Monday, September 3, 2018

O-I Superheavy Tank: A Complete History


The Battle of Khalkhin Gol had been a devastating defeat for the Empire of Japan in 1939. The Kwantung Army suffered total strategic defeat at the hands of the Soviet Union surrounding the village of Nomonhon. This had been Japan’s first significant deployment of armour against a modern army. Tank development in Imperial Japan was still in its nascent stages by the time the border conflict at Nomonhon began.

Notebooks belonging to the engineers working on the O-I/Mi-To tank project, and where majority of the source material from this write-up derived from, including all drawings.


Japan constructed a series of fortifications in Manchuria and central China under the supervision of the Continental Fortification Research Committee, a department under the Imperial Army. This committee oversaw all major defenses in the region against the Soviet Union and Chinese warlords. Shortly after the Nomonhon Incident, the committee submitted an idea to construct special purpose tanks that were capable of breaking through heavily defended Soviet lines and force the Soviet armies back out of taken Manchurian lands. Colonel Hideo Iwakuro, an officer in the Military Affairs Bureau Tank Research Team, took an interest in the Continental Fortification Research Committee’s proposal. Iwakuro sought to build super heavy tanks to fit the Committee's plan: tanks capable of withstanding fire from Soviet artillery and anti-tank guns while supporting infantry and medium and light tanks pushed through Soviet defensive lines.

Type 95 Ro-Go. Japans second heavy tank.

Japan built and tested an array of multi turreted heavy tanks from 1925 to 1938 in an attempt to implement a breakthrough vehicle. However, these tanks all had the same underlying issues; their armour was too thin to protect against anti-tank gun and their armaments were inadequate. Due to weak engines, these prototypes lacked sufficient speed and mobility, but forced the chassis to be larger. 




Colonel Iwakuro set forth to construct a tank to fit the Continental Fortification Research Committee’s vague proposal. In the early months of 1940, Colonel Iwakuro along with a team of twenty engineers from the 4th Technical Research Group to design the superheavy tank at their headquarters in the Tokyo area. The team held meetings in a secluded barracks, complete with multiple small fitting rooms, where they conducted meetings and wrote reports on the progress of the construction of the super-heavy vehicle. At the end of the barracks facility was a fully-enclosed room with no windows and soundproofed walls to prevent external personnel from overhearing discussions related to the project.

The superheavy tank project proceeded under the temporary name Mi-To. This came from the fact that Colonel Iwakuro had hired the Mitsubishi Heavy Industries Tokyo Equipment Manufacturing group producing the parts needed for the tank. Construction work would be performed by the Sagami Army Arsenal in secret. Colonel Iwakuro had taken on this project because he was capable of securing confidential funds from the Military Affairs Bureau, as he had been the section director at the time. This permitted Iwakuro to work on the project without the Army’s head officials knowledge.

Initial draft of the Mi-To's interior and suspension.

The Mi-To maintained the core design Japan had used with earlier heavy tank prototypes; a multi turreted chassis. The design version of the Mi-To weighed in excess of 150 tonnes, heavier than any tank of the era. The weight of this project came from the requirement of being impervious to Soviet anti-tank guns and artillery. The engineers working on the project expressed their skepticism on how feasible the tank would have been. However, the team, originally at 20 people, eventually dwindled to just 2 members. Funding of the project became unstable early in development as Colonel Iwakuro was been sent to a seperate division.

As was custom with Japanese heavy tanks, the Mi-To had a multi turreted system with two auxiliary turrets in the front part of the chassis, one primary turret in the center hull of the tank, and a machine gun turret located at the rear of the chassis. The blueprints for the Mi-To show a Type96 150mm Howitzer, and two new Type1 47mm guns in the front auxiliary turrets. Due to the excessive weight of the turrets, manual rotation would not be possible. Therefore, all four turrets were to be equipped with electric traverse drives.




Due to the heavy weight of the armour, the Mi-To required a special assembly to hold all the main armor plates together as the vehicle would have to be disassembled and reassembled  to send it across Manchuria to deployment zones. This frame was held together by 35mm thick mild steel plating pieces. This gave the vehicle a sturdy structure while minimizing the added weight to the vehicle. According to project engineer Shigeo Otaka, the tank was designed with frontal and rear armour 150 millimeters thick. Held together by the 35mm framing network. The side hull was 35mm thick with a 35mm side skirt for roughly 70mm of total side protection. The design of both frontal and rear protection is peculiar, but due to the design requirement being a mobile fortress, it seemed fitting. 

A primary feature of the super heavy tank was the ability to quickly disassemble the tank to transport it. Because of this, the armour plating were able to detach via the bolt-on frame.  The bottom of the vehicle had two plates welded together to support the weight of the chassis on top.



Construction officially began on April 14th, 1941. The Army Technology Division had taken control on the project after Colonel Iwakuro left. The project was now overseen by Colonel Murata, an officer in the Army Technology Division. Murata had not expected the tank to have been so underfunded when he was assigned the position. He planned to finish body construction within the first three months of the start of the project. Unfortunately, resources had already started to dwindle by the time the frame was halfway through construction. Mitsubishi Heavy Industries had been contracted to build the armour plating for the vehicle. These resources were sent to garage the Mi-To began construction at. After a single month of building, the  Army Technology Division had completely run out of materials, and weren’t even close to finishing the body.

