WW2 Japanese Prototypes


Empire of Japan (Mid 1930’s)
Heavy Tank – Prototype/Paper design

After the First World War, most nations started looking at their armed forces, specifically to how advances in weapons technology affected the way they would and could fight. The Japanese were no exception, especially in armored vehicle development. In many respects, the Japanese Army avoided many of the dead ends that other nations experienced and arguably came closer to getting armored warfare right than any other nation. This was quite likely an accident forced upon the Japanese by circumstances.
One of the few dead ends that the Japanese did encounter, however, was the multi-turreted tank, the Mitsu-104, which was most likely a development of the Type 97 Heavy tank, which was the one heavy tank the Japanese had that went into service.
Schematics of the Mitsu 104 Heavy Medium Tank found in the UK National Archives.


All the information on the Mitsu-104 comes from a British military intelligence dossier on enemy tanks, which was compiled between January 1939 and March 1943. This information was then later passed on to the rest of the Commonwealth and the United States, who included it in their own enemy equipment handbooks that were issued to the armed forces.
The British information came from original Japanese documents, obtained before the Second World War, although no details of where or how these documents were obtained is included in the files. The paper type and size are all identical to the Japanese standards used at the time, both of which were different from the conventions used by the British, all of which implies that the documents are original, and thus credible.
There does appear to have been some confusion within the documents about the exact location of weaponry on the tanks though. This is likely because of some inaccuracies in the Japanese text, which again raises the mystery about where the documents came from. Despite this, the translations includes original, archaic Japanese measurements (which are re-created in the specifications table).
The British documents describe the Mitsu-104 as a ‘Heavy Cruiser’, despite the fact that Japanese documents clearly referred to it as a Heavy.

Drawing of the Mitsu 104 from a Swedish intelligence document. Source


Japan spent a large part of the 1920’s obtaining examples of foreign armored vehicles and concepts. One such example is the A1E1 Independent, which the Japanese obtained plans for. This resulted in the Ishi-108. One of the few failures of tank design the Japanese picked up was the idea of multi-turreted tanks. This likely came from their interest in the British A1E1 Independent and the Soviet T-28 tanks.
Multi-turreted tanks are almost universally considered to be a bad idea because they add weight to the tank from items such as gearing and the structure required to mount a turret as well as making the vehicle much harder to command. On a single turret tank, this weight could be used for more armor or bigger guns and engines. Multiple turrets also comprise the armor integrity by having a series of holes in the armor to mount the turrets.

The Mitsu 104 from a 1944 British-issued recognition handbook on Japanese equipment.
This unfortunate trend in design existed in all the Japanese heavy tank projects, apart from the AI-96 from 1936.
One such multi-turreted design was the Mitsubishi 104, which is shortened in the documentation to “Mitsu-104”.
There seems to be no evidence the Mitsu-104 was ever built, unlike the Type 97 Heavy Tank. Design wise, it seems to have been a logical development of the Type 97, looking far more refined and capable, although the exact date of the tank’s design is unknown.
The Mitsu-104 had three slightly conical turrets. The main turret mounted a 75mm low velocity gun possibly based off one of the Japanese field artillery guns of the same calibre. Two sub-turrets were mounted on the front hull, each with a machine gun.

Original Japanese drawings of the Mitsu 104 found in the British National Archives.
There was some confusion about the armament for the tank. A pair of 37mm guns were listed, however, the British were confused as to their location. The Type 97 Heavy tank from 1937 had the option of two 37mm guns or a single 75mm guns mounted in the turret. This is likely because the Japanese considered the heavy tanks for the support of the infantry, and in the Japanese military 37mm guns were called ‘rapid fire infantry guns’. The British documents suggest the Mitsu-104 could have had 37mm guns in the sub-turrets, which certainly look big enough to mount such a weapon. This could, of course, be a translation mistake for the twin guns in the main turret.
The rest of the hull was conventional in its layout with the engine at the rear of the tank. Although the tank is rather wide for its size.
The suspension was the same style of Bell Crank suspension used on most Japanese tanks of the period and indeed lived on until the failed O-I Super Heavy Tank design.

The Mitsu-104 with 37mm main armament.

The Mitsu-104 with 75mm main armament.

Both illustrations are by William ‘Richtor’ Byrd, funded by DeadlyDilemma through our Patreon campaign

United States tank recognition chart showing the Mitsu 104 in the lower left corner.


The design, from the particulars written down, does seem to be over-optimistic in regards to its mobility and speed. This was a common fault with Japanese heavy tank plans, with tanks such as the Ishi-108 and O-I having suspiciously overinflated claims of speed from engines that seem to produce far too little power to propel such masses at such speeds. For example, a 30 ton Sherman tank with a 350hp engine could obtain about 22mph. The Japanese predicted that the same power output would move the 29 ton Mitsu-104 at 30mph. To achieve similar figures, a Sherman needed over 400hp.

