Top-secret plans, tests of Japanese army’s planned ‘Oi’ super tank discovered


An illustration of a scale replica of a 150-ton super-heavy tank that the Imperial Japanese Army was secretly developing during World War II. According to a blueprint, it would have measured 10.1 meters in length and 3.6 meters in height. (Provided by Kunihiro Suzuki)

An illustration of a scale replica of a 150-ton super-heavy tank that the Imperial Japanese Army was secretly developing during World War II. According to a blueprint, it would have measured 10.1 meters in length and 3.6 meters in height. (Provided by Kunihiro Suzuki)

October 24, 2015

By YASUJI NAGAI/ Senior Staff Writer

Secret blueprints and other documents detailing the production of a massive 150-ton multi-turreted tank that the Japanese military was constructing during World War II but never completed have been found on the used book market.

Kunihiro Suzuki, 57, president of Fine Molds Corp., based in Toyohashi, Aichi Prefecture, obtained the trove of designs, specifications, reports on field tests and work diaries.

The plastic model maker is now creating a scale replica of the phantom tank, which will go on sale in December.

According to six volumes of a work diary kept during the process, the behemoth never made it out of the prototype stage due to a shortage of steel plates as the war took a turn for the worse.

“The documents show how the military ignored the supply and manufacturing departments,” said Suzuki, who is well-versed in military vehicle. “I hope the scale replica I am making will help people think of the recklessness of the military.”

The Imperial Japanese Army placed the order for a super-heavy tank with Mitsubishi Heavy Industries Ltd. in April 1941. The first experimental runs of the prototype were held in April 1942.

The shape of the tank and other details had not been known until the discovery of the documents, except that the tank was code-named “Mito” by the heavy machine manufacturer and “Oi” by the army.

According to the plans, Mito was to scale 10.1 meters in length, 4.8 meters in width and 3.6 meters in height and weigh 150 tons. It would have dwarfed Nazi Germany’s formidable 69-ton Tiger II (King Tiger) heavy tank.

The Mito tank was to be outfitted with a main cannon turret and two other gun turrets, with one of the smaller turrets in the rear.

Mitsubishi Heavy Industries was initially directed to complete the vehicle in three months, by the end of July 1941. However, due to technical problems including malfunctioning of the cooling system and shortage of materials, the test run was delayed until nine months later.

While an order was placed with Mitsubishi Heavy Industries to manufacture the gun turrets in May 1942, steel plating with a thickness of 30 millimeters or 35 mm that were required for them were not available. So the company had to temporarily disassemble the prototype.

Describing efforts to obtain the steel plates, an entry in the diary dated July 28, 1942, notes that the procurement department was suffering from “a shortage of materials even for (front-line) maintenance vehicles” and “there is no solution for this for now.”

In June 1943, the prototype was transported from Mitsubishi’s Tokyo plant to the Imperial Japanese Army’s Sagami Army Arsenal and reassembled.

With the worsening of the war situation, development of the turrets was forced to be suspended and the vehicle was secretly disassembled.

The six diaries, classified as “top secret” and “military secret,” also reveal that only authorized employees could enter the Mito manufacturing site, and those who entered were required to wear special armbands.

By YASUJI NAGAI/ Senior Staff Write

About Uy Do

Banking System Analyst, former NTT data Global Marketing Dept Senior Analyst, Banking System Risk Specialist, HR Specialist
This entry was posted in Japan, Tanks, Weapons and tagged . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s