Ventilation.
The Mi-To required more plates and electronics for the hull, but funding had already started to run dry. Problems with the cooling system and circuits delayed assembly by 9 months. During this time, the Division waited for more steel to arrive from Mitsubishi. The Sagami Arsenal had been contracted to supply the project with track and suspension assemblies. However, Sagami had not followed through with initial requests. The arsenal had also been asked to supply the 150mm steel plating used to construct the turrets for the vehicle, but the steel could not be allocated. Japan lacked steel for production, much less prototyping. This caused the turrets to be delayed for over a year. Within the first year of the projects start, the Technical Headquarters had considered to canceling the entire project multiple times. 

Mitsubishi managed to finish the Mi-To’s hull in February 1942, a month after construction restarted. The suspension and track links were built by this point and installed.  While the engine compartment had been worked on during late February, (1942), both side plates had distorted and collapsed due to the heavy rear armor and thin supporting side armor. This forced the engineers to place another 10mm steel wall in the engine compartment to support the weight of the tank. The 150mm plating for the front and rear of the Mi-To could not be built due to the lack of steel. The front and rear of the tank were to continue with single 75mm plates. An idea to produce an additional 75mm plate out of structural steel to make the prototype look as it would in production was proposed, but did not occur.


Prototype suspension.


On March 16th, a meeting was held by the Sagami Arsenal, Technical Headquarters, and engineers from Mitsubishi to discuss the design of the tank and the limited communication between all eleven members of the tank crew. Coordination in combat was a necessity. As such, a telecom system was to be installed in the prototype. Members of the cockpit, auxillary turrets, primary turret, and engine room could all phone-into each other to address orders and concerns that may arise during operation. The interior of the tank was to be. Crew could walk to and from each section of the vehicle by walking through two doors on the left and right sides of the tank. These sections were divided by two steel plates protecting the engine department, combat quarters, and drivers compartment.

On March 20th, the turrets began construction again but at a slow pace due to a lack of thick steel. In the meantime, a wooden mockup turret was built and was to be placed on the prototype with weights added to simulate the completed vehicle. The auxiliary turrets managed to finish in relative timing by June 4th.


Driver's periscope. 


The cockpit of the Mi-To was placed in the center of the chassis, sandwiched between the two 47mm auxiliary turrets. The driver’s vision was provided by a three sided periscope, each side measuring 178mm across. Operating the tank was difficult for the driver, as the clutch, brake, and transmission levers were far from their respective components at the rear of the tank. The Mi-To had a length of over ten meters, causing the tank to have low responsiveness to driver input. Therefore, a pressurized oil tube acting as a transmission assist had been installed in the center of the chassis, and the steering mechanism was given a hydraulic assist. The transmission, similar to that installed on the Type 97 chi-ha, had four forward gears and a single reverse gear. The transmission controls were placed in front of the driver and the steering handles at his sides. 

Driver's lever mapping.


Prototype engine RPM range.
The Mi-To was to be powered by two engines instead of one due to the excessive weight of the tank. Two Kawasaki V-12 800 horsepower engines were installed on the left and right sides of the engine room. The engine mounting layout of the vehicle resembled the design of the Type 89 I-Go. The driveshaft of the engines turn the cooling fan before going into the transmission. The transmission is connected to the multiple disc clutch between the two engines. The power is then transmitted to the final drive gear through the steering linkage extending to the left and right of the rearmost mechanism, and moves the drive wheel at the rear end of the tank. The two engines were originally supposed to be supercharged. However, the superchargers had too much parasitic power loss and produced excessive heat at high RPMs. The superchargers were removed, leaving the power output at 700HP per engine. This was further lowered as the cooling systems required 100HP out of each engine in order to keep the metal from melting. Final output at the wheels were 600HP per engine, 1200HP total.

The Mi-To could carry 400 liters of fuel. The fuel tanks were stationed at the top side of the hull at the rear. These were vulnerable to fire from the side of the tank, and during redesign the fuel tanks were to be relocated under the main turret and given a welded steel cover for protection. However this did not make it onto the prototype vehicle. 

Fuel line linkage to engine.


The construction of the suspension, hull and secondary turrets of the Mi-To finished in early 1943. The chassis weighed 47 tons empty without additional armour. The tank weighed 97 tons when configured for mobility and defensive tests, but this did not include the weight of the turrets. The Mi-To weighed 120 tonnes when the three auxiliary turrets and other pieces of armour were installed. The primary turret and additional 75mm plating would have given the tank a weight of 150 tonnes, just as designed. The vehicle had an overall height of 3.360 meters, width of 4.840 meters, and a length of 10.120 meters. Both tracks were 760mm wide. 




