The Type 89 Yi-Go or Chi-Ro medium tank was the most important Japanese medium tank of the 1930s, and was the first at least partly Japanese-designed tank to be accepted by the Imperial Japanese Army. Development of the Type 89 began in 1927 after Japan received an early example of the Vickers Model C. The Osaka Army Arsenal (Osaka Rikugun Zoheisho) was responsible for both the development of the new medium tank and the evaluation of the Vickers Model C. Their first design, for a 9.8 ton Number 2 medium tank, later knock as the Type 2587 was rejected because of its thin armour and limited firepower, but a second design of 1929 was accepted as the Type 89A Yi/I-Go (first tank) or Chi-ro (medium second, applied retrospectively) .
This new tank was a modified version of the Vickers Model C. The hull was virtually identical, although the glacis was modified. The complex Vickers version replaced by a simple two part glacis plate. This had a perpendicular section at the top, running from the top of the hull to the fender line, containing the driver’s visor and hull machine gun. From the fender line to the level of the front axis the glacis sloped outwards, producing a slight “beak”. An entry hatch was placed below the machine gun in the lower glacis plate. Like the Vickers original the Type 89A was constructed with a mix of welded and riveted plates.
A new main turret was developed for the Type 89A Chi-Ro. This was a slightly conical symmetrical curved sided turret, with the 57mm main gun at the front and a ball mounted 6.6mm machine gun at the rear. Early versions of the Type 89A featured a “top-hat” cupola on the right of the turret. Very early examples of the tank were armed with a Type 11 37mm cannon, but the majority used the Type 90 57mm cannon.
The Type 89A was given nine small road wheels, eight carried by two four-wheeled bogies with equalizer suspension, and one independent wheel. The engine and drive wheels were both at the rear of the tank.
The Chi-Ro grew in weight throughout its production run. The original 1939 version weighed just less than 10 tons. By the time it entered production that had risen to nearly 13 tons, and by the time production ended the tank weighed 14 tons.
Production began in 1931, partly at the Sagami Arsenal and partly at Mitsubishi. Most sources indicate that 113 Type 89As and 291 Type 89Bs were produced between 1931 and 1939, with production of both models peaking in 1932-34. The slow start to production meant that the first Type 89s were used alongside a small number of imported Renault NC tanks, but the imported tanks were soon phased out.
The design of the Type 89 was repeatedly modified during its long production run. The first set of changes came in 1932, with the introduction of the Type 89B or 89 Otsu (second), also sometimes known as the Type 2592 Chi-Ro. The Type 89B had a modified straight glacis, which ran diagonally from the hull roof to the front axle. The rounded turret was replaced with an asymmetrical hexagonal turret, with the machine gun offset to one side, in what would become the standard layout for Japanese tank turrets. The “top-hat” cupola was replaced with a more practical “mushroom” cupola, with a two-part hatch on top (the older cupola had doubled as a hatch lid).
After the fighting in Manchuria in 1942 the petrol engine of the Type 89 Otsu was replaced by a diesel engine, making it the first mass produced diesel powered tank in the world.
A second set of major changes came in 1936. The track links were given enlarged claws to improve their grip in rough terrain, and the number of return rollers was reduced to four. The driver’s and machine gunner’s positions were reversed, with the driver on the right and the machine gunner on the left. Ditching gear was added to the rear of the tank. This version was sometimes designated at the Type 2594 Chi-ro. A final major change came in 1937 when the Type 90 cannon was replaced by a Type 97 57mm cannon, firing high explosive shells.
The Type 89 Chi-Ro took part in the fighting in China. Small numbers were present during the Shanghai incident of 1932, and the type became increasingly important as the war continued. They were also involved in the early fighting in Manchuria.
By the end of the 1930s the Chi-Ro was approaching obsolescence, but it was still effective in China, where the limited number of Chinese tanks and anti-tank weapons and the large scale of the battlefield compared to the number of tanks involved meant it was still a useful weapon. 78 Type 89s, along with 41 Type 94 tankettes took part in the advance into China after the Marco Polo Bridge incident.
The Japanese tanks were less successful during the Lake Khasan and Halka River/ Khalkin-Gol/ Nomonham incidents of 1939. The thing armour of the Type 89 was exposed against the 45mm tank and anti-tank guns used by the Soviet forces during the fighting (although only 13 of 42 Japanese tanks acknowledged to have been damaged were actually written off).
The Type 89A Chi-ro was used in small numbers during the Japanese invasion of the Philippines in 1941-42. A number were still in use with the 7th Independent Tank Company in October 1944 when the Americans returned to the islands. These tanks were destroyed in October 1944 during a failed Japanese counterattack early in the fighting on Leyte.
Names (see article on Japanese tank designations)
2589 Type 89A Chi-ro (medium second)/ Shu Sensha Gata 89 Kai Chi-ro (retrospectively applied)
Type 89 Yi-go/ I-go (first model) (original name)
Type 89B Oksu
Number produced: 404
Weight: 11.8 tons (early) 14 tons (late 89B)
Engine – Type 89A: 118hp gasoline engine
Engine – Type 89B Otsu: 120hp Mitsubishi diesel engine
Max Speed: 15mph/ 24km/hr
Max Range: 200km (89B)
Armament: 57mm main gun, turret mounted 6.5mm machine gun, forward firing hull 6.5mm machine gun