[WT] Type3 Ho-Ni III

To the unexpected majority of players, Gaijin released the first Japanese tank destroyer devblog today. Many expected Japan to not have a tank destroyer branch with the initial release of the ground forces, as was done with Britain and the United States. Japan focused heavily on anti tank vehicles throughout the war, and today we get to look at one of the most known, the Ho-Ni III. 

This is the first time Gaijin showns Japan's late war base paint, Olive. 

In 1939, Japan had grown to understand the need for an anti tank vehicle in the field. The Type97 Chi-Ha with its 57mm cannon was not sufficient in providing support to the infantry against armoured adversaries. Unlike the Battle of Nanchang, where the Japanese tanks were first used successfully as infantry support against the Nationalist Chinese, the Nomonhan Incident against the Soviets had illustrated the need for an anti tank role'd vehicle. After the Japanese defeat at Nomonhan, the Imperial Japanese military initiated a project to design two types of tanks, an anti tank replacement of the Chi-Ha and a self propelled gun chassis with heavy firepower against armour at range. In December of 39, the two projects were called Ho-I and Ho-Ni.

Ho-Ni I prototype during trials. 

The Ho-Ni was designed to be a self propelled gun mounting the Type90 75mm field gun. The development of the Ho-Ni was given to the 1st Army Research Institute, which was the go-to research group involving SPG designing. The Type97 Chi-Ha chassis was selected to be used to produce this tank. However due to resource shortages and the introduction of the Chi-Ha Kai and its anti tank 47mm, the Ho-Ni project was halted for a year. It took until 1941 for the prototype to finish. The prototype used an open thin shielding to replace the turret and was kept practically identical to the original chassis. The prototype finished testing in
 October and was labeled Ho-Ni I.

During the prototype trial tests of the Ho-Ni I, the crew compartment openness and the lack of direct fire scope proved to be an issue to the Army. However due to the need of a tank destroyer, the tank entered production and would not have these problems dealt with until mid 1943. It was only then the Imperial Japanese Army had no choice but to upgrade their tank, as it proved too difficult to target tanks at range. In 1944, a prototype was completed and was approved for service. This tank was named Ho-Ni III (II was a variant of the I adding a new cannon, III was a separate tank).

Rear of the Ho-Ni III.

The gun shields on the original Ho-Ni models were replaced by a single heptagonal superstructure consisting of a thickened frontal plate accompanied by two plate cheeks. Two sides plates, and two rear plates constituted at an angle. The thickness of the new superstructure was limited to only 25mm. This wasn't made to withstand tank shells, but rather simply protection against machine guns and other light anti tank weapons. Because the width of the turret is wider than the upper part of the car body, the left and right sides of the turret were overhanging from the car body. At first glance the superstructure appears to be able to turn around the whole circumference as if it was a turret, but in fact it only had a limited swivel for the main cannon.

Pistol and view ports were placed around the superstructural plating. A hatch with a rectangular and a crab shear type door above the gunner´s position allowed using an indirect fire sight. Unlike the original models, the Ho-Ni III added finally the gun sight into the mount as to provide accurate fire. The gun of the tank was a revamped Type90, the Type3 75mm anti tank gun. It is most commonly known for its use with the Chi-Nu medium tank. However, the gun had a weight of 1,000kg with a 75 x 424R shell cartridge. The standard armor piercing projectile was an APHE shell (Type1 APHE) found with many Japanese tanks throughout the war. It had a shell weight of 6,600 grams and was capable of penetrating 84mm of RHA at a distance of 500 yards. According to the U.S Military in August 1945, the armor piercing capability of the Type90 anti-tank artillery cannon (again, identical to the Model I and II of the Type3 75mm) is provided through a set of APHE shells, which can penetrate:

Ho-Ni III outline. The tank had -15 gun depression.

(at a 90 degree angle of impact)
2.4 inches (61 mm) at 1,400 yards(about 1371.6 m)
2.8 inches (71 mm) at 1,000 yards (about 914.4 m)
3.0 inches (76mm) at 750 yards (about 685.8m)
3.3 inches (83 mm) at 500 yards (about 457.2 m)
3.5 inches (89 mm) at 250 yards (about 228.6 m)


The muzzle velocity was 668 meters per second.   The testing results of the Type1 APHE shell were mediocre and did not meet the requirements of the cannon. To improve on this, the Army developed a Tungsten-Chromium steel anti-tank shell known as the Type1 AP Tokko Ko. This shell had an improved muzzle velocity of 683 m/s and was capable of penetrating 100mm of RHA at 500 yards, and 85mm at 1000 yards.  The Kou was made of nickel chrome molybdenum steel mixed with molybdenum for nickel resource conservation due to Japan's lack of available resources at the time.


The Ho-Ni III, by the time it entered production in 44, was restricted to use only in the Japanese home island. Total number of Ho-Ni III's was numbered to 41, and they were issued to the 4th Tank Division during the homeland defense program. All were destroyed and scrapped after Japan's surrender in 1945.