Tank Weight and additional armour plating weights ^

One project engineer the 47 ton chassis for mobility tests outside of the garage at the Mitsubishi facility. When driving with the first two gears, the Mi-To operated without any issues. Driving took place at the night, around tight street corners. This meant shifting into second gear was difficult, but there were no mechanical faults in the brief test. The speed topped out at 40kph on a straightaway. Major General Tomio Hara visited the site of the Mi-To’s construction before it was to begin official prototype trials and he had been pleased with the hydraulic suspension capability of the superheavy tank.




The Technical Headquarters decided disassemble the tank on May 26th to relocate it to the Sagami Arsenal, 51km from Tokyo. This process had all light plating removed from the tank alongside other equipment non-essential to the vehicle’s structure. These removable parts included;
Track Link

Upper deck plate, floor board plate, operating cabin desk, turret panels, turret room upper deck, tank hull rear upper plate, tank side plates, engine upper deck plate, engine room upper rear plate, upper track roller, lower roller wheel, suspension spring, spring covering, engine motors, engine starter, air filter, cooler, oil cooler, oil tank, fuel tanks, exhaust piping, muffler equipment, storage batteries, etc. 




Weights of varying parts on the tank ^

Removed parts were transported by truck to the Sagami Arsenal. All parts were covered by a wooden box at the rear of the trucks to hide components as to prevent citizens or potential spies from discovering the super heavy project. The main hull was placed on a 30 ton trailer, and towed by a 13 ton tracked towing tractor. The turrets were towed by Type 95 Ha-Go light tanks and a Type 97 Chi-Ha. Moving all the parts took 19 hours from Mitsubishi’s construction center to the arsenal. The tank did not get completely disassembled until June 9th. Once at Sagami, assembly began again on July 1st. Once completed on the 20th, the trials were scheduled to begin on the 1st of August.


Prototype chassis being towed.


On the day of the trial, high ranking officials in the Army were present to witness the first Japanese superheavy tank in motion. The Mi-To received a name change to O-I to follow Japanese naming convention (O translating to Heavy, I for First, making it "First Heavy") that was standard. Colonel Murata had been sent away for other purposes, and in his place was Lieutenant Colonel Nakano, Murata's assistant and colleague. Tomio Hara, head of the Sagamia Army Arsenal, was also present for the trials. 

Conditions for the trial were poor. Weather during the previous days caused the soil to soften, and terrain to become uneasy. The road at the proving grounds was narrow and when the O-I began moving down the road, the tank started to drift off the road and damaged the roadwork, resulting in the tank sliding off the road and into the soil. A change in the trial planning focused on the O-I traversing around in the dirt next to the facility it was kept in. Due to the surrounding buildings, its top speed could not be showcased, and traversing was difficult. The weight of the vehicle caused the land to start sinking in during pivots.  The tank managed to reach speeds of 18.7km/h at normal intervals. At full throttle, the tank could technically reach 29.4km/h.


driver's recollection of events.


The O-I reached the first three gears in its mobility test. At the end of the first day of the trials, the O-I had been put back into its garage and the engineers noticed that the seventh lower track roller’s bearing had been damaged, pinched between the drive sprocket and the outer plate rolling wheels come off on the right side of the tank were damaged, the roadwheels came loose, and it was caught between the drive sprocket and the outer plate skirt. The outer plate had broken through, and the gear of the drive sprocket broke apart into two pieces. 


Driver recollection of the chassis sinking into the mud.


The O-I had two bogies on each side, each bogie containing four wide roadwheels. The wheels were of cast construction and lacked rubber lining. During movement, the O-I chassis experienced severe rocking motions. Heavy duty shock absorber assemblies were placed inside the vehicle. The shock absorber was to connect the top and bottom of the vertical spring with two rods extending from the two front and rear swaying. One shock absorber supported the weight one bogie. The total ground pressure was 1.5 kg/cm^2 in soft terrain.

driver's recollection of events and damages sustained. 


American recalling of various Japanese
Prototype tanks.
From August 3 to August 8, the engineers began repairing the damage that had been done to the tank. 32 of the total 64 bearings were broken during the tests due to the bearings having insufficient strength. The excessive weight of the O-I caused the entire right side of the tank to collapse when at an extreme angle. Engineer Shigeo Otaka recalls the O-I undergoing immediate repairs to continue its trials. However, due to the steep cost of the repairs, they were put on hold for over a year, with the tank staying at Sagami Arsenal until March of 1945. The war had been nearing its end, and the usefulness of the O-I in Manchuria began to fade. The Soviet Union was no longer Japan’s primary enemy, and the development of more powerful anti-tank guns by the Soviet Union made the armour protection of the superheavy tank obsolete. The project to built a single prototype unit came at a steeper expense than originally thought possible, mass production was not realistically possible for Japan during the war. The project had thus been deemed a failure.

When the United States occupied Japan in late 1945 and began conducting Intelligence work at Japanese arsenals, an inquiry was made with the Sagami Arsenal specifically. The US force demanded details on the various prototype tanks located there to be sent with detailed specifications to the US forces in Japan and have the prototypes taken to the Aberdeen Proving Grounds in the US. Whether the Japanese scrapped the vehicle before the US arrived or if the United States managed to secure the hull and had it scrapped with other prototypes such as the Chi-Ri and Chi-To at Aberdeen remains unknown. All that is left is a single track link from the prototype. 


