Type 89 Chi-Ro Medium Tank
Built by Mitsubishi from 1932 to 1942 and used during the Second World War.

After the first Japanese tank was developed, the Type 87 Chi-I it was found to be too heavy and too slow. So, a light tank at 10 tons weight was designed. The development period was relatively short, due to the designers' experiences with the earlier model. Designers used Steel plate armour developed by the Nihonseikosho Company. The armour was referred to as 'Niseko steel', abbreviated as Nihonseikosho.

The design was relatively conventional having been influenced by the British Vickers Mark C tank that had been purchased by Japan in 1927. The new tank was relatively conventional in design with riveted armour and a forward-mounted turret carrying the main armament, a Type 90 57 mm gun and Type 91 6.5mm machine gun.

The development of the diesel engine was ordered to Mitsubishi Jukogyo Company.After efforts in two and a half years, Mitsubishi had accomplished the development of diesel engine. It was an air-cooling 120 hp diesel engine Mitsubishi A6120VD. It was loaded in the Type 89 Medium Tank from the 1934 production. It was also used by the early production Type 95 Light Tank. This engine was reliable and easy to maintain.

In April 1929, the new light tank was finished. Its weight was 9.8 tons. It was designated the "Type 89 Light Tank." Later, it was re-classified as a "Medium Tank" because the weight increased to over 10 tons due to several improvements. The production of Type 89 Tank started in 1931 and it became the main tank of the Imperial Japanese Army.

The Chi-Ro was first tank that was mass-produced in Japan. The early model, "Ko," had a gas engine and mounted a machine gun on the right side of the hull and the late model "Otsu" had an air cooled diesel 120 PS/1800 rpm engine and mounted a machine gun on the left side of the hull. The diesel engine had several advantages, notably reduced vulnerability to fire and better fuel economy.