Weight: 17t
Crew: 5 men
Length 5.52  m
Height: 2.37  m
Width: 2.33 m
Engine: Mitsubishi SA 12.2 0 VD
Cylinders: V12 Air cooled Diesel
Power Output: 150 hp/1,500 rpm
Max Speed: 40kmh
Armament: x1 Type3 75mm Model II

Gun Shield Armour:
Mantlet: 60mm
Front - 25mm @ 78°
Cheeks: 25mm @ 78°
Side - 25mm @ 75°
Roof - 10mm @ 10°
Rear - 20mm @ 25°

Hull Armour:
Front - 25mm @ 82°
Side - 12mm @ 75°
Roof - 16mm
Rear - 25mm @ 90°

Suspension:
Front - 25mm
Side - 25mm
Rear - 20mm

[WT] Type2 Ho-I

   Today Gaijin released their first devblog of the week. Although we did see this coming with the accidental preview with the Chi-He developer diary last week. Probably would have had this out hours ago but I had writer's block yesterday, so never got to post anything this past week. Although this week I have a feeling I'll be posting plenty to make it up to you all. But without further ado, today Gaijin shows you the first assault tank of Japan's tech tree, the Type2 Ho-I.

As Japanese tank development expanded over the course of the 30's, the Imperial Japanese Army toyed around with the idea of a tank with the sole purpose of providing artillery support from a self propelled vehicle. As the Second Sino-Japanese war developed, Japan knew they needed a vehicle to rely on for mobile fire support. The concept of a field gun mounted on a tank chassis to breach hostile fortifications with the use of high explosive shells had become popular around this time. Germany would later produce their own tanks of the class such as the early Panzer IV units with their short, low velocity guns.

Type41 Rentai Ho.

Japan had started out well in the conflict with the Nationalist Chinese. Eventually, however, the Japanese began suffering heavy casualties street fighting in major cities such as Shanghai. The battle proven Type89 medium tanks were the standard infantry support at the time, but were crippled by their lack of power with the Type90 57mm tank cannon. Chinese fort towers and pillboxes proved too much for the gun's capabilities.  To combat these targets, the Japanese troops relied on towed mountain guns. However, with mobility now becoming a necessity, Japan decided to develop a new gun to fit on a tank chassis. In 1937, Japan’s4th Technical Research group decided to work on the self propelled gun concept into a gun tank, dubbed Hosensha ("Gun Tank"), or Ho-I.  The Type41 "Rentai Ho" Mountain Gun was chosen by the research group to be modified and extended for use in the tank project. This cannon was a licensed version of the German Krupp M.08.

Type99 75mm Tank Gun Model I.

 By December of 1940, the Type41 Rentai Ho had been redesigned as the Type99 Tank Gun Model I. Keeping the same 75mm caliber, the first model of the gun had a weight of 543kg, loading a 75 x 185R cartridge.  This is the same as the Type41's design, but it was a completely redeveloped artillery cannon which adopted the same horizontal plug as used on the Type94 mountain gun. Therefore, ammunition for Type41 was also accessible to the Type99. However, because of the low muzzle velocity of the Type41, a new standard ammunition tube was developed, which increased the velocity by altering the charge while using the same cartridge as the Type41. As a result, the initial speed increased from 360 m/s to 445 m/s. However, due to resource shortages the Type41's munitions ceased production, hence only the 3 shells developed for the Type99 were issued. These included the Type94 HE and Type 1 APHE.

During the spring of 1941, Hitachi Ltd constructed a prototype of the Ho-I using the Chi-Ha chassis as the basis of the tank. The prototype participated in a series of tests in September, however the Army deemed the tank insufficient as the gun handling was poor against a moving target and the low penetration capabilities were noted as too poor to rely on. The project took a delay as the Type99 tank cannon had to be redeveloped to fit the Army's standards.

Ho-I Prototype during combat trials at the tank school. 

The Ho-I's turret design was based of the Chi-Ha Kai turret, but used a welded construction which was rare among Japanese tank designs at the time. The result was a large box like structure that gave considerable room. As Japanese tank development continued, however, the Chi-Ha chassis slowly became more obsolete as a battle tank. To replace the tank, the Japanese designed the Chi-He medium tank as the new standard for the Army. The Ho-I was decided to instead rely on the Chi-He tank's hull to improve armour conditions.

Type2 Ho-I

The second Ho-I prototype had been completed in December of 1942. The turret was redesigned by Hitachi, Ltd, The upper slope of the turret was removed and the sides had instead been heightened. The side armor plate were now strengthened by supporting rivets. The frontal armour thickness of the turret was increased from 25mm to 50 mm. The front mantlet had also been changed, this time having better angles to deflect enemy projectiles. This time the tank chassis was manufactured by Mitsubishi Heavy Industries, and the gun was modified to be closer to the Army's standards.

The velocity of the Model II gun was increased to 443m/s for the APHE shell, achieving a general number around 70mm of penetration at 100 meters, and kept the Type94 HE shell from the initial tank gun. With the Model II, a HEAT shell was developed for the tank, labeled Type2. The shell was a molded explosive charge that had the capability of 100mm of penetration at all ranges. The Ho-I by 1942 has changed its initial doctrine from infantry fire support and was, rather, a reliable method of engaging the American M4 Sherman with high firepower. In 1943, multiple tests were conducted against a captured M4 tank, and had achieved successful penetration of the tank's front from 800 meters with its HEAT round.

Ho-I with 57mm.
Both 75 and 57 models had -15 degrees.

Despite the success of the cannon, the Army had already began development of an experimental high velocity 57mm anti tank gun Kou for universal use. The Ho-I with the 57mm would later become the first prototype leading to the design of the Type4 Chi-To. However, by the time the Ho-I had entered service in 1943 as the Type2 Ho-I, the tank was kept in reserve with the 4th Tank Division due to the suspected invasion by the Americans. By the war's end in 1945, only 30 units were manufactured, none saw combat, and all were destroyed after.