3D reconstruction of how the Mitsu 104 might have looked like. Source: Forgotten Tanks and Guns of the 1920s, 1930s and 1940s  by David Lister

The Mitsu 104 being mentioned in the Japanese military forces. Report No. 12-b(11), USSBS Index Section 6.

Mitsu-104 specifications

Designer Mitsubishi
Dimensions (L-W-H) 8.30 x 3.20 x 2.80 m (27.2 x 10.6 x 9.3 ft)
Weight 29 tons (58000 lbs)
Crew 8
Propulsion Water cooled, Mitsubishi 12 Cylinder Petrol engine, delivering 350hp at 2200rpm. Fitted with a 12 volt electrical starter.
Armament A combination of 75mm and 37mm guns, and several machine guns.
Armor 25-30mm (0.98-1.18 in)
Speed 12 Ri (25mph, 40kph)
Gradient 40 degrees
Step 1.20 m (3.11 ft)
Trench Crossing 3.90 meters (12.10 ft)
Fording 1.20 meters (3.11 ft)

WO 208/1320, UK National Archives in Kew, London
Forgotten Tanks and Guns of the 1920s, 1930s and 1940s  by David Lister
World War II United States recognizition chart
British 1944 Japanese-equipment recognition handbook
Japanese military forces. Report No. 12-b(11), USSBS Index Section 6,

Forgotten Tanks and Guns of the 1920s, 1930s and 1940sForgotten Tanks and Guns of the 1920s, 1930s and 1940s

By David Lister

History forgets. Files are lost and mislaid. But this book seeks to shine a light, offering a collection of cutting edge pieces of historical research detailing some of the most fascinating arms and armament projects from the 1920s to the end of the 1940’s, nearly all of which had previously been lost to history.Included here are records from the UK’s MI10 (the forerunner of GCHQ) which tell the story of the mighty Japanese heavy tanks and their service during the Second World War.

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WW2 Japanese Prototypes

Type 97 Chi-Ni

Japan (1938)
Experimental Medium Tank – 1 built

Chi-Ha’s Competition

In 1938, the Japanese military began looking for a replacement for the ageing Type 95 Ha-Go light tank. High ranking members of the military had a preference for more lightly armored infantry support vehicles. As such, two medium tank projects were put forward, with specific guidelines set.

These were: a maximum weight 10 tonne, 20mm maximum armour thickness, 3 man crew, maximum speed 27 km/h (17 mph), trench crossing capability of 2200 mm upgraded to 2400mm with a ditching tail and armament consisting of a 57 mm gun and one machine gun.


Under the working name of Medium Tank Project Plan 2, The Type 97 Chi-Ni (試製中戦車 チニ Shisei-chū-sensha chini) was submitted by Osaka Army Arsenal. It was a low cost alternative to its competition, the Type 97 Chi-Ha, made by Mitsubishi Heavy Industries.

The Chi-Ni was envisioned as a smaller, lighter alternative to the Chi-Ha, and was easier and cheaper to produce. The prototype was completed early 1937, taking part in trials against the Chi-Ha soon after.

It featured a number of cost-cutting features. It was of mostly welded construction, Its drive wheels, idler wheels and tracks were the same as those used on the Type 95 Ha-Go. For a time it was tested with the Ha-Go’s suspension, but it was soon apparent that it did not support the longer chassis well enough.

A mock-up of the Chi-Ni hull alongside the Ha-Go. Source: The Koku-Fan, Oct. 1968



The hull was designed with a streamlined silhouette to protect from shell damage, and was of a monocoque design. Also known as structural skin, monocoque is a French word meaning “single hull” and is a structural system where loads are supported through an object’s outer layers.

A side shot of the Chi-Ni prototype. Source:

This method is also used on some early aircraft and in boat building. Because of this, the tank was mainly of a welded construction, an unusual design choice for Japanese tanks of the era, which were mostly riveted onto a skeletal framework. The rear of the hull also featured the somewhat archaic feature of a ditching or “tadpole tail” to help it cross trenches. This was a removable feature.

Though the armor was only 20mm thick, it was extremely well-angled. The driver’s position was encased in a semi-hexagonal box; in front of this was the flat bow, leading to a negatively angled lower glacis.

A rear view of the Chi-Ni, showing the removable ditching tail..


The main armament consisted of the Type 97 57mm. Its primary ammunition was HE (High-Explosive) shells and HEAT (High-Explosive Anti-Tank) rounds. This was the same gun as found on the initial models of the Chi-Ha. The gun kept the Japanese tradition of excellent depression. In the Chi-Ni’s case, this was negative 15 degrees over the front and left side. Depression over the right and engine deck would have have been slightly limited by at least 5 degrees.

