Hello everyone. The last time I posted a write on the Ho-Ri tank was on November 14th, of 2016. Since then my studies on the project have been underway for quite some time. Earlier this year, I obtained documentation files on the tank project from a private collection. In my findings were official schematics and outline drawings of the Ho-Ri tank destroyer, alongside two photographs of the vehicles construction. However I was not given the permission needed to obtain rights to these photographs, I was able to secure property rights to its drawings. Which unfortunately, I do not plan to release publicly for the time being.
This article will be a brief historical background on the Ho-Ri as of what I have learned since last year. The previous article, no longer being completely up-to-date, will be edited as such and forwarded to this new post - as to clear future confusion. I hope you all enjoy!
- Information on vehicle accurate as of [9/3/2017] -
As the war progressed in the Far East, it became increasingly evident that Japan’s armored warfare doctrine would not suffice against the growing threat from the United States. Prior to America’s declaration of war on Japan, tank doctrine focused solely on the infantry support role during an offensive. Much of the Japanese armor inventory in 1941 was already a decade old. Poorly armed and armored, these Japanese infantry tanks could not counter the M4 Sherman. To remedy this, Japan quickly introduced the Chi-Ha Kai with a 4.7cm anti-tank gun, but it was only a temporary solution.
|Japanese crew manual on the M6 Heavy Tank.|
This new policy focused on the development and deployment of a common medium tank with stronger armament, which would in turn be supported by tank-destroyers with high-caliber weaponry. In furtherance of this policy, both medium and large caliber anti-tank guns were developed for use in new medium tank designs in 1943. Two medium tank designs were selected, the Chi-To and Chi-Ri tanks both adopted their versions of the Type 5 75mm guns.
Development of the Ho-Ri began in late 1943, using the chassis of the Chi-Ri as the base for development. Japan’s 4th Technical Institute of Research understood that the Chi-Ri’s relatively flat front hull plates offered little protection against enemy anti-tank fire. Initial tank designs kept an unchanged hull design, and replacing the turret with a welded casemate. A key focal point in the design of the Ho-Ri was the decision to angle the front armor plate to 70 degrees, drastically increasing the effective armor protection and enabling the vehicle to withstand American 76mm guns.
The concept was presented to the Ministry of War in early 1944 in the form of a wooden mockup. The staff had expressed positive opinions on the vehicle design. Following the presentation, the order to construct a prototype of the Ho-Ri was approved. It took until July for the chassis to be completed. In August, the Ho-Ri prototype had been assembled and put through trials.
|National Archive File Ref. C14011075200|
The National Institute for Defense Studies
Ministry of Defense, Military Administration
of Ordnance, 4th Technical Research Institute
Report Ho-Ri Prototype.
The Ho-Ri prototype mounted an Experimental High Velocity 10.5cm anti-tank gun, which featured a semi-autoloader mechanism to reduce the strain of loading the heavy shells. The gun was designed to counter all fielded armored vehicles the Unites States had in its possession. Japanese Intelligence had been aware of the possible deployment of the M26 Pershing and the M6 Heavy tank in the pacific for the invasion of the mainland. Due to the size of the 10.5cm cannon, natural depression was limited to only a couple degrees. To counter this, there was a top roof hatch that opened by pin to allow full depression of the gun.
The gun was required to effectively penetrate and destroy these tanks at all reasonable combat ranges at most angles. Development of this Experimental 10.5cm anti tank gun was initiated on July 30th, 1943. One member of the development team was a Major of the Army Weapons Administrative Division, and had stated in his records the gun had to achieve a performance figure of 200 millimeters of penetration against RHA at a range of 1,000 meters. With this demand being kept in mind, the first prototype cannon was completed and tested in February of 1944. It lacked sufficient performance, only being able to fire at a muzzle velocity of 916 m/s. It was only capable of penetrating 150 millimeters of armor at the trial range of 1,000 meters. Without a ballistic cap, the performance of its APHE shell at certain angles was drastically poor. The Munitions Council had to alter the design of the experimental gun and work on producing a new one for the Ho-Ri project.
|The Ho-Ri tank as drawn by Tomio Hara.|
After trials were conducted with the constructed prototype, the Ho-Ri was approved for planned production, and was to be officially adopted into service under the designation Type 5. The Army Weapons Administrative Division listed concerns they had in mind with the prototype to be adjusted with the production of the main series of tank destroyers. Due to rapid development of American anti-tank weaponry, it was ordered to increase the thickness of the Ho-Ri’s armor. However due to the war's end drawing near for Japan, the lack of materials presented an issue for a quantitative supply of Ho-Ri units to be supplied to tank regiments. The choice was then made to limit the number of production models and for them to be kept reserved in vital focal areas of the Japanese mainland. This order was in line with the limited production run of the Chi-To and Chi-Ri tanks.
|National Archive File Ref.C13120839500, The National Institute for Defense Studies, Ministry of Defense,|
Military Administration of Munitions Mobilization, Production Chart of January to April of 1945.
The thickness of the front hull plate was increased to 120 millimeters for the production model. The sides and angled plating around the vehicle were thickened to a considerable degree as well. This caused the vehicle to have a drastic increase in weight and it would have been underpowered with the old engine. To compensate for the added weight, an Experimental Kawasaki V12 engine with an output of 1,100 horsepower was added. This kept the mobility of the production model Ho-Ri on par with that of the original prototype.
The Experimental 10.5cm anti-tank cannon continued to be developed by the Munitions Council throughout 1944. In December of the same year, the project was once again at a testing phase with a new prototype gun. Performance of this gun reached the required standards - 200 millimeters of penetration at 1,000 meters with a muzzle velocity of 1,005 m/s. The gun was supplied with the Type 2 APHE shell with a ballistic cap to support the trajectory of the shot. It was accepted into service as the Type 5 10.5cm Tank Gun. By the wars end, only a few models of the gun were produced. And a limited supply of tank rounds.
Production of the Type 5 Ho-Ri began in January of 1945. By March, a total of 5 Ho-Ri tanks had been completed; further production of the vehicle was halted by American bombing raids. Japan would not be able to continue production of the vehicles as the Japanese war effort was almost bled dry by this point. The 5 completed Ho-Ri’s were kept with the Chi-Ri and Chi-To tanks at local armories. None of the vehicles were given to standard tank groups. Instead they remained as property under the Munitions Council and supervised by officers of the local battalions.
|Lake Hamana in Shizuoka Prefecture. The town has a|
reputation for its mysterious sunken tanks deep
in the lakebed.
By the end of the war almost all Ho-Ri’s and other end war vehicles were either scrapped, destroyed, or sunk. Leftover prototype and testbed vehicles were captured and brought back to the United States where after being evaluated, quickly scrapped for parts in the years following. As of September 3rd, 2017, there are currently only 2 photographs of the Ho-Ri’s in possession of private collections. Public access to these photographs and other documentation (such as the blueprints and data sheets) are now under review.
- Information on vehicle accurate as of [9/3/2017] -