Type 89 I-Go medium tank

(試製1号戦車), 1927 (Imperial year 2587) The Type 89 evolved from Japan's first domestic tank project initiated by the Imperial Japanese Army’s Osaka Technical Arsenal in 1925. The original plan was for two types of tanks to be created: a 10-ton light tank based on the French Renault FT tank, and a 20-ton design modeled after the Vickers medium tank. "Experimental tank No.1" a/k/a Type 87 Chi-I was completed by February 1927 and ready for field trials. However, it was 20-ton and under-powered. The weight of the initial prototype and its low speed did not impress the Imperial Japanese Army General Staff Office, and a new requirement was issued for a lighter tank, with a nominal 10-ton weight. The new design was modeled after the Vickers Medium C which had been bought by the Japanese Army in March 1927. By April 1928, the new "light tank" design was finished. "Experimental tank No.2" was completed in 1929 and designated as the Type 89. Later, the Type 89 was re-classified as a "medium tank" because the weight increased to over 10 tons due to improvements. As the army's Sagami Arsenal lacked the capacity for mass production, a contract was awarded to Mitsubishi Heavy Industries, which built a new tank factory to specifically produce this model. Production of the Type 89 began in 1931 and it soon became the main battle tank of the Japanese Army. Although the Type 89 was well regarded by the army, there were several small problems to be rectified, notably a gap under the mantlet on early models that allowed rifle fire to enter the turret. Work continued on improving the Type 89 after the production started, and as a result variants were developed. ==Design==

The Type 89 required a crew of four (commander/gunner, loader, driver and hull gunner). The design of the Type 89 was relatively conventional with a forward-mounted gun turret carrying the main armament, a Type 90 57 mm gun that was complemented by two Type 91 6.5 mm machine guns. One was located in the front hull and the other placed in a turret ball mount pointed towards the rear, a practice followed with most Japanese tanks. The Type 90 57 mm tank gun had a barrel length of (L14.9), an angle of fire of −15 to +20 degrees in elevation and 20 degrees in azimuth, and a muzzle velocity of , and could penetrate of 20 mm of armor at 500 m (0.8 in/550 yd). During the later stages of World War II, HEAT shells were developed to provide greater penetration of enemy armor. Rather than using soft iron armor, as on the earlier Chi-I, the designers chose to use steel plate armor developed by the Nihon Seikosho Company (JSW). The type of armor was referred to as 'Niseko steel', an abbreviation of "Nihonseikosho". The Type 89 was driven through the rear drive sprocket and featured nine bogies, mounted in pairs on each side, with the forward bogie on an independent suspension. Five smaller return wheels were mounted along a steel girder. The Type A could only communicate with signal flags. Some vehicles were provided with two searchlights for night operations. Later the Type 94 Mk 4 Hei (1934 model) radio communication device with range of and weight of , linked with a radio antenna of in a reverse L shape was installed. ==Variants==

• - The initial production model had a water-cooled 6-cylinder gasoline engine and mounted a machine gun on the right side of the hull. This design could attain only 15.5 km/h, and was also limited by the severe winter climate in northern China. A total of 113 tanks were produced. • - The Ko was superseded in production from 1934 by the model Otsu with an air-cooled Mitsubishi A6120VD diesel engine. The improved model had a new "asymmetric shaped" gun turret complete with a cupola for the commander, and with the machine gun relocated to the left side of the hull. The multiple armor plates of the front hull were replaced by a single shallow-sloped frontal armor plate which provided more protection for the driver. However, the major difference between the versions was the Mitsubishi air-cooled 6-cylinder diesel engine, which had several advantages: lower vulnerability to fire than a gasoline engine, better fuel economy, and greater torque at lower revolutions. A diesel engine was also preferred by the Japanese Army because more diesel fuel than gasoline could be produced per barrel of oil. A total of 291 Otsu tanks were produced. The Type 89B Otsu version was the first mass-produced tank with a diesel engine. ==Combat history==

, January 1942. The Type 89 served with Japanese infantry divisions and first saw combat use during the First Battle of Shanghai in 1932. The short-barreled 57 mm gun was effective at destroying machine gun nests and its armor, although thin, was enough to stop small arms fire. The relatively low speed of was not an issue in these types of operations. During the early stages of the First Indochina War, France set up an ad hoc unit of French and Japanese armour called the Commando Blindé du Cambodge from tanks left over from the Japanese invasion of French Indochina. This unit included one Type 89B tank. ==World War II Japanese units equipped with the Type 89 Tank==

• 1st Independent Mixed Brigade • 3rd Tank Regiment • 4th Tank Regiment • 7th Tank Regiment • 2nd Independent Tank Company • 1st Special Tank Company • 1st Tank Battalion • 2nd Tank Battalion • 5th Tank Battalion • Special Tank Company of China Detachment Tank Unit • 7th Tank Regiment • 8th Independent Tank Company • 9th Independent Tank Company • 2nd Tank Division • Shanghai SNLF Tank Company • SNLF Tank School at Tateyama IJN Ordnance ==Survivors==

in Tiaong, Quezon Province, Philippines. • The Ordnance Training Support Facility, Ft. Lee, VA, US. • The Japanese Ground Self-Defense Force base at Tsuchiura, Ibaraki, Japan. Restored to running condition. • Sinbudai Old Weapon Museum, Camp Asaka, Japan • Villa Escudero, Tiaong, Quezon Province, Philippines • Kieta Memorial Park, Kieta, Bougainville Island, Papua New Guinea • Two tanks west of Ruri Bay, Bougainville Island, Papua New Guinea • Indonesian Army Tank School, Padalarang, West Java, Indonesia • Two turrets in the Malaysian Army Museum, Port Dickson, Malaysia ==See also==