The depression suited the tank’s infantry support role because it was able to fire High Explosive shells at close range on advancing enemy infantry, or down into occupied trenches. Furthermore, like the Chi-Ha, the Chi-Ni’s turret ring was made as large as possible, to allow for any future turret upgrades.


The tank shared a similar bell crank suspension to the Ha-Go – this being a near constant of Japanese tank designs of the epoch. The difference was that in the case of the Chi-Ni, at the end of each bogie were 2 small road wheels, making 8 per side.

The forward-mounted drive wheels were powered by a Mitsubishi 135 hp diesel engine that would propel the vehicle to a blistering 27 km/h (17 mph). It was also tested with the 120 hp Mitsubishi A6120VDe air-cooled diesel engine from a Type 95 Ha-Go.

A top-down view of the Chi-Ni showing the engine deck.


The Chi-Ni was a 3 man vehicle, compared to the 4 of the Chi-Ha. The commander of the vehicle was positioned in the turret, which was offset to the left of the tank. The turret was so small that he also had to act as loader and gunner to the 57mm gun. Directly below and slightly in front of the commander sat the driver. With no room in the turret for a coaxial machine gun, the third crew member sat on the driver’s right who would operate the ball mounted 7.7 × 5.8mm Arisaka Type 97 machine gun. These two crew members would have been relatively well protected from enemy fire.

This image shows just how off-centre the turret is. Source:

Losing to the Chi-Ha

At the time of its conception, the Chi-Ni was considered the superior tank as it was so much lighter and cheaper to build. However, whilst the Chi-Ni and Chi-Ha trials were in progress, the Marco Polo Bridge Incident occurred on July 7th 1937, marking the start of the Second Sino-Japanese War.

The Chi-Ha undergoing mobility trials. Source: The Koku-Fan, Oct. 1968

Peacetime budgetary limitations evaporated with the outbreak of these hostilities with China. With this, the somewhat more powerful and expensive Type 97 Chi-Ha was accepted for development and service as the Imperial Japanese Army’s new medium tank. It would go on to become one of Japan’s most highly produced tanks.

Only one Chi-Ni prototype was ever built and its fate is unknown. It is likely that it was broken down and recycled with its parts put back into circulation.

Originally Published November 27th 2016

Illustration of the Type 97 Chi-Ni by Andrei ‘Octo10’ Kirushkin, funded by our Patreon Campaign.

Type 97 Chi-Ni

Dimensions 17 ft 3 in x 7 ft 4 in x 7 ft 8 in (5.26 m x 2.33 m x 2.35 m)
Crew 3 (driver, commander, machine-gunner)
Propulsion 135hp Mitsubishi diesel engine
Speed 17 mph (27 km/h)
Armament Type 97 57mm Tank Gun
7.7×58mm Arisaka Type 97 machine gun
Armor 8-25 mm (0.3 – 0.9 in)
Total production 1 Prototype


Chi-Ni on
Japanese Tank Development
AJ Press, Japanese Armor Vol. 2, Andrzej Tomczyk
Osprey Publishing, New Vanguard #137: Japanese Tanks 1939-45.
Profile Publications Ltd. AFV/Weapons #49: Japanese Medium Tanks, Lt.Gen Tomio Hara.
Bunrin-Do Co. Ltd, The Koku-Fan, October 1968

WW2 Japanese Prototypes


Japanese Armoured car Japan (1941-1943)
Super Heavy Tank – 1 built


Hello, dear reader! Due to the constantly changing nature of this subject, this article has gone out of date. New discoveries have changed the story of the O-I significantly. A revised version of this article is in progress that will include translations of the original documents from Japanese into English. This is a very time-consuming process so please bear with us.

The O-I is a very obscure tank, with very little written on it and few original surviving documents. Even fewer documents can be accessed as they are owned by FineMolds, a private company in Japan. The information presented here has been cobbled together using surviving information to give the best possible assessment of the tank. This article does not incorporate the mountains of misinformation that have surfaced in recent years from rekindled interest in these tanks. Information for the developement the O-I leans heavily on Shigeo Otaka, who had first-hand knowledge of its development and has shared his story. However, it must be said that the recollections of an engineer do not implicitly reflect the entire historical truth, and could be distorted by time or other factors.

Go Big or Go Home

After Japan’s defeat at the Battle of Khalkhin Gol, the army realized its current tanks, the Type 97 Chi-Ha and Type 95 Ha-Go, were no longer competitive against the more modern tanks of the Red Army. Hideo Iwakuro, Chief of Army Affairs, instructed Colonel Murata, head of the 4th Technical Research Institute (an organization for tank development in Japan), to construct a super-heavy tank. Hideo Iwakuro’s exact words were “I want a huge tank built which can be used as a mobile pillbox in the wide-open plains of Manchuria; Top Secret…make the dimensions twice that of today’s tanks”. At the time of this request, the biggest tank in Japan was the modest Type 95 Heavy Tank. This leap in size from 26 tons to what would be over 100 tons worried Colonel Murata’s engineers, but each man kept their doubts to themselves.