Weight: 16.7t
Crew: 5 men
Length 5.73 m
Height: 2.58 m
Width: 2.33 m
Engine: Mitsubishi Type100
Cylinders: V12 Air cooled Diesel
Power Output: 240 hp/2,000 rpm
Max Speed: 44kmh
Armament: x1 Type99 57mm , x1 Type97 7.7mm MGs

Turret Armour:
Mantlet: 60mm
Front - 50mm @ 80°
Side - 35mm @ 75°
Roof - 16mm
Rear - 20mm @ 78°

Hull Armour:
Front - 50mm @ 72°
Side - 25mm @ 75°
Roof - 10mm
Rear - 20mm @ 90°

Suspension:
Front - 50mm @ -42°
Side - 25mm @ 90°
Rear - 20mm @ 85°

[WT] Type1 Chi-He

    Today Gaijin gave you all yet another devblog, this time something a bit larger and more powerful than the I-Go. Today's tank marked a new era for Japanese tanks; no longer were armoured units solely for infantry support-- now they were for tank hunting. Today's beast may not have seen the combat she was constructed for, but the capabilities this tank provided would have marked a challenge to its opponents. Today we will take a closer look into the Type1 Chi-He. 

After the results of the Nomonhan Incident (Battle of Khalkhin Gol) of 1939, Japan understood what it meant to face off against a major power. Here they learned a grueling lesson of the challenge posed by combined-arms warfare. The Japanese lost the battle, but their tank corps ended up being successful when put up against the sheer number of Soviet tanks outnumbering them. The Japanese 37mm and 57mm caliber guns proved adequate against the Soviet tank units, which were dealt heavy losses. However, Japan knew they would need to design better units in order to keep up with the rapid development of modern tanks which other nations started introducing. Japan began development of a gun purposed solely for anti tank capabilities, and ended up with a 47mm cannon. The development of the cannon began in the August of 1939, but Japan also knew a new tank chassis would have to be designed to accommodate the 47mm.

Chi-Ha Kai with the Shinhoto turret and 47mm gun. 

In early 1940, the Japanese Technical Bureau began development of a new tank, which was to be named "Chi-He," based off of the Chi-ha. The tank was to focus heavily on increasing the base armour of the original vehicle, as the Chi-Ha was increasingly seen as inadequate in defensive properties. At the time of development, the Japanese military had been testing an experimental tank, the Type99 Chi-Ho, which mounted one of the original turrets designed for the Chi-Ha tank and the test model of the 47mm. The tank never was approved for service, but the turret was selected for further development, and would later become known as the Shinhoto turret. The Japanese needed to produce large quantities of tanks without the reliance of heavy industrial capacity, in order to achieve this the shinhoto turret was selected for use on the already battle proven Chi-Ha chassis. This tank was designated the Chi-Ha Kai, and when the 47mm was completed in 1941. The newly completed Type 1 47mm, the gun was mounted on the Kai model for deployment throughout Japanese territories.

The Chi-He project decided to use the Chi-Ha Kai's shinhoto turret and advance on it. The shinhoto turret was still spasely armoured like the chassis of the Chi-Ha, and lessons learned from the Chi-Ho indicated that welded face-hardened steel was the best way of improving the armor of the tank. This differed to the standard tank construction method of using riveted connection of steel plating. Production of the prototypes began in late 1941, but was delayed due to the successful results the Chi-Ha Kai achieved in the field. It took until September of 1942 for the first prototype to be completed and tested.

The Chi-He Medium tank. 

Development of the Chi-He was assigned to Mitsubishi Heavy Industries, the primary manufacturer of the Chi-Ha medium tank. The tank was characterized by its single flat armour plate at the front, whereas the Chi-Ha had a protruding drivers port with a slight curvature. With the removal of the diver’s armored vision port, the hull of the Chi-He was lengthened by a few centimeters. This enabled the addition of a crew hatch which would have been impossible with the design of the Chi-Ha. The armour plates had a thickness of 50mm at both the upper and lower frontal plates. The Chi-he was given two headlamps on both the right and left fenders as opposed to the Chi-Ha's single center mounted light. On the sides of the Chi-He's hull were two vision slits for the crew inside, in order to improve on the poor visibility offered to the driver by the Chi-ha-Kai. As per requirement of the Army, the Chi-He was to use only singular and straight planes in the design structure. This would increase the overall length of the Chi-He to 5.7 meters, whereas the Chi-Ha Kai remained at 5.5.

Type1 Chi-He captured by the U.S. intel in 1945.

 The turret was kept practically identical to the Kai's, however the turret received bolted armour shielding around the front, giving the turret 50mm of armour in total. The mantlet ring was held together by a riveted 60mm frame. The sides and rear of the turret, however, remained at just 25mm thickness. The crew of the turret increased from 2 to 3, giving the Chi-He a total crew count of 5, opposed to the Chi-Ha's 4. The additional turret crew-member was stationed behind the gunner to the left side of the turret, and was given the task of loading the gun. The additional space provided by the Chi-he’s hull also allowed for stowage of 121 shells as opposed to the Chi-ha’s 101.

Rear view of the Type1 Chi-He.

The tank was also given a new engine that brought a unique feature into the fold. The newly developed Type 100 air-cooled diesel V12 engine achieved 240 horsepower with 2000rpms. The Chi-He achieved speeds of 48 kph on roads and 39 kph offroad.  The engine was an improved model of the Chi-Ha's 170hp SA12200VD. In order to fit, the engine compartment had to lengthened and the sloped upper armour had to be replaced with a flat plate. The rear plating consisted of a vertical upper plate and a sloped lower plate, which were welded together. The total thickness of the rear hull was left with only 25mm.

Chi-He's 15 degrees of gun depression. 