I have uploaded many of the original drawing schematics of the O-I to a single PDF file. As there were too many images to include in the article itself.



Saturday, August 25, 2018

Tank Battle of Khalkhin Gol

It was the eve of June 20th, and the Japanese headquarters in Manchukuo enacted emergency mobilization of the 3rd and 4th Tank Regiments. Soviet armies moved alongside the Manchurian border, preparing to retaliate for the border skirmish between Mongolian calvary units under supervision of the Soviet Union, and Manchurian infantry regiments. A border dispute between two puppet states forced the response of the Empire of Japan and Soviet Union to mobilize their borders.

The emergency dispatch called for the tank regiments to move towards the village of Nomonhan, northern Manchukuo. Colonels Yoshio Tamada and Kiyotake Yoshimaru led the tank regiments alongside the Kwantung Army to the frontline.  On the 21st, railway transports began loading and transitioning the Japanese tanks of both regiments, and arrived at the checkpoint in northern Manchuria. Colonel Tamada ordered maintenance work to begin on the 23rd of June, finishing preparations to advance through rough terrain. The long roads had become muddied by rainfall, and scorching temperatures began to overheat tanks as they moved towards the line. The tank regiments were delayed 2 days attempting to make their way through the unfavourable land.

Japanese Tank Regiment's pushing around the Harzha River to the frontline.


The Kwantung Army decided to cross the Harzha River and to proceed across the left bank of the river. The army failed to accurately gauge the depth of the river, as the tanks of the 4th and 3rd Regiments were incapable of fording it. Lack of communications forced Colonel Tamada to force his way across and catch up with the main army. On June 29th, Japanese aerial reconnaissance reported spotting the Soviet army retreating backwards away from the frontline.

Soviet 45mm 53-K captured by Colonel Tamada's
 4th Tank Regiment on June 30th.
The 3rd and 4th Tank Regiments  were held in the farm of Handagai, awaiting further orders. Due to the lengthy moving north, fuel supply dwindled to critical levels. This forced Colonel Tamada and Yoshimaru to cut their forces down and take forward a limited number of tanks and cars. On June 30th, the group began moving once more to catch up with the moving Soviet army. Report came in for Colonel Tamada, stating the vanguard 9th Squadron had made contact with Soviet forces at 9:00AM. The 9th was led by Captain Kitamura, a close friend to Colonel Tamada. In attempting to engage Soviet forces, a 45mm gun knocked out a Type 95 tank in the leading patrol. The surviving crew recalled that the blast had been made before they even noticed the flash of the gun.


 Tamada pushed his force forward, managing to catch up with the 9th Squadron by 12:30PM. Tamada moved his tanks into attacking positions, while ordering the 9th Squadron to push forward and attempt to scatter the Soviet forces. Eight BT tanks supported by three armoured cars and a single 45mm gun placement comprised the attacking force. The Soviet forces managed to retreat out of sight of the tank regiment during the fight. It was noted after the battle had ended by 2:30 PM that it had just been a scouting force under command of the Soviet 11th Tank Brigade. The 45mm anti tank gun in this engagement had been disabled by Tamada. This was the first tank engagement Japan experienced against a modern military. Tamada noted that after the battle had finished, it became apparent the war would not be easy. The Soviets were better equipped compared to the lacking Japanese equipment. After the engagement, Tamada’s regiment was ordered to stop and refuel all tanks and to wait until the second push was to be called upon.

Type 95 Ha-Go under command of Tamada's 4th Regiment.

The 3rd Tank Regiment under command of Colonel Yoshimaru was accompanied by an allied infantry group, the 64th Infantry Regiment, and planned to assault entrenched Soviet artillery positions in the Manchurian prairie. The 3rd regiment secured itself next to a local lake, and prepared to launch its forces. Aerial scouts reported an opening in Soviet positions to their right. The 3rd Regiment decided to attack there, however the weather took a turn for the worst, and heavy rains prevented the company from pushing forward with the attack together. The battle was delayed until the next day. At 8:00AM the following day, Colonel Yoshimaru was to send his force to the right flank of the Soviet position, while Colonel Tamada attacked the left. Japanese artillery managed to move into a position to support the three regiments in their attack.


Colonel Yoshimaru lost his confidence when piano wire disabled two of his Type 97 Chi-Ha tanks in the open field. One was disabled by anti tank fire from a Soviet 45mm. Captain Koga of one of the tanks that had been disabled by the barbed wire had armed himself with the turret rear-facing machine gun mount and fired upon Soviet infantry to his sides. Once emptied, Koga opened his hatch and fired with his handgun at the Soviet troops. Captain Koga was killed shortly thereafter, but not until he had spent an hour and a half fighting desperately to cover his units vehicles.