The Mi-To Super Heavy Tank

Early Mi-To developmental logbook from Mitsubishi
Early Mi-To developmental logbook from Mitsubishi – Source
In March 1941, the initial design work was complete and the tank was ready to be built. The following month, select engineers, including Shigeo Otaka, were taken to the 4th Technical Research Institute’s Headquarters in Tokyo.  The engineers were told not to speak of what they would see and were guided through the dimly-lit barracks into a soundproof room with no windows, where they would later conduct meetings on the tank’s construction. The only entry to the room was a set of double doors (like an airlock), designed to protect the room’s secrecy from observers. Each officer present at the meeting had a separate piece of the design, that once assembled, revealed the whole tank. The tank’s name was Mi-To, for Mitsubishi, the company behind the construction and design, and the city of Tokyo.
Engineer Shigeo Otaka gave the tank’s parameters as 10 meters in length, 4.2 meters in width, and 4 meters in height (or 2.5 meters without the turret). The width of the tracks was 800 mm (although some sources state 900 mm). Propulsion would be provided by two Kawasaki Ha-9 air-cooled gasoline engines, placed parallel lengthwise in the hull, each producing 550 hp for a total of 1,100 hp.  The transmission was a scaled-up version of that used on the Type 97 Chi-Ha. It was mounted in the rear, between and behind the engines with five forward gears plus reverse. The suspension consisted of two coil spring bogies per side, each having two sets of four all-steel road wheels (four on the inside of the track teeth, four on the outside) for a total of eight pairs of road wheels per side.
The tank was armed with a Type 96 15 cm howitzer in the main turret. In front of the main turret were two mini-turrets, each having a 47 mm Type 1 Tank Gun. A fourth turret with dual Type 97 machine guns was placed above the transmission in the rear.  The armor was appropriate for a mobile bunker; 150 mm at the front, made by bolting an additional 75 mm plate to the tank’s 75 mm frontal hull. The side hull armor was only 35 mm thick, with an additional 35 mm side skirt covering the entire side and tracks.  On the inside, there was enough room for a man to stand comfortably. Two 16 mm bulkheads (other sources claim 20 mm) divided the tank into three sections, driver’s compartment, main turret fighting compartment, and engine compartment.


The following dates are not sourced. On April 14th, 1941, construction started on the Mi-To.  Colonel Murata’s plan was for construction to last only 3 months, however problems were found with the tank’s cooling system which delayed construction until January 1942. The hull was completed on January 8, 1942 while Mitsubishi manufactured the turrets. Unforeseen problems again delayed construction, and the tank would not be ready until a year later.
Budget table for improvements that could be made to the dive system. It is easy to tell that the Mi-To project was lacking funds as many of these proposals involve reusing old parts and manufacturing new parts from old materials in order to save money.
Budget table for improvements to the dive system. It is easy to tell that the Mi-To project was lacking funds as many of these proposals involve reusing old parts and manufacturing new parts from old materials to save money. – Source
For testing, the Mi-To was shipped to Sagami Armory (modern day Sagami General Depot) in Sagamihara, 51 km (31.7 miles) south of Tokyo. Only the people involved in the development of the tank participated in the transport, making it very difficult. In June 1943, the tank was disassembled for transport and covered with an awning to keep it hidden. Work on moving the tank started in at 2:00 am every day and lasted until dawn.  Transport took 10 days and it arrived at Sagami Armory at the end of June with tests scheduled for August 1, 1943.


About the time the Mi-To was completed and trials were scheduled, the Army assigned it the name O-I. Following Japanese tank nomenclature, I stands for “first”, and O for “Ooki-I-gou”, Japanese for “big”. This was the only time “O” was used as a tank type. While the Army’s designation was O-I, Mitsubishi’s internal designation continued to be Mi-To.
While it is not specifically recorded that tests were conducted on August 1st, this can be inferred from a fragmentary piece of evidence which states that the testing team ate lunch at 2:30 pm on August 1st. The O-I’s trials took place without the additional 75 mm bolt-on frontal armor and without the main turret, as the 35 mm roof plate was not ready. These exclusions meant the tank weighed only 96 tons. On the day of testing Colonel Murata was deployed at the front, so in his place for observation was Lieutenant Colonel Hidemitsu Nakano. Also present was the chief of Sagami Armory, Tomio Hara.
The testing grounds were the road and field north of the 4th Technical Research Institute’s building. The ground was soft during off-road portions of the tests and the O-I’s tracks sunk into the ground up to a meter. The tank tried to free itself, causing it to sink further and damage the suspension. Following the test, a full bow with both hands to the ground was made to the repair department chief.
O-I test driving schedule, August 1943
O-I test driving schedule, August 1943 – Source
After the tank was pulled out, tests continued on a concrete road, but because of the damage to the suspension the tank tore up the road and damaged its suspension further. The tests were abandoned and the tank was left and covered with a tarpaulin. The O-I was disassembled for scrap between August 3-8 of 1943, or more likely, in 1944. All that remains of the O-I is a single track link, measuring about 800 mm in width, and 300 mm in pitch. It was previously at Wakajishi Shrine but has since been moved to JGSDF Camp Takigahara.


