While the Imperial Japanese Army enjoyed a tremendous period of success through the opening phases of the war across Asia and in the Pacific, its armored formations were beginning meet their match on the ever-evolving battlefields that was World War 2. The Americans began fielding their war-winning design - the M4 Sherman Medium Tank - in astronomical numbers along all fronts and through their major Allies, making it an omnipresent foe. While Allied technology and doctrine moved ahead to develop and produce ever-more powerful instruments of war, there simply was not the level of advancement for the IJA in keeping pace with their adversaries.
As such, Japan was still fielding a growing list of light and medium tanks that, by war's end, were becoming wholly outclassed against Allied anti-tank weapons. Many were finished with relatively thin armor protection and small caliber main guns that immediately placed them at severe disadvantages when facing off against M4 Shermans and the like. While the IJAs tanks could still serve battlefield purposes - particularly as armored infantry fighting vehicles - their tactical value against Allied medium tanks and anti-tank weapons was inherently weak. In the later stages of the war, a late initiative began to yield some hope for the IJA - but these endeavors simply arrived too late to be of much use in a battlefield sense for Japan formally surrendered to the Allies in August of 1945 (after succumbing to two Atomic bombs no less) and the war was officially over in September of that year.
The Type 4 ("Chi-To") was one such development that was intended to help level the playing field in favor of the Japanese tanker. She was a medium-class tank system, weighing in at 33 Short Tons and armed with a capable long-barrel Type 5 75mm main gun (based on a proven Japanese anti-aircraft weapon, itself based on an original Swedish Bofors design). Armor protection was 75mm (3 inches) at her thickest facings with construction being of all-weld. The long-running track assemblies straddled the hull which sported a low-set superstructure under the turret. The track systems featured seven small road wheels to a track side with the drive sprocket at the front, the track idler at the rear and three track return rollers. The chassis was fitted atop a Bell crank suspension system and powered by a single Mitsubishi AL Type 4 air-cooled V12 diesel-fueled supercharged engine outputting 412 horsepower at 1,800rpm. This provided the Type 4 with a top speed of 28 miles per hour and an operational range equal to 160 miles. The 75mm main gun was backed by a pair of Type 97 Light Machine Guns for anti-personnel work - one fitted to the bow and the other as a coaxial mount. There were also mountings on the turret roof for adding another machine gun for close-in anti-aircraft defense. The turret itself sported a rather tallish profile - making the tank system, as a whole, promote a rather tall side profile - a sure negative on the battlefield. The turret was completed with slightly angled side surfaces and shaped as a hexagon when viewed in the top profile. The Type 4 tank was crewed by five personnel made up of the driver, tank commander, gun layer, ammunition loader and radio-operator/bow machine gunner - a conventional crew arrangement for the time.
Design of the Type 4 began in 1942 and persisted through the years following. The system was intended to replace the outgoing Type 97 tank series which, itself, held origins as far back as 1936. Needless to say, a battlefield tank with pre-war beginnings was anything but a frontline tool at this late stage in the war. However, disruptions to the Type 4 program inevitably caused it to move at a slow pace for it was not until 1944 that the first completed Type 4 tank was made available.
The slow development cycle and delays in reaching serial production were largely attributed to the Allied air campaign which targeted Japanese industry. As the Empire lost more and more of her holdings in the Pacific Theater, attacks could now be solely concentrated against the Japanese Mainland proper, striking at the heart of her industrial output and disrupting supply lines, production and design initiatives such as the Type 4. To that end, the new medium tank languished for a longer period than anticipated, with nothing more than two fully completed vehicles to show for the final effort. At this point in the war, Type 4s would have certainly been used in defense of the Japanese Mainland from the expected amphibious invasion from the Allies. It is noteworthy that an additional handful of Type 4 tanks were in incomplete stages of construction at the end of the war.
At the time of its development, the Type 4 Medium Tank was one of the most technologically advanced armored mechanized systems. If completed, perhaps earlier in the war, it would have proven something of a formidable system for the M4 Sherman to contend with. However, whatever effect on the war it may have had is now lost to interpretation and speculation.