The Colonel was operating another Type 97, and with his forces aiding in the battle, disabled a handful of armoured cars and tanks. Soviet troops began to rush the 3rd Regiment’s tanks with anti tank grenades, but were quickly gunned down before they could be a threat. However, while the 3rd and 4th Regiment managed to force a Soviet withdrawal, the Japanese 64th infantry were unable to push forward in time, and both tank regiments were forced to retreat without allowing the infantry to keep the newly obtained position. The battle had ended by 10:30 PM. This engagement costed the 3rd Tank Regiment two of its newly fielded Type 97 tanks, leaving only two left in their possession. The 3rd and 4th Regiment combined had 93 tanks at their disposal. The mainstay being comprised of Type 89 and Type 95 tanks.

With no sign of infantry support, Colonels Tamada and Yoshimaru contemplates their next move. Yoshimaru had suggested a forward assault into the Soviet position while having Tamada support the right wing. However Soviet forces had heavy howitzers in their possession preventing any frontal assault. Without infantry, the tank regiments were unable to find a favourable method of attacking. Colonel Tamada suggested a night attack using the uneven terrain as a vantage against the soviet forces. Most however were against the plan. Tamada had to inform the troops that unless a night approach was taken, the company would perish taking the Soviet position.

Famous painting illustrating the night assault on Soviet Lines. The painting had been present in Tamada's recollection of the battle.

At 11:30PM on July 2nd, both regiments pushed forward under the cover of darkness. Tanks were ordered to move at their slowest possible speed in order to prevent loud noises from alerting the Soviet forces. Tanks were not to fire until enemy tanks and artillery were spotted at a range of ten meters. Seemingly out of nowhere, weather decided to favour Colonel Yoshimaru and Tamada. A thunderstorm erupted, covering any noise that could be heard from the Japanese tanks. Moments after, the crackle of lightning lit the field for both sides. Soviet troops had been met upon tens of Japanese armoured tanks only meters away from their encampment. Japanese tanks opened fire, pounding Soviet armour and artillery without pause. Tank commanders were instructed to destroy rear artillery as their priority. Although once the fighting had erupted, organization became impossible. Each tank and its crew operated by itself.


Damage done to one of the Ha-Go tank under Tamada.
Colonel Tamada knew the Soviet line would not allow a breach, and a Soviet counterattack was only a kilometer away from engaging. Tamada ordered a full retreat once the attack had accomplished its goal. Fuel supply had also run short, preventing the company from staying any longer. The tank regiment managed to destroy 20 Soviet tanks, 10 armoured cars, and 20 trucks and their artillery. Only losing a single Type 95 tank in the process.

Following the massive attack the night of July 2nd, Colonel Yoshimaru had been instructed to attack the Soviet line once more. As no infantry support was present, defensive preparations of the Japanese position were not made. Yoshimaru understood that the line may have been weakened by their night raid, however by the next day Soviet reinforcements strengthened their position. Nonetheless, an assault was made by the Colonel. The 3rd Regiment had been immediately met with anti tank fire by field guns and BT tanks. Colonel Yoshimaru had been killed in the assault, along with 12 other tanks. The Soviets lost 3 BT-5 tanks and 8 anti tank guns as a result of the attack. The Soviet commander reported to his superiors the grand defense of the line resulted in many destroyed tanks. The battle was later known as the Nightmare of the Piano Wire, as the Japanese tanks had been trapped on the Soviet-placed wiring in the field, allowing Soviet guns to easily target their tanks. It was not until much later that the Japanese managed to recover their tanks and repair them.

The photograph above was taken during an experiment
after the battle showing the damaging results of piano
wire entanglement.

The tank regiments kept position until infantry support arrived, and the Soviets managed to once more reinforce their losses. At 7:00AM on July 4th, the Soviets decided to finally attack. Their force was  comprised of 19 tanks (both BT and T-26 models), 20 armoured cars, and 500 infantry. The tank regiments had infantry support during this battle, after days of fighting alone. It came as a relief to the tank crews. Japanese tanks were positioned on ridge lines as to cover their hulls from anti tank fire. The Soviet 45mm was superior to the Japanese tank guns used during the incident. Japanese crews knew this and adjusted tactics accordingly. The battle lasted until 4:00PM, once the Soviet Union’s armoured force had been crushed a retreat was ordered.  The Soviet Union lost tens of armoured vehicles during the entire engagement on the front line. The Japanese only lost a single Type 89 tank in their first attack.

The Japanese line had shifted backwards. A retreat was ordered to reinforce a new line. The Soviet Union strengthened their attacks for the next 5 days. More forces were sent to attack the line - and no reinforcements by the Japanese to accommodate losses. The Japanese tanks sat on defensive ridges and fired at what they could of the attacking Soviet armoured force. With limited infantry support, the defense quickly crumbled in the face of the attacking Soviet army on the fifth day of the assault. Tamada’s regiment began with thirty-six Type 95 light tanks, eight Type 89 medium tanks, and four Type 94 tankettes.


Disabled Soviet BA-10 Armoured Car.