Such changes meant that production of the Chi-He kept being delayed until the development of the tank was completed in 1943. It was only then the Army staff took the tank and tested it against the Chi-Ha Kai. Naturally, the tank outperformed the Kai in all categories. During the tests, the Japanese used a Type96 15cm cannon against the Chi-He. The tank was shot from an angle diagonal to the chassis's right side, and survived the shot. However, the tank's riveted plates were torn apart and the damages were deemed unsalvageable. The welded plates kept intact from the blast. The tank was given the designation Type 1 Chi-He, and was ordered to be produced immediately. However, it was 3 years late and by this time the tank was already outdated compared to the quickly multiplying M4 shermans. The first 5 units rolled out in February of 1944. By the end of the war in 1945, a total of 170 units were manufactured. Despite this number being fairly large for a Japanese production run of the period, the tank never saw combat. This was because the tank was kept at the home island of Japan under the homeland defense act. Here the Japanese kept most late war tanks for preparation of a possible US invasion of the home islands of Japan.

Weight: 15.2 - 17.2t

Crew: 5 men

Length 5.7 m

Height: 2.4 m

Width: 2.3 m

Engine: Mitsubishi Type100

Cylinders: V12 Air cooled Diesel

Power Output: 240 hp/2,000 rpm

Max Speed: 48kmh

Armament: x1 Type1 47mm , x2 Type97 7.7mm MGs

Turret Armour:

Mantlet: 60mm

Front - 25+25 (50mm) @ 78°

Side - 25mm @ 75°

Roof - 10mm

Rear - 25mm @ 90°

Hull Armour:

Front - 50mm @ 72°

Side - 25mm @ 75°

Roof - 10mm 

Rear - 20mm @ 90°

Suspension:

Side - 25mm @ 90° 

Rear - 20mm @ 85°

[WT] Type89 I-Go

 
    Today, Gaijin released their newest devblog, and oh boy is this tank difficult to explain! So, this can probably be blamed on me and my lack of quick response to Gaijin long ago when they asked me to be a consultant for Japanese Tanks and their development. Due to being a busy person I did not have the free time, so they started to work on getting Japanese Ground forces to their players without me, that's only natural. The problem they didn't understand with the I-Go is that the tank has many different models, the naming of which could also be confusing. So without further ado, let's talk about the Type89 I-Go. 

This is the I-Go Ko 1933.

Background

Japan had seen the capabilities of tanks in the military after the First World War erupted. The Great War had illustrated the strategic and tactical transition forced by mechanization and new weapons. These changes frightened the Japanese, who had no major initiatives for armament or organization, and whose doctrine remained unchanged from the Russo-Japanese War, over a decade earlier. Japan decided to purchase a series of tanks from Britain and France in order to initiate their own tank design. With this came a series of Renaults, a Mark.IV Female, and a couple Medium C tanks. In 1927, Japan had constructed their own tank, the Experimental I. This tank was successful and proved Japan could manufacture their own tanks, but the prototype was too complex with too many parts to replicate. Instead Japan decided to use the British medium designs to make a mass production tank.  

Japanese Vickers Medium C, 1927.

In the March of 1927, Japan had also received 3 Vickers Medium C tanks from Britain for additional influence in designing a mass produced tank. Initially, the tanks were favored upon the Japanese until during one trial when the vehicle maneuvered up a hill the excess gasoline exhaust transitioned into the crew compartment and caused an ignition inside the tank, severely wounded two of the crew. In order to prevent future mishaps like this, Japan decided use safer designs such as the diesel engine for their tanks. This took time, all the way up until 1933 for the diesel engine to be designed for their first produced tank on large scale.

After the successful test of the Experimental I tank, the Army developed a sort of boasting confidence that they, too, could produce tanks which could compete with those of other nations. They decided to design two tanks, a light tank of 10 tons, and a heavy of 20. Japan had decided to use tanks to support the infantry in the field, as was commonplace during the period. The light tank was to be produced in large quantities and be able to keep up with the trucks at the time, these would make up the significant force of the tank unit. The heavy tank would be produced in very small numbers and be used as provisional aid in an assault. The 4th Technical Research Group in the March of 1928 began designing a light tank and had finished the initial schematic drawing  in August of the same year. In 1929 the 4th Research group send the plans to the Osaka Arsenal, the facility that built the Experimental I prior, and construction finished in April. The tank was labeled Trial Model No.89 Light Tank.

I-Go prototype during trials, 1929.

The Prototype

In October of 1929, the prototype went through a trial exercise where it drove from Tokyo to Aomori to see how much the tank could handle under long distance pressure. The tank traveled under its own power for a distance of 660km, and was officially recommended for series production by the staff afterwards. The prototype took influence from the Medium C and its flaws, the tank used a remodeled and simplified version of the C's suspension design, with 4 pairs of roadwheels connected by a set of bogies and semi-elliptical spring placements, a ninth roadwheel placed in front of the forward road wheel in order to achieve superior climbing and trenching capabilities. This was a major improvement over the Vickers C, which was not capable of handling steep inclines and damaged the vehicle as a result. The tank had five return rollers, rear driving sprocket, and a forward idler wheel. The tank used a 6mm cover protecting the suspension system. This was mainly designed to prevent Chinese and Soviet infantry from damaging the complicated and high maintenance suspension in combat. The frontal armour of the prototype was divided, with the upper 1/4 mounted with vertical plating and the lower 3/4 sloped. On the bottom plate in the front, a crew hatch was implemented to the right of the tank where the machine gunner was seated.

Prototype as seen in the side profile. 

