Thursday, February 16, 2017

Development of the Modern SPAAG

  As the Korean War began and tensions escalated in Asia, the United States began to supply the Japanese in the event that they would need military aid or a form of protection against the rise of the communist states in the region. The United States had already began developing their own new and improved combat vehicles for similar purposes. Because of this, they were left a large surplus of outdated military vehicles and no where to use them effectively. Hence, many were later donated to the Japanese for them to use in training new troops. The Japanese Self Defense Force was created in 1954, allowing the Japanese to have their own defensive military to protect the home island when needed. During this period, the United States had officially decommissioned the M19 Gun Motor Carriage SPAA vehicle from service. These were anti air tanks based off the M24 Chaffee chassis, and mounted twin 40mm Bofors multipurpose guns. A few of them were supplied alongside the M42 Duster.

These lend lease tanks were short lived, however. During their initial time spent in the SDF, they were used as trainers for anti air tactics and methods of engagement. Even for the Japanese Self Defense Force, the short ranged 40mm Bofors guns were inadequate and couldn't meet the requirements needed to successfully engage and destroy modern aircraft of the era. These concerns were voiced to the United States over the years ,however the US simply ignored these requests as well as Japanese requests for modern armor. Faced with the refusal of the US to supply more modern vehicles, the Japanese decided to initiate their own SPAAG program during the late 60's.

The First Prototypes
In the late 1960s the the Technical Research Department came together to conceptualize a new SPAA-like vehicle to meet the needs of the military. Their logical conclusion was to use the chassis of the Type 61 main battle tank as the starting point. While the tank was a failure to the military, the use of its chassis  for an anti aircraft tank could have given it a new lease on life; Japan had already started working on a new main battle tank project to replace it, and the choice seemed to be the best use of resources at the time.

M51 at Chiba, Japan. I have yet to receive visual details
from the SDF on the prototype vehicle. I am currently
awaiting access to the details. 
The research staff concluded instead of designing its own anti aircraft gun, it would also rely on the technology the United States left behind with the lending program. The gun they had in mind was the M51 Skysweeper, a 75mm anti aircraft system and one of the first to utilize an automated targeting system with an auxiliary predictor and gun laying radar stations in one platform. The gun relied on an autoloading mechanism with two 5 shell belts. The gun had proved to be very useful during its time, albeit fairly outdated during the 70's. Nonetheless, it was selected to be used as the candidate armament.

The first prototype was completed  in 1972, and was put through various trials. Ultimately, it was rejected by the Self Defense Force for its turret being "excessive" and unreliable. Due to this unwanted outcome, the project for a new SPAAG was canceled. No attempt  to find a suitable replacement would be attempted for six years. In 1978 the decision was made to again attempt to base a new SPAAG off the Type 61 main battle tank chassis. The Japanese Self Defense Force worked out a cooperation agreement with Oerlikon Contraves, a renowned anti aircraft gun manufacturer of the era. Oerlikon provided Japan with a design proposal for a set of 35mm autocannons on a rotatable turret design which would house a search and track radar.

The second prototype of the SPAA project. Mounting the new twin 35mm autocannon system into the Type61 chassis. It was labeled the AWX. 

Various tests were carried out using the completed prototype vehicle. It had became clear that the combined weight of the turret, radar, and computer systems was too heavy to allow the vehicle to maintain the desired level of mobility. The prototype was canceled. Instead, the hull of the newer Type74 main battle tank would be used as the chassis for the new SPAAG. The original Type 61 prototype would eventually be converted to a bridge-laying vehicle in the 80s.

The Guntank

Development and trial production of a self-propelled rapid-firing aircraft gun vehicle based off of the Type 74 MBT would begin in 1982; one set of two prototype hulls was ordered in that year. A third hull was procured in1983. The first prototype was completed at the end of 1983, and technical tests were conducted from 1984 to 1985. A practical test by the Ground Self Defense Force was carried out in 1986, and it was formulated as '87 self-propelled gun' on August 21, 1987.

National Defense Agency File H 4001B 1 &2
To save weight and avoid the flaws of the original Type 61 derivative, the turret of the Type 87 was made with a lighter composite. The replacement was the AMS 4050A Specialized aluminum alloy. A complex alloy of bulletproof materials that offered decent protection for its weight. It could not defend against dedicated anti-tank weapons, however.

The turret of Type 87 was developed by Japan Steel Works, with the radar and fire-control systems housed in a boxy structure which gives the turret a distinctive shape similar to that of the German Gepard.  The similarly is furthered by the fact that both tanks have their 35mm autocannons on the right and left sides of the turret. The variety of ammunition used for the 35mm autocannons is extensive. HEI (535g) is used for targeting general aircraft. The guns also use SAPHEI (380g) for ground targets, and APDS for armoured targets. The APDS rounds have a penetration capability of 40mm RHA at 1000 meters (at 60 degrees slope) distance with a muzzle initial velocity of 1,385 m / sec.