By the end of the assault, only four Type 89 medium tanks, four Type 95’s, and the four Type 94 tankettes remained. Japanese artillery covered Colonel Tamada’s fall back, barely saving what little he had left.  The 4th Tank Regiment and the remains of the 3rd had to leave the line for repairs and reinforcing.  The Kwantung army criticized this choice by Tamada, as they claimed success would not go through without armoured support. However due to days of tank fighting without the aid of infantry, the tank regiments’ morale was shattered.

Tamada's Regiment performing maintenance work.
Japanese military commanders heavily criticized the decisions by the Japanese tank commanders. Due to their ultimate withdrawal, the infantry officers stated that Japanese tanks were useless, and were all destroyed from simple piano wire. Certain officers made claims that despite losing a battle, they remained to see it through, while the tank force retreated when it became hopeless. This view on Japanese armour stuck for the remainder of the war. Japanese mechanized tank units were banned, and were chosen to instead accompany infantry attacks in their doctrine. The 3rd and 4th Tank Regiments had shown great success in proving the capabilities of Japanese armour despite the overwhelming disadvantage in numbers and quality of Soviet tanks. Having success in their engagements, the armour unit proved their worth. However, Japan’s ultimate strategic failure and incapability of establishing proper communication between tanks and infantry overshadowed that success. Japan suffered a heavy defeat to the Soviet Union at Nomonhan. These lessons were only properly addressed after the incident.


Saturday, January 6, 2018

Postponement of Work



  Hello everyone. It's been quite some time since I last updated my blog. Unfortunately, I've had troubles working due to various reasons, so my time to update and work on my research and articles has suffered because of it. So today I am going to post my final Blog Update for the near future.

As of January 6th, I'm due any day now for my baby boy. 40-weeks finished, and my little one is near ready to come into the world. However, for reasons I do not wish to go into detail on, I have been listed as a High-Risk Pregnancy. I have a life-long history of poor cardiac health, and this pregnancy has made my complications worse. I am told that everything has a good chance of being a-ok, so I am not worried. But nonetheless, my health decline puts a severe damper on my ability to work and share with the community. The Doctor told me I am forbidden from partaking in flights for 6 months because of my health with high altitudes, so that unfortunately means I will not be able to visit Japan again until late next year at best. Projects I had planned to perform are not really possible now, so until I have the opportunity to get back into the depth of things, I'm sad to say I wont be able to release as many things as I planned to.

I would like to apologize for those eager to get their hands on new content from me. I know that there has been much Ive been working on, many articles that are currently in the works I cant quite post now because of complications.

As for those in the War Thunder Community; my work with Gaijin will also be taking a pause. Due to health concerns and the fact I now have a baby boy to look after, my work with Gaijin Entertainment will be considerably slower paced. However I would like to keep this pause short as there are things to take care of. But of course, stepbacks.


As a farewell present, here's a little something for you all. I did not plan on showing any of what I found and received for the Ho-Ri last year. I planned on using all my material for my book. However I wanted to give something away as a little compensation. So heres one of the Ho-Ri technical drawings;





For those not apart of the /WarThunder Reddit, I have posted semi-regularly in regards to brief posts on Japanese Vehicles. If you are looking for information on a vehicle not covered on the Blog, try looking on my Reddit here; https://www.reddit.com/user/MaiWaffentrager/





- Seon Eun Ae & Baby Ri 😊







Friday, October 6, 2017

Ohka-based Interceptor Fighter

Recently I spent some time in the National Archive of Japan and the National Diet Library Center. I eventually found, with help of a friend procuring documents from the Canadian Heritage archive, a new type of Japanese interceptor based on the Ohka Suicide Bomb. I don't usually touch on aircraft, as my aerial knowledge is rather poor. To make this I worked with a few people who have a much better understanding than myself. Such as Cherryblossom, ARADO_AKBAR, Shapeshifter (Whelmy), and Leo Guo.

The aircraft, dubbed the Suzuka-24 by American Intelligence, was an interceptor rocket-based aircraft designed to intercept allied bombing formations at the end of the war. Unlike the Ohka, this new rocket was not intended to be used for kamikaze use, instead for a complete take-off, strafing run, and landing.

The following file material was used to construct the Suzuka 24;


  • US Intel Report No. 63a-6 Rocket Powered Aircraft
  • US Intel Report Report No. 9-a-60 Rocket Plane "Ball of Fire"
  • R.A Liaison Letter, July 1945 



Ohka Development Background 

As the end of the war drew quickly for Japan, the military started relying on drastic measures to achieve the most in the short window period they had left in the war. Such measures involved the use of suicide operated vehicles and weaponry - with the intend on using a platform loaded with explosives to crash and detonate the targeted object. From tanks, ships, infantry weapons, and most noticeably aircraft. The term Kamikaze was used heavily in reference to the suicide attacks via pilots, flying fighters and heavy assault vehicles where were equipped with explosives used to ram United States ships.