The prototype used a licensed built 6 cylinder Daimler water cooled gasoline aircraft engine with an output 100hp, which was located to the right in the rear of the chassis. It was accessed with a small hatch from the crew compartment. It was supported by an 180ah battery to give enough power to start the ignition. Gasoline tanks were placed on the sides on the plate above the suspension, the oil tank being placed left of the engine.

In the crew compartment the driver was located left of the tank (looking forward, not at) behind visor port. The MG gunner sat to the right operating a Type3 light machine gun mounted behind the front armour plate. Several ammunition boxes were placed on the right of the bow gunner, adding up to 2800 machine gun cartridges. To the right and left of the tank contained small boxes of rounds for the primary gun, 110 shells.  Similar to the design of the Experimental I, the turret was a slight conical shape but had a protruding extension to the drivers side that contained a second Type3 light machine gun, 180 degrees apart. To the left of the MG was the rear turret hatch for tank commander to use when needed. The commander of the tank acted as the primary gunner and loader, while the second turret crew was stationed at the MG at the rear of the turret. The primary gun was a Vickers 57mm due to the Type90 57mm still being developed for the tank series.

Pre-Production

The prototype was accepted and in late 1929 the tank entered service with the military. It was designated the Type89 I-Go medium tank. The tank gun was finished in 1930, however production numbers of the gun were minimal and could not be iterated on the first production tanks completed. As a result, the first I-Go tanks mounted a 37mm Sogekiho Infantry cannon. This model of the tank was very rare.

First I-Go tanks had a 37mm gun, divided front plate,
vertical cupola, and two headlamps. Did not have
tail. 

These 37mm I-Go tanks were only produced with 5 units, and only saw combat on February 1932, Shanghai. After the results of the Manchurian Incident, Japan and China had broken out fighting in Shanghai. The I-Go tanks were placed in the 2nd Independent Tank Company, accompanied by 10 Renault tanks. It was here the Japanese knew that their tanks needed tails for trenching and gap crossing due to the nature of the city's layout. This proved to be the first combat scenario the Japanese were met with that had both sides shooting one another, so the crews of these tanks were interviewed after the battle had ended.

The tanks performance was satisfactory, but many changes were recommended. The tank did not have a mantlet, this created a noticeable gap when the tank gun when elevated, allowing Chinese infantry to shoot the tank crew. In order to fix this issue the tank was given a small box shield in the next version of the tank. The armour of the initial tanks was divided by a sloped underside and a vertical front. This was met with challenge as Chinese infantry guns that targeted the sloped underside bounced and often hit the center hull, causing disruptions. This too was changed in the Kou model with an all vertical plate. These changes would be made starting in 1933.

First Production

 First iteration I-Go Kou. 

The first production models were issued with the completion of the Type90 57mm, and production of this series of the vehicle began in 1931. This variant was labeled as the Type89 I-Go Kou. The tank was produced right after the 5 37mm models and formally entered service later that year. The first production model of the I-Go mounted a water cooled gasoline engine, though the front plate was still composed of the same two-part angular lower glacis and flat upper glacis. The I-Go Kou otherwise kept the design of the pre-production model and used a vertical cylindrical observation tower with 4 slits for viewing. Instead of a single turret hatch on the top, the tank was given two hatches, one on the left, and one on the right. The right hatch was under the cupola tower. The tank kept the traditional suspension system of the prototype, however it was changed by removing the track hooks on the pre production model. This was the last model to feature two-part crew hatches in the front of the vehicle. Additionally, the 1932 model of the I-Go Kou would be given shorter track links made of better steel to reduce overall track wear and provide better maneuverability in rough terrain.  

Second Production Model 

In 1933, additional improvements were typed into an official second model; rather than retain the flat upper glacis, the I-Go’s frontal armor was reshaped into a single sloped piece, mounted on the front mud guards. This single piece was riveted, and featured additional armor on the front hatches.

Early 1933 iteration. 

To add to the confusion of identifying the various models of the Type89, many of the second production models retained the turret of the first production model and its cylindrical cupola. This was largely a matter of convenience: Japan’s production capacity was limited, so there was an impetus to use whatever was available. Eventually, all models produced in 1933-1934 were produced with the new mushroom-shaped cupola that replaced the older conical observational port. While these improvements were officially introduced in 1932, they are mostly identified with the later 1933 and 1934 models. Otherwise, the second production model still maintained the water cooled
gasoline engine. It was the least-produced out of all
the Type 89 variants.

Late 1933 iteration. (This is the model Gaijin has for War Thunder. )

Third Production Model

Starting in 1934, the tank used a new suspension type in order to improve mobility. The drive sprocket was moved forward by 50cm (10in) in order to increase the traction control; the suspension mounting position was lowered by 15 cm, thus raising the hull further off of the ground. The number of upper return rollers was decreased from 5 to 4. The upper track roller support frame was removed, and the upper track wheel was changed to a cantilever style suspension mechanism. This model kept the same engine, but had a new crew placement of the driver on the left, and the MG gunner on the right. The turret was given a rangefinder, and the armor was improved slightly. An additional battery storage compartment was mounted on the upper hull, since the ignition motor had been improved and now required more power. Accordingly, an inspection door was installed on the upper surface of the rear portion of the vehicle body. The exhaust port of the muffler was changed to a cylindrical shape.

Third production model (1934) of the I-Go Kou. 

The late models of this tank

also mirrored the crew positions.

Prior to the late 1934 production models, the driver was located  in the right side of the tank (looking from crew perspective), and the Mg gunner was on the left with its own access hatch. With this third iteration of the tank, the crew swapped places. The hatch was located on the right along with the MG position. The driver was moved to the left.