The 35mm's drastic gun elevation can be seen
here during this SDF exercise. 
The gun barrel is an air-cooled type, and six grooves are engraved on the outer circumference to increase the surface area and enhance the cooling efficiency. The rate of fire of 35 mm high fire aircraft gun KDA equipped on the Type87 is around 1,100 shots per minute with the gun elevation angle of  -5 to +85 degrees. The turret can rotate a full 360 degrees with no impediments. The turret and cannons are by default operated electronically, however they can also be operated manually if the need arises. The gun's elevation speed is 760 mils / second, and the turret's traverse speed is 1,000 mils / second. The turret is also equipped with two sets of smoke launchers to offer a base of protection if under threat of engagement from the ground and air, similar to the Gepard.

The detection range of the Type 87's laser detector was 360 degrees in a horizontal direction and -22.5 degrees to +90 degrees vertically. The Mitsubishi Electric Corporation was in charge of development of the tank's systems. The detection radar antenna was located to the rear of the turret, posted as a long protruding object, boasting a detection range of 20 kilometers.  The search radar antenna can continuously turn 360 degrees, and the turning speed of the antenna is 30 rpm. The dish type equipped on the top of the turret in front of the search radar antenna is a tracking radar antenna and the tracking range is said to be 20 km. The tracking radar antenna can continuously turn 360 degrees, and the range of elevation is -80 to +1, 500 mils. The turning speed of the antenna is 1,600 mils per second, and the elevation speed is 890 mils per second.

During the late 80s, Japan began to test the protection capability of composite armour. The new STC project was at the forefront of development. The Type74 had been tested with examples of composite, as was the Type87. The prototype adjusted to this by adding two spaced armour pads while the chassis remained produced in steel. The front hull was only protected by a thin 33mm RHA plate.

National Defense Agency
File H4002C 1
Although the chassis of the Type87 is a welded structure of rolled homogeneous steel based on the Type74 battle tank, the shape and composition  have been changed drastically to the point where only a few similarities remain between the two vehicles. The front plate has since adopted a method of composite armour inside the front hull of the vehicle, instead of the externally placed pockets on the prototype. The front hull remained 33mm thick, whilst behind the plate a formulation of internal fins adjustably angled, made up of mostly NERA (Non-Explosive Reactive Armour). The method used is similar to American and German designs,  which used this method of protection on the sides of their tanks, effectively defeating light guns and autocannons of the 30-50mm range.  For the Type87 this method proved adequate for its anti aircraft role.

There was a downside, however. The complexity of the armour and the technology of its turret raised the price of the vehicle to over 1.4 billion yen per unit. Due to this steep price, the SDF was forced to only produce 1-2 units a year. The series production ran until 2002, where by this time a total of 52 units were manufactured and in service. The tank remains in SDF operation to this day. Because of this, many specifications and details are considered classified. This leaves much to be questioned in terms of the secrets under the armour.

The Type87 retained the excellent mobility of the modified Type74 chassis. The tank was equipped with a Mitsubishi Heavy Industries built Type 5 10ZF22WT two-stroke 10 cylinder air-cooled turbocharged diesel engine. It was capable of forward speeds of 53 km/h with an output of 720hp at 2200 rpms. Since the suspension of the Type87 was directly copied from the Type74, the vehicle could control the hydro pneumatic movement of the chassis in the forward, backward, side to side, and up and down motions to varying degrees. While tactically useful for the type74, the Type87's suspension had acted more for novelty than anything else.

The auxiliary power unit for the tank is located to the tank's right frontal side. This station provides electrical power for the tank's fire control computer, search and tracking radar, and turret drive generator. The APU is powered by a four stroke diesel engine with 29 liters of displacement and 75hp with a 2850rpm output. It is visible through the heat exhaust panels.

I know this is a long post, but I wanted to write a brief rundown of Japanese anti aircraft tanks after the world war. It's a very complex history and I wanted to summarize it for you readers in the best fashion possible. The SDF has been kind enough to share such snipbits, and today I used information from two files belonging to the National Defense Agency. The first being H 4001B 1 &2, and second  H4002C 1.

Monday, February 13, 2017

The Tigers of Corregidor

One of the longest standing myths regarding Japanese tanks was the infamous "Tiger of Corregidor ". How come a lone Type 97 Chi-Ha was able to defeat nearly 40 American M3 Stuarts and allow the Japanese victory over the island of Corregidor? Today I want to end such myths as I go over the historical events of the engagement that led to the American's surrender of the Philippines.