Photograph of the Ohka rocket, with its
warhead next to the nose.
With the United States Navy closing in on the Japanese home islands, and the lack of Japanese fleet warships left, the Navy Air Service were met with troubles on how to deal with the ships, especially American aircraft carriers. IJN ensign officer Mitsuo Ohta devised an idea of the use for a rocket powered aircraft designed to carry a large warhead that could be used to ram into warships at excessive speeds. Ohta was a member of the 405th Kōkūtai, a transport flight pilot with limited aero engineering experience. His concept was forwarded to the Aeronautical Research Institute, held at the University of Tokyo, where students became fond of the idea, to which was
 then sent to the Yokosuka Research Facility. The concept of the suicide rocket were eventually adopted as the project MXY7, and technical drawings and blueprints were drawn for the rocket.


Flight path of the Ohka leaving the G4M.
Designed to carry three Type4 Model I rockets, the MXY7 would have its first powered flight in November of 1944. The idea was simple, and deemed effective for use. Mass production of the aircraft began as soon as it came in. The designation Ohka was given to the suicide rocket, and 755 units of the Ohka were built at the Yokosuka and Kasumigaura naval arsenals. The rocket saw limited use, with only a handful of successes resulting in American warships being sunk.

The Ohka was transported by a mothership, the Mitsubishi G4M Betty. While considered for land and submarine deployment, it was never conducted with the suicide-purposed models.




 


Suzuka 24

The Ohka rocket from 1944 to 1945 went through several design changes. With the underlying change of which for different warhead sizes and powertrains. All of the models shared the same underlying theme -  suicide use against warships. However by 1945, a new threat emerged to Japan, American strategic bombing raids. The introduction and use of the Boeing B-29 Superfortress posed a substantial threat to Japanese aircraft. To remedy this issue, development of new more powerful fighters took place. Not only, but correspondence with Germany resulted in sharing of rocket and jet engine information to Japan. Such examples and information would lead to aircraft such as the Kikka and Ki-200 to be built at the end of the war.

Suzuka 24 POW sketch.

Rocket development became heavy in Japan, with multiple designs being built. It was decided to redesign the Ohka for a new role - bomber interception. Similar in operation to the Ki-200 rocket, the Ohka-based interceptor would be lighter in weight, smaller armament, and a small silhouette. The Ohka was designed by the Japanese Naval Air Service, however the change to use a land-based interceptor was developed by either the Navy or Army air serviced, currently unknown.

The new design removed the use of a warhead entirely. As its purpose was intercepting B-29's, the weight and use of a warhead was seen as impractical and hazardous to the design. Instead, a fuel tank and two 20mm cannons were placed in the nose of the design. Due to this, there is no room in the nose to fit a warhead of any size. With only a length of 6 meters, the 20mm cannons take up a considerable worth of space to fit the gun and munition belts properly. The design of the aircraft was significantly altered to account for its new use. A changed tail design, now introducing a general vertical and horizontal rudder and elevator, allowing better control of the aircraft in flight. Along with this a longer wingspan, being 0.5 meters longer on each side of the aircraft and thicker support. The new design of the Ohka-interceptor allowed for ease of maneuverability in flight. 



The Ohka interceptor was produced in a handful of models. By the time the war ended in 1945, most of the vehicles were kept at Suzuka, Yokosuka, and Kanoya airfields. United States Intelligence discovered one model at Suzuka, and labeled the aircraft as the Suzuka-24 as the official designation was not known.

Four more models of the Suzuka-24 were discovered at Kanoya airfield. At Yokosuka, another model was found along with a pilot belonging to the airfield captured. The pilot listed details of the aircraft, its designated use being bomber intercepting, and measurements of the aircraft. Photographs were mentioned as being taken, however at this time none have been found.




Combat History

The Suzuka-24 saw only two accounts of combat. Both were separate engagements on B-29 formations on April 3rd, 1945. The bomber crew report the Suzuka-24 being a "ball of fire" in accordance to the rocket's discharge. The report lists the rocket lasting for 6 to 8 minutes, where the rocket finally died and the aircraft broke off from the B-29 formation. The crew report matched the fuel time the Suzuka-24 could sustain, 7 minutes. To reach the formation, the Suzuka-24 was given an assisted-rocket on the underside of the central fuselage. 

They note the rockets flickering on and off while chasing the bombers. Due to the KR-10's being new and flawed, performance reflected operational use. The Suzuka-24 struggled to get even with the B-29 bombers during its engagement. Overpassing and following behind due to the flickers. The KR-10 by April 3rd were highly experimental. Even when mounted on the J8M prototype months later, the KR-10's operated poorly and even resulted in exploding due to the rocket mixtures.


Known Statistics and Performances

Only a general look of the Suzuka-24's specifications are known. 
B-29 report on seeing the Suzuka-24 in action.


General characteristics
Crew: 1
Length: 20 feet aprox. (6.097 meters)
Wingspan: 20 feet aprox. (6.097 meters)
Height: N/A
Powerplant: KR-10 (presumed)

Performance
Maximum speed:  N/A
Maximum Glide Speed: 840 kmh (520 mph)
Rate of Climb: 10,000 feet per minute (3,050 meters per minute)
Range: 7 minutes of fuel
Service ceiling: 32,000 feet (9,755 meters)

Armament
Guns: x2 20mm Cannons (60 or 150 shells per gun) (Unknown Ho-5 or Type99)
Bombs: None

Misconceptions 

After the war, the United States encountered many different aircraft. Multiple variations of the Ohka were made and left over in mixed conditions. Because of this, the Suzuka-24 is confused to be an identical Ohka with a warhead, the Model 43B.  The Model 43B was similarly designed to hold two 20mm cannons. However the fuselage was extended to carry both the cannons and warhead with fuel for a Ne20 jet engine.