There was a post-war questioning with four Mitsubishi engineers who worked on the Mi-To, but the only one identified so far is Shinjo Masahisa. Unfortunately, these men did not have much to say about the O-I, and what they did say conflicts with proper sources. The only information they could provide was that the Mi-To had 100 mm of frontal armor, and could reach 40 km/h on roads. Both of these numbers seem incorrect as all other sources state the tank’s armor was 75+75mm and it had a top speed of 30 km/h and their higher claimed speed seems very optimistic for such a heavy tank.
Sagami Armory Chief, Tomio Hara reports the Mi-To as having a 10 cm (10 cm often refers to 105 mm in Japanese gun terminology) main gun, but blueprints show a short 150 mm howitzer. There is also an unverified claim of the tank’s size with a length of 10.1 meters, width of 4.8 meters, and height of 3.6 meters.
The dimensions of the track links are very unclear. One source states the tracks were 900 mm wide, another states 800 mm. Assuming the tank is 4.2 meters wide, then by comparing the hull to the tracks on blueprints, the tracks work out to 660 mm,  however this is too small for such a heavy tank. It is likely that the blueprints only show the run of the tracks, and not the complete width of the links themselves. The single surviving track link measures 800 mm wide, this would seem to be the correct number.
The blueprint’s cutaway side view of the frontal armor is clearly not 75 mm thick which has caused deliberation regarding if the armor on the blueprint is correct among the TankEncyclopedia team. It is likely that the blueprint only shows structural steel, as the Japanese often built tanks by constructing a 35 mm skeleton before welding on armor. However, the frontal towing hooks can be seen attached to this 35 mm plate on the blueprint and tow hooks are normally attached to the armor, not the structural steel. It is possible this was a mistake in the blueprints.

Surviving O-I blueprint
Surviving O-I blueprint – Source

Surviving O-I blueprint
Surviving O-I blueprint – Source

Surviving O-I blueprint
Surviving O-I blueprint – Source

Surviving O-I cutaway blueprint
Surviving O-I cutaway blueprint – Source

Surviving O-I cutaway blueprint
Surviving O-I cutaway blueprint – Source

Detailed view of the O-I's suspension
Detailed view of the O-I’s suspension – Source

O-I driver's periscope
O-I driver’s periscope – Source

Tow bar specifically made for the O-I
Tow bar specifically made for the O-I – Source

Surviving O-I track link
Surviving Mi-To track – Source

O-I specifications

Dimensions (L x W x H) 10 x 4.2 x 4 m (32.8 x 13.8 x 13.1 ft)
Total weight, battle ready 120+ tons
Crew 11 (driver, co-driver, commander, main turret gunner, 2x main turret loaders,
2x 47 mm turret operators, machine gun turret operator, radioman, engineer)
Propulsion 2x 550 hp Kawasaki Ha-9 air-cooled gasoline engines
Suspension Coil springs
Speed (road) 30 km/h (18.6 mph) (Probably an optimistic number)
Armament 150 mm (5.9 in) Type 96 howitzer
2x 47 mm (1.85 in) Type 1 tank guns
2x 7.7 mm (0.3 in) Type 97 heavy tank machine guns
Armor 75+75 mm (2.95 + 2.95 in) frontal armor
35+35 mm (1.38 + 1.38 in) side armor
Total production 1 incomplete prototype
For information about abbreviations check the Lexical Index

About the article

The Tanks Encyclopedia team has spent many hours debating internally about the O-I. Many different opinions were fielded and in the end we agreed to put it aside until more information was discovered. Recently, new information has come to light; which has led to a restructuring and improvement of the article.
Most older sources and representations of the O-I are now completely out of date. Both the 100 ton tank (sometimes called O-Ni even though this designation was never used), and the 140-150 ton O-I (sometimes called O-Ho) are known to be incorrect representations of the O-I. In recent years it was discovered that original documents of the O-I’s development survived the War. These documents were purchased by the model kit company FineMolds. FineMolds allowed people to see them, but only at FineMolds’ headquarters in Japan and to pay a considerable sum of money to access the documents. This led to many new claims regarding the O-I, but by those who would often refuse to reveal their sources, since they had spent money to acquire them. In late 2016 however, a Chinese author, Tang Qian, brought forward some of FineMolds’ documents in his own article and while it is not a complete set of documents, it does give us some proof and history of the O-I superheavy tank.