Fall of Luzon 

   As the war in the Pacific took a turn for the worst, with the United States declaring war on the Empire of Japan on the 8th of December 1941, the Japanese high command realized they would need to act in haste after their unexpected attack on Pearl Harbour. During the month prior, the Japanese high command had created the Southern Expeditionary Force, so as to engage in the territorial capturing of various islands of Southeast Asia. Their first target was the Philippines under the protection of the United States. The final plan of engagement had been adopted in mid-November. On the same day as the declaration of war, the Japanese 14th Army, under the command of Lieutenant General Masaharu Homma, had embarked from Taiwan and landed on Batan Island. On the 10th of December, the 14th successfully occupied the Port of Aparri on Luzon and began advancing further south. The 16th Division landed on southern Luzon to force the capitulation American General Wainwright's defense forces with the aid of the 14th from the north.

 Lt. Morin's Captured M3 Stuart on Luzon. 
General Wainwright had received information that the Japanese 4th Tank Regiment, commanded by Lieut. Colonel Kumagaya, was approaching his lines of defense. The General ordered Captain Hanes of the 192nd Tank Battalion to engage the mechanized forces of the Japanese in the town of Damortis. However, Hanes’ M3 Start's force was nearly out of fuel at the time. Because of this, he ordered lieutenant Ben Morin to command a platoon of 5 Stuart tanks to engage the Japanese assault. On December 22nd, the 192nd and the 4th met in combat, however the Japanese were expecting the lieutenant's force and staged an ambush for the oncoming platoon. Once the 192nd had sight on the Japanese Type 95 Ha-Go’s, Morin's Stuart immediately broke formation to meet the tanks head on but was crippled with a hit to the engine, setting the tank on fire. The remaining four Stuarts were taken by surprise and damaged severely, but managed to escape the battle. Ben Morin and his crew were able to survive, however they were captured as prisoners of war by the 4th Tank Regiment. As a result, the M3 Stuart belonging to Morin was captured and repaired to be serviced by the 4th, later to be commanded by the 7th Tank Regiment.

As the American forces retreated further into Bataan’s interior they were able to receive effective air cover, preventing the Japanese advances through the Subic bay area. This allowed General Wainwright to secure a foothold in the region while the Japanese spent the 1st through the 14th of January formulating a new battle-plan. The fighting resumed on January 23rd, and lasted just two weeks before Lieutenant General Masaharu Homma withheld further attacks due to casualties on the 8th of February. Once reorganized fully, the Japanese 14th Army during March began pushing once more against the American and 57th and 45th Infantry, coupled with the Philippine 31st Division along the Alangan River. The Allied forces could not sustain engagements with the Japanese, and were forced to surrender deeper to Corregidor Island.

Landing on Corregidor 

To Japan, the island of Corregidor was of the utmost importance to the war effort; its position ultimately decided who owned Manila Bay, a strategic location in south-east of the Pacific. Beginning in early February, Japanese airstrikes targeted the island in an effort to cripple American fortifications there. While major damage was inflicted on Corregidor, the morale of the US soldiers remained high. Unlike the Japanese,however, the Americans were not used to combat and were unable to accurately hit Japanese targets in the air and ground with their coastal artillery. Because of this, Major General Kureo Taniguchi decided to strike with a landing force immediately in first week of May. Using a force comprised of 790 infantrymen and supporting armor, the Japanese attacked at midnight on the island fortress. However because of Taniguchi's lack of planning, the first landing force met stiff resistance as they were blown off course by strong winds, and struggled to get a foothold on the beach. With this temporary setback, American troops were able to inflict heavy casualties on the Japanese until they were able to reorganize. The landing succeeded largely due to the overwhelming Japanese advantage in numbers, but would come at high cost; the second landing force was almost entirely destroyed when strong winds carried it into range of US machine-guns.

Tanks on Corregidor
Tsuchida's Chi-Ha Kai on Corregidor.
Since the 4th Tank Regiment was kept on Luzon and Manila, the 7th Tank Regiment had been ordered to remain on hold at Limay in Bataan. The 7th were tasked to support the Japanese strike on Corregidor island alongside General Kureo Taniguchi. The 7th Tank Regiment was originally under the command of Colonel Sonada, an officer who took part with the Tank Research Committee and Ministry of the Army. He sought to utilize Japan's newest weapon, the Chi-Ha Kai, a new tank produced by the Japanese to better engage in tank combat against the Americans. The 7th regiment was equipped with two such vehicles during the invasion, the first such deployment prior to the vehicle’s official acceptance into IJA service. The deployment of these vehicles was relatively inauspicious, however; Colonel Sonada was killed in battle during the capture of Bataan in April, so the regiment fell under new command of Major Matsuoka, who promptly fell ill with dengue fever.This left the 7th Tank Regiment without a commander. Temporary command of the regiment was given to an officer by the name of Masuda while Major Matsuoka recovered. However, shortly after the battle Major Matsuoka passed away due to the severity of the fever.