Final Production Model - Otsu 

The last model of the I-Go was not called Kou. Japanese engineers had originally intended to mount a diesel engine in the original prototype for safety purposes and easier field maintenance. However, Japan had neither the experience or tools necessary to produce such engines when the original model was fielded. Only in 1935 were the first diesel engines completed and ready for use in the Type89 I-Go. The tank remained almost identical to the late 1934 model Kou, With this new engine, the radiator that had taken up the left side of the engine compartment became unnecessary. As such, the fuel tanks which were once mounted on the left and right sides of the hull were moved into the space vacated by the radiator. Production of this model began in 1934, but it did not enter serial production until 1935.

I-Go Otsu

To free up additional space, the battery and oil containers that were in the engine room on both sides of the tank were transitioned to the sides of the vehicle. Fuel replenishment pallets were installed on the right upper surface of the tank. One lubricating oil supply pallet was installed on the upper rear of the tank. The armor grill over the radiator was changed to a hinged design which opened to the left. This gave access to a siccoro fan which pulled air through a pipe and into the diesel engine itself. The battery inspection door in the center of the rear slope of the tank chassis was also enlarged. Since the vehicle no longer used an aircraft engine the water-tank lid and the lubricant supply lid for the radiator, which were located on the upper surface of the rear part of the tank, were removed. Also removed were the carburetor and its service hatch, while the muffler was changed to a triangular design.

Believe it or not, but this is only going over the official production models. The I-Go underwent many, many field modifications. Keep in mind two tanks may be the same model yet have small differences. This is because two corporations took part in producing the I-Go, Mitsubishi Heavy Industries and Tokyo Manufacturing Plant. Both were new factories, both had their own unique appearance of the I-Go Kou tanks. Besides this, there were other variants down the line. This is why the tank is very, very complex.

Japan's First Tank

As the First World War was coming to a close, major powers across the globe began to design and manufacture tanks, realizing the potential of the new metal beasts. Armoured warfare had entered the world stage and countries began creating their own interpretations on what they envisioned as being a tank, and Japan was no exception. Japan was mainly a spectator during the war, but the Japanese Army had obtained information from closely watching the tanks deployed by the British and French. The Great War had illustrated the strategic and tactical transition forced by mechanization and new weapons. These changes frightened the Japanese, who had no major initiatives for armament or organization, and whose doctrine remained unchanged from the Russo-Japanese War, over a decade earlier. Japan thus realized they needed to modernize with the rest of the world, and in 1917, the Imperial Japanese Military Motor Vehicle Investigation Committee dispatched Captain Mizutani Yoshiho to the United Kingdom to purchase a Mark.IV Female tank for research in Japan. Thus, Japan’s first tank would arrive in Yokohama port on October 24, 1918. Japan had also purchased 22 French Renault FT-17 and 4 British Whippet tanks, which were imported to Japan in 1920.

Tomio Hara.

 In 1925, the Japanese decided to start producing tanks of their own. The Army Staff had initially planned to obtain licenses to build British and French tank designs, which they knew would work as they were tested and put into service successfully in World War 1. These were to be used solely as infantry support vehicles due to the lack of proper infrastructure, qualified engineers, and mechanized personnel. This initial plan was not agreed upon by everyone, however. Tomio Hara, a relatively unknown engineer from the Army Technical Bureau, envisioned that tanks would become a staple for the military, have their own doctrine, and even have their own separate branch of the military. Hara was outspoken, and his opinions clashed with those rest of the team he was part of; he was ambitious while the rest of his team favored implementations which preserved longstanding military traditions. The Operational Chief of Staff gave the Bureau the task of drawing a design Japan could use. The tank was kept under strict limitations, such as a maximum weight of 20t, so that it could compete with other modern nations’ tanks. To top it off, they were only given a period of 2 years to do so. This may not have seemed difficult, because tank development worldwide in 1925 was minimal. The Army Staff had thought it would be impossible and gave the team free reign to do whatever needed to be done besides the vague requirements. However, Tomio Hara (Head of the project) assembled his own team of 16 engineers and they began designing their own tank. The Army Staff had given them the order to do so in February of 1925, and he and his team went right to work. 

Photograph of the Mark.IV Female tank at the Chiba Infantry School in 1918.

The Technical Bureau had confidence that they could meet the Army Staff's requirements and show that they could successfully design and make their own tank. Until this point, the engineering divisions had only designed small vehicles such as a 3 ton towing car and a 4 ton automatic tractor that had a maximum speed of 24kmh when tested. However, the initial characteristics of the tank were as followed;

“The total weight kept around 12/15 tons occupying a crew of 5, a total length of 6 meters, the dimension of which would not hinder the placement on railway transport. The armor capable of withstanding an oblique shot of a 37mm infantry gun, from 500-600 meters. Supported by a central rotating turret housing a 57mm caliber primary cannon, two machine guns placed in a front and rear separate turret; an engine output of 120 horsepower with a maximum speed of 25 kmh, trench crossing ability of 2.5 meters with climbing radius of 43° degrees.” 

Type90 57mm anti tank gun.
The gun used on the Ex.1 was
an early version of this.  