Tank and Tank Battles – Shigeo Otaka
Pacific War Secrets: All Japanese Secret Weapons, 2008
Imperial Japanese Army Land Weapon Guide, 1997
Japanese Tanks – Tomio Hara, 1978
Japanese Ground Cannons: Heavy Field Cannons – Sayama Jiro, 2012
The Japanese Superheavy Tanks on For the Record
The O-I on the Warthunder Forums
Finemolds Documents Brought to Light by Tang Qian

Tanks Encylopedia’s own illustration of the O-I

WW2 Japanese Prototypes

Type 91 & Type 95 Heavy

Japan (1935)
Prototype Heavy Tanks – 4 built

During 1930s, fears were strong among the most powerful military nations that a coming war would develop along the same lines as WWI. No one wanted another war rife with stalemates, no one moving for months on end due to swamp like terrain, and constant machine gun bombardment. As such, tank designs of the period were heavily set on infantry support, being large, slow moving and bristling with anti-personal weaponry. The era became awash with the fad of multi-turret tank designs, with all of the most powerful countries adopting them in one form or the other.

The A1E1 Independent for the British Empire, the Großtraktor or Neubaufahrzeug for Nazi Germany, and the T-35 of the Soviet Union are prime examples of this design fashion. One might even consider the mobile machine-gun nest that was the United States’ M2 Medium to be part of the group.
Imperial Japan was no exception to the rule, coming up with their own design in 1934. This was the Type 95 Heavy Tank (タイプ95重タンク, Taipu 95-jū tanku).

The Experimental Tank No. 1, Type 87 Chi-I.
The roots of the Type 95 Heavy begin with the first tank the Japanese Military produced independently, the Experimental Tank No.1 (実験タンク番号壱, Jikken tanku bangō wən), also known as the Type 87 Chi-I. This ancestor to all Japanese tanks was built in 1927, and was classed by the Military as a Medium Tank. It didn’t progress further than the prototype phase, however.

The Type 91

The first prototype of this heavy tank was built in 1931 and was designated the Type 91. This was an 18-ton vehicle, powered by a 6-cylinder BMW IV inline engine that ran on gasoline. The engine was likely purchased from Germany. The tank had 3 turrets, a main one in the center armed with a 57 mm (2.24 in) cannon, and 2 secondary forward and rear turrets armed with 6.5 mm (0.26 in) machine guns. It also had an armor 8 – 17 mm thick.
The Prototype vehicle Type 91, undergoing crossing trials
The Prototype vehicle Type 91, undergoing crossing trials. The complicated suspension can be seen here.
A feature carried over from the Type 87 Chi-I was the rather complicated parallelogram suspension system with two pairs of road wheels per leaf-sprung bogie. There were 17 road wheels per side, giving it a total of 34 road wheels. The parallelogram type of suspension is more commonly known as Swing arm suspension, which is mostly used on motorcycles.
The Type 91 proved to be an unsuccessful endeavor, and the project was soon canceled. The lessons learned were passed on to the Type 95.

Type 95 Heavy, Design and Development

Imperial Japan felt that the increasingly powerful Soviet Union could be a potential future enemy. As such, work once more resumed on a heavy tank for the Imperial Japanese Army (IJA) to match the Red Army’s T-35 heavy tank.
The development of the Type 95 Heavy began in 1932, with a prototype not being complete until 1934. The overall structure of the chassis and module layout was much the same as the previous Type 91 prototype. However, it was given significantly thicker armor, thicker than all of Japan’s other tanks of the era. The turret face was 30 mm, with 25 mm on the sides and the rear. The upper plate bore the thickest armor at 35 mm. The sides weren’t lacking either as they were 30mm thick with a further 25mm on the rear of the vehicle.
This amount of armor increased the weight of the vehicle to 26 tons, the heaviest tank Japan had yet built.
The suspension was also altered, with a much simpler form of leaf-spring suspension. The amount of road wheels was drastically reduced, down to 9 a side, giving it a total of 18. This was found to give the same performance, while being much less complicated.

The Type 95 during trials, showing how the suspension operates.

A 3D model of the Type 91 Heavy by Giganaut

Tanks Encyclopedia’s rendition of the Type 91 Heavy by David Bocquelet.
Tanks Encyclopedia’s rendition of the Type 95 Heavy by Jarosław Janas.


Like the legendary samurai of ancient Japan, the Type 95 Heavy would carry 3 weapons into battle. For a Katana, its main weapon mounted in the primary turret, a unique Type 94 7cm tank gun. It’s Wakizashi, a secondary weapon, a Type 94 37mm (3.7cm) cannon mounted in the forward turret. And finally, its Tantō, the third weapon, a 6.5mm machine gun mounted in the rear turret.

