In the 1930s, the Imperial Japanese Army (IJA) introduced the Type 97 Chi-Ha series of medium-class infantry support tanks to which approximately 1,160 examples were produced. The 15-ton vehicle featured thin running tracks along each hull side, a crew of four in a compact hull design with fixed superstructure and a small traversing turret offset to the right side of the hull roof. Armament included 1 x 57mm Type 96 low-velocity main gun and 2 x 7.7mm Type 97 machine guns while armor protection ranged from 8mm to 26mm in thickness. Service entry occurred in 1938.
After its exploits in east Asia, the Type 97 Medium Tank naturally began to show its limitations, especially when compared to developments appearing in Britain, the United States, Germany and the Soviet Union. By 1941, the 57mm armament was severely limited in its battlefield reach and penetration value while the vehicle's thin armor protection made it highly susceptible to well-armed foes - primarily mobile anti-tank teams. Additionally, the Type 97, along with other early-war designs elsewhere, was originally conceived of as an infantry support measure, meant to work in conjunction with infantry forces and not explicitly tackle enemy armor head-on. As such, a direct-combat tank design was now in order, particularly to counter the growing use of Allied armor in the Pacific Theater.
This naturally spurred development of a new and improved medium class tank type along the same functional lines of the Type 97. The Type 1 "Chi-He" proved of relatively similar scope and function though more modern than her predecessor. A 47mm Type 1 high-velocity main gun was selected and mounted to a centrally-located turret along a fixed hull superstructure roof. Power was supplied by 1 x Mitsubishi Type 100 air-cooled V12 diesel-fueled engine of 240 horsepower output which provided for road speeds of up to 27 miles per hour and an operational range of 130 miles. The hull was suspended across a bell crank system for acceptable cross-country support which was required of the mountainous jungle terrain to be encountered. Defense was through 2 x 7.7mm Type 96 machine guns - one fitted coaxially in the turret and the other in the front left hull (the driver seated front-right). Crew accommodations were increased to five personnel while armor protection ranged from 8mm to 50mm and overall weight was in the vicinity of 17 tons. Communications was managed through an included radio suite - the Type 1 becoming the first Japanese tank to feature wireless (previous communications were accomplished through visual signal flagging). The running gear included thin track sections, four road wheels to a hull side, a front-mounted drive sprocket, two track return rollers and a rear-mounted track idler. The engine was fitted to a compartment at the rear of the hull. Overall, the Type 1 was a heavier design with improved armor protection and a more potent main gun armament than the Type 97 before it.
Design work on the Type 1 began in 1940 to which the requisite period of trials ensued prior to adoption by the IJA. The first vehicles appeared in 1941 and serial production (delayed by lack of resources) spanned from 1943 to 1944 to which manufacture was limited to just 170 vehicles. With that, the Type 1 was restricted in number and utilized in defense of the Japanese homeland in anticipation of the Allied invasion of Japan proper (the Japanese initiative was wholly lost by this point in the war and defensive-minded approaches to war were in order). Sources indicate that the Type 1 may have been fielded in limited numbers during the Battle of Leyte in the waning stages of the Philippines campaign but these would not have fared any better than other Japanese light and medium tanks against the AmericanM4 Sherman - the IJA's principle armored foe in the Pacific. Despite the Type 1's modern approach, the M4 still outmatched the design in every category - it was heavier, well-armed and well-armored and evolving with every given month in the war thanks to combat experiences in Europe. The Japanese military - while having promoting an excellent navy and strong air force during the war - never managed to field any truly successful tank designs for its army in World War 2 and the Type 1 seemingly continued this trend. Additionally, "medium" tanks (as classified by the IJA) were more akin to "light" tanks elsewhere else, which immediately placed them at something of a tactical disadvantage on the modern battlefield.
Nevertheless, the promising nature of the Type 1 allowed experimentation with the existing design as a self-propelled anti-aircraft gun system in the Type 1 "Ta-Ha". However, only a single prototype of the system was completed (aptly armed with 2 x 37mm autocannons for the role). The system could have presumably been fielded as an anti-tank/anti-personnel system as well.