The tank design was later given more specific requirements as development progressed. The internal structure of the tank was divided into 3 sections; a front crew compartment, an engine housing, and a rear crew compartment. This matched with the turret setup of having two turrets in the front and one in the rear. These compartments were separated by 6mm thick armor plates, with doors to allow traffic through to each compartment. The central turret was provided with an observational window which could be traversed individually of the turret itself. The vehicle was to be given a 8 cylinder engine with an output of 120hp, and a transmission with 6 forward and 2 rear gears, allowing a maximum speed of 20kmh. The engine was unique in the sense it was both air and water cooled. The engine room itself was located in the center. A hatch from the front and rear led into the compartment. To the left and right sides of this compartment were carefully placed containers for the gasoline and oil tanks, and a combined exhaust pipe located to the right of the tank that led to the muffler on the rear. The steering system should be able to turn the pendulum using a constant ratio transmission equipped with a planetary gear box, and have a turning radius of 7 meters. A parallelogram suspension design was chosen and was to be protected by an armoured mud shield. The tracks were supported by 8 paired road wheels at the bottom of the suspension and three individual support road wheels for providing hillside climbing capabilities and maintain stability on whichever side traversing upward. In addition to that, five return rollers with the first one raised, a forward idler wheel and a rear driving sprocket were used. 

The design was finished in May of 1926. Japan's domestic automobile industry at the time was extremely minuscule, poorly developed, and was also crippled by the fact that few factories in the country owned proper machines and tooling for the manufacturing of large parts for automobiles. To counter this, the Technical Bureau knew that they had to build the parts one by one with their own resources, in small dimensions. This would be done at the Osaka Arsenal, the primary facility for the Army at the time. Mitsubishi and Kawasaki both aided in building many of the parts for the tank. Around this time Mitsubishi was divided to have a Naval and Aerial division. The company formed Mitsubishi Heavy Industries shortly prior to the Experimental I's construction. The design that the group came up with exceeded more than 10,000 individual pieces.

The Experimental I tank. This single prototype proved to a nation that they were capable of designing their own tanks despite only modernizing recently. 

The prototype was completed in February of 1927, two months before the expiration date of the project. The engine output was distributed and operated by a steering transmission incorporating a planetary gear unit. This was designed and patented by Hara himself. It had the function of a constant radius and pivoting turn plus emergency case deceleration of its main brake. Compared to the clutch brake style, the power loss is minimal and it became the standard system of Japanese tanks onwards. The tanks turn radius was only 4.6 meters and it was possible to turn the vehicle by moving only the crawler belt on one side of the vehicle. The suspension was arranged in a method of a bunch of small rolling wheels guided by a sprocket on the front of the hull and the ignition wheel behind it. It's coupled with a large shock absorber holding a large bow shaped spring and a connecting rod which moved independently and was attached at each end. A small rolling wheel was connected to this. The armour plating used on the prototype was formed using mild steel. This was due to the lack of bulletproof steel that was not yet widely distributed for tanks and welding was not developed in Japan or in general. Rivets were the primary style of constructing tanks and other armoured vehicles at the time. 
 

The first demonstration was held near the base of Mt. Fuji on June 21st, three months after the Experimental I finished construction. It was an inspection test where preliminary testing was not carried out within the Army Technology Headquarters. After being transported by train from Osaka, this tank drove about 8km from Gotemba Station to the Army barracks while military officials and the general public were spectating. Naturally, this was a risky thing to do as the tank was just a prototype and was prone to breakdowns and failures. Reliability was minimal but it showed Japan's staff, military, and even its people that a new age had begun for Japan.

Experimental I being shown publicly at the Tokyo Showing. 

Subsequently, a trial test was conducted at the Fuji Exercise Station, easily going over a steep slope, and accomplished the traversing of levees and trenches as placed ahead. The Experimental I showed much more mobility than tanks from Britain and France had been, and the tank kept a solid stability level for shooting exercises. During the trials, Tomio Hara made the comment "...... In the eyes of those familiar to us with foreign medium tanks going 14 kilometers an hour, the appearance of an 18 ton tank going over 20 kilometers and hour rushing up the road is spectacular in itself. Adding tank power to our nation's defense? I have a sense of trust. ".

At the time, there was no precedent for the Army, tanks were not a thing of familiar nature. Hara and the rest of the Bureau proved to the Army Staff that Japan was capable of successfully designing a tank. Even the individuals who were against tank production were now all for it. The trials of the tank were very successful, but the tank was never adopted into military service. The problem with the Experimental I was that the Army's weight requirement was 12 tons, the weight of the tank in the design phase was 16 tons, and it weighed 18 tons when completed due to reinforcement of each part with the build prototype itself. The tank only had a maximum speed of 20kmh, despite the requirement for a 25kmh max speed in order to move along with infantry. At that time, this was considered to be a problem for the Army which had imagined a conflict with the Soviet Union, planning to operate tanks in the vast plains of Northern China. This tank did lead to the accumulation of valuable domestic tank development experience, and it would be used for decades to come.

[WT] ST-A1

Greetings everyone! Many community members were concerned of whether they would ever get word on a Japanese tank that wasn't a Tier 1 or 2. Well, today Gaijin has answered your question, and now we get a look at Japan's first post war tank. I have written the devblog on this one (and will continue to), and have already written a previous article on its history. So, today's overview will be a tad shorter. Anyhow, let's take a deep look into one of Japan's first postwar tanks, the ST-A1.

Many will notice how small the turret is. Yes, this is an error in the model. It'll most likely get changed for you by release. 

In the years following after the Second World War, the Japanese were heavily restricted in their military. They were limited to a Police Force in 1950, and by 1954 they were permitted to form a National Defense Force with the sole purpose of maintaining their borders without relying on the United States Military. This action was detailed and enacted through the U.S and Japan Mutual Defense Assistance Agreement. With the tensions between the Communist’s and the free world simmering up, the Japanese knew that at some point, they too would need their own tanks. Until then they had been using leased Sherman, Bulldog, and Chaffee tanks in their arsenal.