The 7cm gun was a short-barreled type, able to fire both Type 92 HE (High-Explosive) shells and Type 95 AP (Armor-Piercing) shells. Further ballistic data is unknown. The Type 94 37mm cannon is the same as equipped on the Type 95 Ha-Go light tank, with average armor penetration 36 mm (1.4 in) at a distance of 275 m.


The vehicle did go through trials in 1935, and performed well. Production was limited to only 4 vehicles, however, due to logistical and practical reasons. High-speed lighter tanks, more suited to Japanese tank doctrine were starting to come along, such as the Type 95 Ha-Go.
With only 4 Type 95 heavies built by 1934, the project was canceled. It was considered too slow and much too big. Also, it was soon apparent that a multi-turret tank design was a less than practical concept. It is rumored that at least one of the vehicles took part in a parade in Tokyo in 1935. This was part of the Yasukuni Military Expo during which Japan showed many of their newest armored vehicles.

A disarmed Type 95 at the Yasukuni Shrine.
This wouldn’t be the end of the Japanese work on heavy tanks, however. The next generation of such vehicles in Japan would be “Super Heavies”. This would include vehicles such as the O-I Super Heavy Tank.
None of the Type 95s survive today, though one was kept at the Chiba as a training vehicle up to 1945.


As limited as the production of this vehicle was, Self-Propelled Gun (SPG) variants were conceptualized, with 2 chassis handed over to Mitsubishi Heavy Industries for testing.

These chassis became the bases of the Ji-Ro/Ji-Ro Sha (Left) and the Hi-Ro-Sha (Right). These Tank Destroyer variants were mounted the powerful Type 14 105mm Gun, also known as the “10-cm cannon”. The Hi-Ro Sha was an open top vehicle, with the 105mm gun munted at the front behind a small gun shield. The Ji-Ro/Ji-Ro Sha was a bit more of an extensive modification. A large case-mate was placed on the rear of the tank, with the 105mm mounted inside. While the Hi-Ro did reach the Prototype phase, it is unclear wether the Ji-Ro did as well. No photos of it are known.

The Prototype Hi-Ro/Hi-Ro Sha. While there are a few photos of this vehicle, none seem to remain of the Ji-Ro. Photo: –

An article by Mark Nash

Type 95 Heavy Specifications

Dimensions (L-W-H) 6.47m x 2.7m x 2.9m (21ft 2in x 8ft 8in x 9ft 5in).
Total weight, battle ready 26 tons
Crew 5 (commander, gunner, loader, driver, forward gunner, rear gunner)
Propulsion BMW IV water-cooled inline six-cylinder gasoline engine
Speed 22 km/h (14 mph)
Armor 12 – 35 mm (0.47 – 1.37 in)
Armament Type 94 7cm Tank Gun, Type 94 37mm Tank gun, x2 6mm machine guns. (1 on the rear of the primary turret, 1 in the rear turret)
Total production 4

Links & Resources

Type 91 & 95 Heavy on IKAZUCHI
The Type 95 Heavy on the Japanese Wikipedia
Osprey Publishing, New Vanguard #137: Japanese Tanks 1939-1945
Delta Publishing, Ground Power #41, Japanese military vehicles of the Second World War

WW2 Japanese Prototypes

Type 5 Ke-Ho

Japan (1944-45)
Light tank – 1 Built

Although it had performed well before the outbreak of the Second World War, and during it’s early stages, the Type 95 Ha-Go was showing it’s age by 1942. It simply didn’t stand a chance against the increasingly powerful tanks being fielded by the Americans in the Pacific, and later, the Soviets in Northern Manchuria.

Between 1942 and 1943, attempts had been made to replace it with a new light tank. This resulted in the Type 98 Ke-Ni and Type 2 Ke-To, respectively. However, these projects failed to fully materialize with only 104 Ke-Ni and 34 Ke-Tos built by the end of the war.

Following this, the IJA decided to try again and work started on the Type 5 Ke-Ho (五式軽戦車 ケホ Go-Shiki Keisensha Keho). It was the last light tank designed by the Imperial Japanese Army (IJA).

A scale drawing of the Ke-Ho. Source:


The Ke-To experimented with a slightly better main armament in the form of Type 1 37 mm (1.46 in) gun. This offered a much-needed improvement over the Type 94 37 mm (1.46 in) used on the Ha-Go. Though a step in the right direction, this weapon still was not enough to combat the M4 at any angle. The quest to mount the new Type 1 47mm tank gun on a fast, mobile chassis began in 1942. Up till then, the Ha-Go had performed well against American M3 Light tanks, but began to suffer as more heavily armored tanks began to appear such as the M5 Stuart and the larger M4 medium tank. The Ha-Go’s last successful engagement was against Ameican forces on the Bataan Peninsula in December 1941. A force equipped with M3 Stuart Light tanks.

It was projected that this new light tank would have a 4-man crew. This consisted of the Driver (front right hull), bow gunner (front left hull), the Commander who also acted as loader (right turret) and the gunner (left turret).



