In order to keep themselves technically abreast of the most advanced foreign designs, the Japanese had purchased from abroad some contemporary tanks including samples of the Vickers Mark C and Vickers-Armstrongs Six-Ton tanks as well as a few Vickers Carden-Loyd Mark VIB tankettes. The French Renault concern was awarded a production contract for a few dozen of an offspring of their wartime FT light tank — the 8-ton NC tank which became designated as the 'OTSIT or 'B', in the Japanese Army.
From the Vickers C tank the Osaka Arsenal derived an 8-ton, four-man light tank pilot model armed with a 57mm gun. The promise evinced by this machine resulted, in 1929, in the Mitsubishi Heavy Industries Company receiving an order for the development of a projected design, the 'I-GO' the prototype of which was completed in 1931. The 'I-GO' was adopted as the Type 89 medium tank, a 12-ton vehicle armed with a 57mm gun and capable of a speed of 25kph. The Type 89 was placed in production during 1931 just in time to be involved, together with some OTSU (Renault NCI) tanks, in the 'incident' which occurred at Shanghai in 1932 as a result of Japan's aggressive policy towards China. The petrol-engined Type 89 was retained in production until 1936.
The year 1933 was an important date in the history of Japanese tank development. During this year Major (later Lieutenant-General) Tomio Hara designed his bellcrank 'scissor' type suspension (resisted by horizontal or sloped coil springs) which was to become widely used on subsequent Japanese tanks, from the Type 94 tankette up to the Type 5 CHI-RI medium tank, the last Japanese prototype of World War II. In 1932, Mitsubishi Heavy Industries had produced an air-cooled diesel engine suitable for installation in tanks, and in 1933 this engine was experimentally fitted in a Type 89 medium tank. This initiated a large scale tank 'dieselisation' policy in Japan. After trials under extreme climatic conditions, this diesel power plant was standardised for driving the subsequent Type 89 medium tank production models which became designated as the Type 89-OTSU (Type 89-B). The earlier gasoline version was then redesignated Type 89-KO (Type 89-A).
In the early thirties, the Japanese considered a limited mechanisation policy. At first, studies were concentrated on wheeled armoured cars, but terrain conditions in the Far East favoured tracked machines and such a vehicle was finally preferred. The design was undertaken by Ishikawajima and resulted in the machine-gun armed Type 92 combat car, for which a welded construction was employed.
The development of a line of small vehicles classified as tankettes ('MAME SENSHA' in the Japanese nomenclature) had also started around 1932, when the Imperial Army began to evince interest in an armed and armoured tractor able to tow a tracked trailer carrying supplies and ammunition up to forward positions of the front line. The first Japanese tankette, known as the Type 94 (1934), constituted an entirely original type of construction although certain details of design may be traced to foreign types. Further development of the basic design led, from 1936 onwards, to a modification of the original trackwork which was now fitted with a trailing idler. This increased the ground contact length and the vehicle gained in cross-country mobility. Further adaptation of the Type 94 tankette gave rise to a dieselised prototype version which in turn formed the basis for the improved Type 97 TE-KE tankette, a diesel engined 4.5ton midget tank armed with a 37mm gun. After the TE-KE further development of the tankette was abandoned, the Japanese Imperial Staff having begun to appreciate that the entire concept was outdated.
The Japanese tank designation system Japanese tanks were designated by a type number indicating the last two digits of the year in the Japanese calendar in which production was initiated. The year was taken from the legendary foundation of the Japanese Empire — 660BC western terms — which was their year 0. The European equivalent of a Japanese year is thus found by subtracting 660. Thus a tank labelled Type 95 (the last two digits of 2595) was a model of the year 1935 in western chronology. From 2601 onwards, the last digit of the Japanese year was used, i.e. Type I (1941), Type 2 (1942) and so on. In some cases the type number was followed by a word descriptive of its function classification and a code letter given by the manufacturer; thus:
Type 97 CHI-HA was Model 1937, Medium 'C.
Type 94 TK was Model 1934, Tankette.
Type 98 KE-NI was Model 1938, Light 'D'.