When the landings took place at 11:00 PM on a stretch of land between Cavalry and North points, the 7th sent a platoon comprised of the two Chi-Ha Kai tanks and the captured M3 Stuart with the first landing force. Commanders Tsuchida, Takahisa, and Ho were assigned to the three tanks. Ho was commanding the Stuart, while Tsuchida and Takahisa led the Chi-Ha Kai tanks. The presence of Japanese tanks proved effective in boosting the morale of the assaulting infantry they accompanied, and led them to continue assaulting the beaches of Corregidor. Japanese tanks could not account for the weather, however; the 7th’s second tank platoon, which was landing with the second wave of infantry, were blown off course by a storm. Caught in American spotlights, they were destroyed when their transports were sunk by US and Filipino 37mm guns. The crews of the vehicles survived, however, and swam to shore with the rest of the landing troops until they were sent back to Bataan the following day. The remaining forces cleared the beach of American troops by 2:30 AM.

Earning the Title
    In spite of the landing’s overall success, the three remaining tanks met with significant challenge. The exit from the landing beach was blocked by a large 50 meter hill near Denver Battery, with many large rocks and rough terrain discouraging easy passage. The Chi-ha Kais commanded by Tsuchida and Takahisa attempted to climb the hill, but met with little success thanks to teething problems and a lack of engine power. Eventually, the M3 Stuart under Commander Ho towed the two Chi-ha Kais up the hill. It was not until 8:30 in the morning that the tanks were able to completely climb the hill. Later that day, the Japanese advance was halted by American infantry counter-attacking from Denver Point on the island's plateau. Caught by surprise, the Japanese took many infantry casualties, and were pinned down by a pillbox to the right of the main axis of Japanese advance. The troops informed Commander Tsuchida of the pillbox to their right, and the Chi-Ha Kai was able to destroy it after a successful first shot, allowing the advance to continue. Commander Ho took his Stuart to move up to the right of the advance to support the infantry.

Tsuchida's Chi-Ha Kai on Corregidor engaging American Positions.

The second leg of the Japanese advance, towards American positions on Malinta Hill, was spearheaded by tank commander Tsuchida and his Chi-Ha Kai. As the tanks drew near to the American defensive lines there, they encountered and destroyed prepared positions containing anti tank guns and the few Stuart tanks that had survived the battles on Luzon. This second engagement took place at Water-Tower Hill. The Japanese took no casualties during this engagement since Tsuchida's Kai destroyed or forced the surrender of all resistance met en-route to the American facilities.

 Having defeated all American resistance at Water-Tower Hill, the Japanese force took position some distance away from Malinta Hill and dug in awaiting further orders. Intimidated by the presence of the new Japanese medium tanks, on which the US forces on Corregidor had no information, one staff officer of the United States approached Tsuchida's tank with a white flag, asking for a compromise. Tsuchida ordered one of the infantrymen to direct the officer to the Japanese regimental HQ, where after half an hour talks ceased without a viable compromise. The HQ thus ordered for the advance on Malinta Hill to continue. Japanese forces began to open fire as the tanks continued down the road towards Mantila Hill. As they advanced,the Chi-Ha Kai tanks began targeting American pockets of troops scattered around the island's tunnels, with the fiercest fighting taking place near San Joseph tunnel.

Japanese forces move into the American HQ in the afternoon of May 6th.
Takahisa's Chi-Ha Kai can be seen at the rear.

 Eventually the tanks reached Corregidor's highest point, Malinta Hill. Once stationed there, the two tanks had a commanding view of the remaining American facilities and barracks. To their surprise, a white flag was raised upon their arrival at 2:00 PM, officially surrendering to the Japanese forces on Corregidor. On May 7, General Wainwright officially surrendered to the Japanese landing force, and relayed orders to remaining American forces on Corregidor to lay down their arms. It was at this point that the two Kai tanks under command of Tsuchida and Takahisa were brought to the attention of the Japanese public, and labeled as the "Tigers of Corregidor" in the papers. The American intelligence committee also referred to the new and mysterious medium tank as the “Tiger of Corregidor” until it was to later be known as the Improved Chi-Ha medium tank. While commanders Tsuchida and Takahisa were received as heroes back home, they never single handedly faced endless numbers of American tanks as the myth tends to claim. However, they did force the Americans to surrender the island, a task of equal merit. Their actions were documented in Japanese and American news reports, and the exaggerations therein became the basis for the myth.