The Hull of the Ke-Ho was based on an enlarged Ke-Ni/Ke-To chassis. It utilized a miniaturized bell-crank suspension, based on that of the Chi-Ha/Chi-He with 6 road-wheels per-side, 3 return rollers and a rear mounted idler wheel. The bell-crank suspension consists of bogies mounted on arms, which in turn are connected to a long spring on the side of the hull. The bogies push against each other when passing over terrain, allowing the bogies to actuate. The Ke-Ho was powered by a 150hp Type 100 air-cooled diesel engine. Despite its heavier weight, the Ke-Ho would still be able to travel at a top speed of 50-55 km/h (31 – 34 mph). Like the majority of Second World War Japanese armor, the engine was placed in the rear with the transmission and drive sprockets at the front.


The turret planned for use on the Ke-Ho was based on the original Chi-He design, which in turn was based on the Chi-Ha Shinhoto’s. It had a long, square rear with a rounded turret face. There was a cupola on the right side of the roof with a two-part hatch and vision periscopes for the commander. The tank would be armed with the Type 1 47mm tank gun, as used on the Chi-Ha Shinhoto and initial models of the Chi-He. This gun had a muzzle velocity of 840 m/s (2,723 ft/s) and could penetrate a maximum of 55 mm (2.2 in) at 100 meters (328 feet). It was equipped with both Armor-Piercing High-Explosive (APHE) rounds and High-Explosive (HE) rounds. Although this gun was a huge improvement over the 37mm of the Ha-Go, it was still not enough to combat the front of an M4. It is likely that if the Ke-Ho made it to combat, it would have to exploit the same flanking, close quarters ambushes utilized by Shinhoto Chi-Has. Although the maneuverabiity of the Ke-Ho would of made that task much easier.

The Type 1 47mm Tank Gun. Photo: The Koku-Fan, Oct. ’68

Secondary armament consisted of two Type 97 7.7mm machine guns. One of these was located in a ball mount on the front left of the hull, operated by the bow-gunner. The other was located in the right-rear corner of the turret bustle, operated by the loader. Either of these guns could be dismounted and placed atop a mount next to the commander’s cupola.


One of the major shortcomings of the Ha-Go which designers sought to address was the fact that with a maximum of just 12mm (.47 in) thick armor, a .50 cal (12.7 mm) machine gun could effectively knock one out. The Type 98 Ke-Ni and Type 2 Ke-To had somewhat of an armor upgrade, with a maximum of 16mm (.62 in). However, this was still not enough to reliably counter .50 cal rounds. As such the, Ke-Ho would have an even greater increase to armor thickness, being at least 20 to 50 mm (.78 in – 1.9 in) thick, more than enough to stop a .50 caliber round.



A planned variant of the Ke-Ho was the Ku-Se (自走砲 Jisōhō クーセ) self-propelled gun/tank destroyer. It was to be armed with a Short Type 99 75 mm mountain gun, in a similar open case mate to the planned Ho-Ni and Ho-Ro SPGs.

Drawing of the Ku-Se variant. Source:


In 1942, a prototype vehicle was built, and the project was canceled soon after. As with most new tank designs the Japanese came up with, it was low on the list of importance. Resources and construction efforts were instead being focused on warships and warplanes. Mass production was approved in 1945 however, but this was of course too late and the one prototype remained the only one built. This also meant that the Ku-Se variant never left the drawing board.

A post-war drawing of the Ke-Ho. Source: – N/A

What happened to the prototype is unknown. It was likely taken back to the USA for analysis and later broken down.

Illustration of the Type 5 Ke-Ho based on available drawings. Note the miniature bell-crank suspension and the early Chi-He turret armed with the Type 1 47mm gun. The placement of a jack and pioneer tools on the left rear fender is speculative. However, it is also based on the known placement of such items on other Japanese tanks of the era. This Illustration was produced by Brian Gaydos, funded by our Patreon Campaign.

Known Specifications

Dimensions 4.38 meters long
Weight 9 tonnes
Crew 4 (driver, gunner, commander, bow gunner)
Propulsion 150hp Type 100 Air-Cooled Diesel
Speed (road) 50 km/h (31 mph)
Armament Type 1 47mm Tank Gun
2x Type 97 7.7 mm machine guns
Armor 20 mm – 50 mm (0.78 – 1.9 in)
Total production 1 Prototype


Osprey Publishing, New Vanguard #137: Japanese Tanks 1939-1945
Profile Publications Ltd. AFV/Weapons #49: Japanese Medium Tanks, Lt.Gen Tomio Hara.
Profile Publications Ltd. AFV/Weapons #54: Japanese Combat Cars, Light Tanks and Tankettes, Lt.Gen Tomio Hara
Bunrin-Do Co. Ltd, The Koku-Fan, October 1968