A year after the Japanese Self Defense Force was formed, development on their first tank began with two vehicle requirements: one for a main battle tank and one for a tank destroyer. The tank destroyer was given the designation SS, and would eventually be produced as the Type60 Tank Destroyer, known for it’s twin recoilless rifles. The battle tank was designated ST-A (Short for Special Purpose Vehicle A), and was to use the M47 / M48's 90mm as inspiration for the design of the vehicle’s main armament. This became official in 1955, when the U.S Military and the Japanese agreed to aid one another in technological advancements. Originally, the design of the vehicle was to be 25t, but Japan soon understand that the tank needed to weigh in at least 30t to be given necessary armour protection. The contract to build the tank was licensed to Mitsubishi Heavy Industries, which had a large role in the manufacturing of tanks for the Imperial Japanese Army and Navy throughout the duration of World War 2.

By October, both tank ideas were produced in mock-up form. The finalized weights they came to were 32t and 35t vehicles respectively. Despite the original requirement of a lightweight tank design, the General Staff Office were pleased with what Mitsubishi had shown, even though it had increased the final weight to 35 tons. Both designs were presented at the 5th Technical Council in 1955. The names given to these tanks were ST-AI and ST-AII. After the presentation, the JGSDF ordered a 32t prototype mock-up and further studies. The prototypes were completed in October of 1956. The weight of the ST-A1 was 34 tons, 8.59 meters long (6.6 meters body length), 2.9 meters wide, and 2.23 meters tall.

ST-A1.

The design of the tank emphasized its low silhouette. The ST-A1 followed the original order in this regard, as the Ground Staff Office wanted a tank low to the ground which would give anti-tank missiles a more difficult time getting a proper shot on the vehicle. However, this also meant that the vehicle could not traverse its turret fully to the rear without elevating the cannon. Hence, the length of the tank had to be extended to avoid further issues. The suspension wheels became narrower as the track length extended. This increased the ground pressure, which caused problems traversing. The tank's width was kept under 3 meters in order to properly fit on railway cars that would be used for ease of transportation.

The transmission of the ST-A1 was designed to use an automatic style clutch with a torque converter. A power-steered rear wheel drive system connecting straight to the engine and transmission to the rear was also planned, like what other modern tanks in the West used. Overall, this design was not used on the prototype. There were no problems with technology that the Japanese SDF had, therefore they did not need parts that the U.S was using. Initially, the prototype ST-A1 introduced a two-stage torque converter manufactured by Sweden's SRM Company, however when it was installed, there were problems with power loss and agility, which was not a satisfying appearance to the Council and their requirements. Instead, a front wheel drive system and a constantly interchanged gear-style transmission were chosen. A normal manual transmission of the 5 forward and 1 reverse speed was used for the ST-A1 prototype. It had an air-cooled diesel engine and torsion bar suspension. The tank was to use a custom made engine, but due to an incoming deadline, the tank prototype mounted the Mitsubishi DL10T V12 liquid-cooled diesel engine with 500hp at 2,000rpm instead. The max speed of the tank on off-road terrain was 45kmh.

The gun selection on the ST-A tanks was fairly straightforward. The Japanese wanted to use the American's new 90mm tank gun as the staple for these prototypes and for the production model as well. The Japanese were never able to obtain a license for the 90mm M3, however they were given permission to copy the design to the best of their own abilities. The 90mm Japan came up with was left unnamed until 1961 when the Type61 Main Battle Tank was serviced, to which then it became the Type61 90mm Anti Tank Cannon. By this point the cannon was given heavy modifications to the original one used on the prototype model. However the same name was applied accordingly.

 When the Soviet union released their new and modern T-54 tank, the Japanese Self Defense Force considered designing a larger 105mm cannon to deal with this tank. However, due to finances and time shortaging, the gun never left drawing boards. Instead, Japan focused on modernizing their 90mm. 

ST-A1 Prototype. December 1956. 

The cannon had a elevation of +13 degrees, which can be seen as poor for most Japanese tanks. However the depression of the cannon was capped at -10 degrees. The muzzle velocity of the cannon’s shells was 830m/s for high explosive shells and 910m/s for armor piercing shells. The cannon had a rate-of-fire of 10-15 shells per minute, and a maximum target range of 13,060 meters. Turret rotation speed was 24 degrees per second, and cannon elevation / depression was 4 degrees per second.

In the end, the ST-A1 did not meet the proper requirements of the Ground Staff, and the ST-A2 was chosen for further development. However the ST-A1 represented the first time since the Second World War that Japan had designed and manufactured their own indigenous tank and presented it globally.

 I have written an article covering the entire story of the post war tank development in my prior article, Fresh Start, New Beginnings. The tank's detail are kept minimal, the story behind the other prototypes are where the history starts getting into the specifics. 

Weight: 34t

Crew: 4  

Length 6.6 m (Hull) 8.59 (Including cannon)

Height: 2.23  m

Width: 2.9 m

Engine: Mitsubishi DL10T V12  

Cylinders: V12 liquid-cooled diesel

Power Output: 500hp/2,000 rpm

Max Speed: 45.2kmh

Armament: x1 90mm (Eventually Type61 90mm) , x1 12.7mm M2 Browning machine gun

Turret Armour:

Mantlet: 124mm

Front - 75mm

Side - 40mm

Roof - 18mm

Rear - 35mm

Hull Armour:

Front - 45mm (Effective 75mm)

Side  - 25mm

Roof - 25+25mm

Rear - 20mm