types of electromagnetic-wave devices: 17 ground-based, 17 airborne, 7 shipborne, 4 miscellaneous primary weapons, 14 secondary (derivative/auxiliary) devices, and 3 tertiary weapons. In a notable departure from military secrecy, the Army deliberately opened some of its radar research to civilian scientists and engineers to accelerate development — a reflection of Japan's desperate scramble to close the widening technology gap with the Allies.

Despite these efforts, Japanese Army radar consistently lagged behind Allied systems in performance and production volume, hampered by interservice rivalry (the Army and Navy maintained completely separate and duplicative radar programs), chronic shortages of critical components like high-quality vacuum tubes, and the escalating destruction of Japan's industrial base by American strategic bombing.

The facility also included specialized testing infrastructure: aerial photographs from 1944 reveal rectangular and circular pools used for testing amphibious vehicles and waterproof equipment, traces of which persisted in local place names — a bus stop near the former Third Research Institute was long known as "Pūru Mae" (Pool Front).

Following Japan's surrender in August 1945, the vast military campus was demilitarized and repurposed. Tokyo Second Normal School (later Tokyo Gakugei University) relocated from Ikebukuro to the former Eighth and Third Research Institute sites in 1946, initially using surviving military buildings as classrooms. Tokyo Salesio Gakuen (a Catholic school run by the Salesian order) established itself on the former Seventh Research Institute grounds in 1947. The communications research facilities of the Fifth Research Institute evolved through several postwar incarnations — from the Radio Research Laboratory to the Communications Research Laboratory — and ultimately became the National Institute of Information and Communications Technology (NICT, 情報通信研究機構), Japan's premier telecommunications research body, which maintains its headquarters at Nukui-Kitamachi 4-2-1, Koganei to this day. The site once dedicated to developing wartime radar now houses NICT's cutting-edge research in quantum communications, cybersecurity, and Japan's standard time system.

Today, virtually no wartime structures survive. The most tangible relic is a granite boundary stone (陸軍境界石杭) inscribed with the characters "陸軍" (Army), standing partially exposed at Honcho 5-31 in Koganei — only about 20 cm of the original 100 cm stone protrudes above ground level. In March 2019, the Koganei City Education Committee installed an explanatory sign beside it. A specimen boundary stone is also preserved at the Koganei Cultural Properties Center. The transformation of this once-secretive military research campus into a landscape of universities, parks, and civilian research institutions stands as a quiet but telling example of Japan's postwar metamorphosis.