Based on battlefield information from the Eastern Front, Department of Army Weaponry published a report demanding a shift of tank design focus from Infantry tank to tanks specialised for anti-tank missions. The Army's requirements for the new medium tanks were an increase of weight from 20 tonnes to 35 tonnes and an armour upgrade from 50 mm to 75 mm. The new tank would be mounted with a new 75 mm gun instead of the previous 57 mmanti-tank gun. Production focus would also prioritise quality over quantity. The new medium tank was designated as Type 5 Medium Tank Chi-Ri. A single unarmed prototype of the Type 5 Chi-Ri was completed by May 1945. The project was abruptly abandoned to free up manpower and critical resources to concentrate on the development and production of the more practical Type 4 Chi-To medium tank. As with many innovative weapons projects launched by Japan in the final years of World War II, production could not advance beyond either small numbers or the prototype stage due to material shortages, and the loss of Japan's industrial infrastructure to the Allied bombing of Japan. It was the last tank "developed" by the Imperial Japanese Army.
Design
The Type 5 Chi-Ri featured a lengthened version of the Type 4 Chi-To chassis, with eight road wheels per side instead of the seven of the Chi-To. It had the usual Japanese track arrangement with forward mounted drive sprockets and rear mounted idlers. The Type 5 Chi-Ri had sloped welded armor, with a maximum thickness of 75 mm at the front hull; 25–50 mm on the side; 50 mm on the rear and 50 mm on the turret. The Type 5 Chi-Ri was initially to be powered by a Mitsubishi Diesel engine, but the advancements needed to provide the necessary horsepower fell behind schedule, and an 800 hp V-12 gasoline-fueled aircraft engine designed by BMW in Germany and licensed to Kawasaki Heavy Industries in Japan was selected instead. The "Kawasaki Type 98 800 HP engine Ha-9-IIb" was detuned for the tank to 550 hp. The tank had a hexagonal gun turret and on the left side of the turret roof was a commander's cupola. In front of that was a crew hatch. Originally, the prototype tank was to be fitted with the same Type 5 75 mm tank gun used on the Type 4 Chi-To. A secondary weapon of a fixed front hull-mounted Type 1 37 mm tank gun was fitted in the position normally taken by a machine gun. Alternatively, the design called for using two Type 97 heavy tank machine guns in place of the front hull-mounted Type 1 37 mm tank gun. Accordingly to another source, the design called for a ball mount for a Type 97 machine gun on the left side of the turret for use in close combat situations. There were also plans for a Type 5 Chi-Ri II, to be diesel powered and using the Type 5 75 mm tank gun as its main armament.
The Ho-Ri I was a more powerful tank destroyer using a 105 mm cannon in place of the 75 mm gun design and an additional 37 mm gun in the front armored plate. The armor was to be 30 mm thick and it was to have a crew of six. It used the Type 5 Chi-Ri tank chassis. The superstructure for the main gun was placed at the rear, the engine was positioned in the center area of the chassis and the driver's station was in the front hull section; all similar in design to the German Ferdinand/Elefant heavy tank destroyer. According to "The National Institute for Defense Studies, Ministry of Defense, Military Administration of Munitions Mobilization, Production Chart of January to April of 1945", the plan was to produce a total of 5 Ho-Ri gun tanks by March 1945. However, no prototypes are known to have been completed. Another variant of the Ho-Ri was to have a twin 25 mm anti-aircraft gun on top of the rear casemate superstructure in a "swivel mount". A second version planned was the Ho-Ri II heavy tank destroyer. It was to use the Type 5 Chi-Ri tank chassis. The boxy superstructure for the main gun was completely integral with the hull's sides and placed at the center of the chassis. The engine compartment was moved in the rear area of the chassis. It also was to use a 105 mm cannon as its main armament.
