Today, we have another wonderful guest article from Soukoudragon (US forums) about Japanese tanks. This time, it’s about something pretty exotic: hightier Japanese light tanks. Author: Soukoudragon Japanese High Tier Light Tanks Possible? What are these STA light tanks? The Type 61 tank was Japan’s first post-war tank. There were four prototypes to this tank. They were the ST-A1, ST-A2, ST-A3, and ST-A4. They all weighed about 35 tons. Well, the A1 and the A2 were about 34 tons. The STA light tanks are none of the above. What are being called the STA light tanks were the plans for Japan’s new post-war tank before the ST-A1 and ST-A2 designs that were accepted and built. The early plans called for the new tank to be light in weight. Historical Background for the Light Weight Plans During the Korean War, American tanks that were over 30 tons such as the M26 and M46 had difficulty in the mountainous regions and rice paddies in the Korean Peninsula whereas the Soviet-made T-34-85 of the North Koreans was able to maneuver in this environment. The terrain in Japan is very similar to the terrain in the Korean peninsula. This is why Japan decided against purchasing the heavier Patton medium tanks from the USA. The Japanese liked the M24 Chaffee since it was light and was able to move around but they needed more firepower. One other reason why a light tank was desired was because of the French thought on tanks at the time. With the advance of HEAT munitions and the development of SS-10 anti-tank missile, heavy armor was becoming to seem like it’s time had passed. For these reasons, at the end of January in 1955, the Ground Staff Office (GSO) submitted the goals for the new 25ton Japanese tank plan which was as follows. Weight: 25 tons Main armament: 90mm Emphasis on a strong engine and low ground pressure Best possible armor within the above requirements. -Before this 25 ton, the plan for the tank was 20 tons with a 76 mm gun, but this changed because of the M-24 could not penetrate the T-34 during the Korean War, thus leading to the need for a 90 mm gun- (Daigensui) There were other ideas for a new tank already around. According to the Chief engineer from GSO of the STA project (Kondo Kiyohide), in September 1953, plans were to have a tank that can perform infantry support as well as play the armored force role. It would need to be able to run along the edges of waterlines, through beach sand, and pass through rice paddies with ease. From the beginning, it was decided to sacrifice armor. It would make up for the lack of armor by using the terrain to its advantage in off-road areas, low vehicle height, good gun depression, and emphasis on torque instead of high speed. It was also to be easily transportable on rail lines. STA Tank Project Development Begins Development started in June 1955 under the Defense Agency order #12. Kondo describes the order as the following. In Showa year 30 (1955) first 2 prototypes are to be built and then increased to 5 prototypes by the end of the year. Contracted companies are Mitsubishi Heavy Industries and Japan Steel Works. Upon reflection on progress thus far, in May 1955, GSO put together a new list of primary requirements as a 30 ton plan which are as follows. -The change from 25 tons to 30 tons is due to the premise that with the development of bazookas and anti-tank missiles 25 tons would not be able to accommodate enough armor- (Daigensui) Crew: 4 Full weight: Under 30 tons Length: about 6.0m Height: under 2.8m Width: about 2.0m Ground clearance: 0.40m Main armament: 90mm Gun depression: -15 Rounds: 50 Secondary weapon: 7.62 MGx1 Engine type: Diesel air-cooled Horse Power: 600hp Horse Power per ton: 20hp/ton Top speed: 50km/h Wading depth: over 1.2m Drive type: Rear wheel drive desired Steering type: Hydraulic desired Ground pressure: 0.8kg/cm2 Rangefinder: Yes Infrared vision: Yes Kondo and the Technical Research Department (TRD) believed that these specs were wish-full thinking. So a development council was held between several organizations. They included TRD, GSO, Defense Agency Bureau Weapons Division, and the Procurement Head Office. Former Lieutenant General Hara Tomio and other experienced tank developers and tank users also participated in the development council. In addition to the development council, TRD consulted with Japan Weapons Industry Group (JWIG). This consultation was open to joining the makers together and also wartime experienced military men. From that meeting with JWIG, a compromise plan was made. It called for two tank designs. A 20~25 ton tank armed with a 76mm cannon and a 25~30 ton tank armed with a 90mm cannon. It was analogous to the concept Germany had in having a Panzer III (37mm) and a Panzer IV (75mm) to complement each other. The 20-25 ton tank reflected GSO’s plan to have a light tank that can easily traverse the terrain of Japan and be easy to transport. And the 25~30 ton tank reflected Kondo and TRD’s plan for firepower and some armor (somewhat contrary to the 1953 description regarding armor). However according to Kondo, some internal ministers have leaked their intention to give a 30 ton tank design a chance in performing the kind scouting that the M24 Chaffee was capable of doing. According to Sone Masanori in 1980, the people that were deeply rooted in the 25 ton concept still felt that it should have been a 25 ton tank made instead. In 1964, at an investigation on the situation of European tank development, Kaihara stated that the 36 ton Type 61 destroyed the vision for a 25 ton tank. In 1954, the same year when GSO gave its 25 ton tank plan, Japan entered into the U.S. and Japan Mutual Defense Assistance Agreement. This meant that there would be technology transfers from the US to Japan including a loan of the 90mm mounted M36 Jackson. If a Sherman based tank was to mount the 90mm cannon, in order for the vehicle to handle the weapon, the weight would need to rise to about 31 tons. This fact made most in the Japanese Ground Self Defense Force (JGSDF) feel that a 25 ton design was unlikely. Leading up to the mock-ups and two Experimental ST-A tanks In the mist of the 25 ton clash, in August 1955, Kondo transferred from the GSO to the TRD and assumed head position of the STA program. This marks the end of the 25 ton plan as well as the compromise plan of the 20~25 ton and 25~30 ton Continue reading →

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