One of the least applicable adjectives to Japan in the first half of the 20th century would be "peaceful". The Japanese fought a lot of wars, and by the 1930s, their influence in the Far East was great. A significant part of this success could be attributed to the careful attention that the highest military ranks paid to technical novelties in the field of armament. Naturally, the Japanese could not pass up on tanks. Purchases of vehicles began in 1917 and domestic designs reached the battlefield less than a decade after. These were medium and light tanks whose firepower was sufficient against China or island garrisons with no anti-tank armament.
The least studied part of Japanese armoured history is the design of heavy tanks. The data about this class of vehicles is scarce and contradictory, but there is still something that can be said.
The topic of heavy tanks was explored by Japanese engineers long before the war. Work on the first project built in metal, called Type 91 or 2591, began in 1930. The design of this tank relied largely on the experience of building the Chi-I medium tank. The group of engineers working on it included Tomio Hara, who will become the most well known Japanese tank designer.
Type 91 weighed only 18 tons, which was closed to a medium tank by European or Soviet standards. However, due to the tank's 70 mm gun, it was designated a heavy tank. Under the influence of the British armoured school of thought that embraced multi-turreted tanks, the Type 91 carried three turrets placed along the hull. Only one tank was built in metal. Even though it made a good impression on the military, the tank did not enter mass production, as a modernization was requested.
Type 95, the last pre-war heavy, appeared in 1935. The tank's designers made an emphasis on technological simplicity and improvement of armament. For instance, the low velocity 70 mm gun that was only useful for fighting infantry and fortifications was complemented by a high velocity 37 mm gun. It could penetrate 30 mm of armour at 300 meters, making it a dangerous foe for lightly armoured Soviet T-26 and BT tanks.
Compared to the Type 91, the tank weighed in at a hefty 27 tons. Again, it was closer to medium tanks, but the Japanese decided otherwise. They had the right to do so, as the Type 95 had no equals in armament or armour in the Far East. Nevertheless, the reaction of the military was mixed. On one hand, the increased combat capability was good, on the other hand, the increased mass and decreased speed were not. They to limit the tank's production to a small batch, assigned to an arsenal in Osaka. It is not known how many vehicles were finished, but modern historians consider that it was most likely less than 10. Type 95 was largely used for training purposes on Japanese territory. It is known that in 1938 some tanks were sent to China for the final stages of the Sino-Japanese conflict.
If built, the Mi-To would be the height of the Japanese tank industry. As it stands, it is only a mystery. Data on this super-heavy is scarce and contradictory. Only three things are known for sure. One: work began after the Japanese defeat at Khalkin-Gol in 1939. Two: the Mi-To was not just one tank. It was a series of experimental designs that lasted all the way until Japanese surrender in 1945. Three: all superheavy tank designs were multi-turreted.
"Mi-To" was short for "Mitsubishi-Tokyo", the factory that was developing the tank under the strictest veil of secrecy. In military documents it is also encountered under the index "O-I". Engineer Shigeo Otaka, who participated in the development, recalls that his group worked in barracks, in a small room separated from the outside world by a double door. This minimized the chances of anyone accidentally looking into the room and seeing what was happening. Various groups at Mitsubishi worked on different parts of the tank and had no idea what they were designing. Engineers in that "chamber of secrets" were tasked with assembling this mosaic of components.
As mentioned above, several Mi-To projects existed over the years. An evolutionary chain was followed where every link was superior to the previous in armour and armament. As a consequence, each tank grew heavier and heavier. The first Mi-To weighed about 100 tons, the last was 140-150.
Why did Japan need such a beast? At first, before the home islands were in danger, these tanks were designed as assault vehicles. In 1944, the Japanese defense perimeter of Pacific islands was breached. In April of 1945, Iwo Jima fell to the Americans. It was clear that an armada of landing craft could land on Japanese shores at any time. A superheavy tank was now a mobile coastal defense stronghold.
The main armament of the Mi-To series consisted of battleship guns ranging from 100 to 150 mm. These guns were powerful enough to deal significant damage to light landing vessels and the ships protecting them. At the same time, the armour of these superheavy tanks would protect the crew from explosions and shrapnel. Only a direct hit could destroy the tank, and enemy ships would not be able to hit such a small target.
The long history of the Mi-To ended with the end of the war. Was even one prototype finished? According to the book "Imperial Japanese Army Land Weapon Guide", only one was. After assembly, it was taken apart and shipped to Manchuria for field trials, which revealed serious problems with the reliability of the suspension. However, like most information on Japanese superheavy tanks, this data is not 100% confirmed.
Original article available here.