I'm working on collecting the technical drawings and other details at the moment. When I have them, I will make sure to update the post. [10/5/17]

Friday, June 23, 2017

Through the Gauntlet

It is not often you hear of Japanese war heroes during the War in the Pacific. Due to their reputation, many cases of Japanese bravery went unnoticed as the years went on. Often set aside to instead forget about the tragedies and brutal events that took play throughout the Second World War. However if any account of bravery is to be known, it is the actions of a single tank commander of the Imperial Japanese Army during the Battle for Iwo Jima. A man who took personal responsibility and dared to do the unthinkable to protect his comrades when all had seemed lost. The Battle for Iwo Jima had been one of the most brutal and bloody battles of the war. Japan's last hope of defense against the invading American forces, who needed the island in order for its long range bombers to reach the home island of Japan.




26th Tank Regiment

Takeichi Nishi during the 1932
 Los Angeles Olympic Games.
One of the commanding officers on Iwo Jima was Baron Takeichi Nishi, in charge of the 26th Tank Regiment and its 600 personnel. Takeichi Nishi had been Japan's 1932 Olympic Gold Medalist in equestrian show jumping during events at Los Angeles. and regarded as a celebrity in both Japan and the United States. He had been assigned as the commander of the 26th Tank Regiment in Northern Manchuria for the preparation for a possible Soviet invasion. Nishi and the 26th were stationed in Mudanjiang, which held one of the key logistical railways for supplying the Imperial Japanese Army; should the IJA lose control of the railway, the Soviets would be able to make significant territorial gains. In spite of this risk, the tides of war began to shift; Nishi and the 26th Tank Regiment were eventually ordered to Iwo Jima, to bolster the garrison of Lt. General Kuribayashi on the island fortress. Prior to this deployment, Nishi had been promoted to the rank of Lieutenant Colonel in recognition of the distinguished conduct of the 26th Tank Regiment in Manchuria. Yet this award was effectively hollow; the 26th Tank had no actual combat experience. The same was true of many of the units already on Iwo Jima, which Nishi and his regiment were being sent to reinforce.



Defending Iwo Jima

Preparations for the defense of Iwo-Jima were made under the command of Lieutenant General Tadamichi Kuribayashi,  whose forces were told hold the island at any cost. Kuribayashi had been personally selected by Prime Minister Hideki Tōjō to be the head commander of Iwo Jima due to his reputation as the prior commander of the 2nd Imperial Guards Division. Kuribayashi knew the United States outmatched Japan in all fields; when the defense would begin, there would be no equal ground for engaging the Americans in the field. To counter the Americans, the Japanese defenders would attempt to use attrition to defeat the invasion force. In preparation for the execution of this strategy, the garrisons on Iwo Jima constructed 10 miles of underground tunnels throughout the island. These linked roughly 6000 fighting positions, including pillboxes and caves for gun-emplacements.

An example of a dug-in tank. 
The 26th Tank Regiment only had 23 tanks stationed on the island by the time the American forces arrived. Originally, there were 28 tanks (Mostly Chi-Ha Kais) assigned to the defense of  Iwo Jima, however on July 18th, 1944, a cargo vessel carrying the tanks had been sunk by an American submarine, the USS Cobia. Takeichi Nishi had been forced to wait for a new set of tanks to be supplied to the island. Only 23 units were able to be scrounged up for Nishi and the 26th to use in the defense of Iwo Jima. Among these 23 tanks, there were twelve Type 95 Ha-Go light tanks and eleven Type 97 Chi-Ha tanks. Of the Chi-Ha’s, only 3 were Kai models with the 47mm Anti-Tank gun. Takeichi Nishi decided to use the tanks as pillboxes on the rocky terrain of Iwo Jima. Their weak armour could not match the American M4 Shermans, however they were still a threat to infantry with their guns given appropriate protection by the geography.
The tanks were scattered across the island in various
positions to ambush the American forces as they moved inland.

By the end of 1944, the island’s garrisons reached 12,700 troops of various reserve divisions who mostly had been kept in China during the war, with little experience. 3,000 naval troops were also stationed on the island.  It came as a surprise to Lieutenant General Tadamichi Kuribayashi when the year had ended without any offensives by the Unites States. Japan had expected the island to come under attack sometime during 1944, but nonetheless no such attack happened. It wasn't until the middle of February that the American navy had came with a force of over 110,000 troops to take over the island from the already well-prepared Japanese. The naval bombardments began a few days before the landings were to commence. On the 19th of February, the landing forces stepped foot on the island, and the battle of Iwo Jima had begun.

Tank Trouble

4th tank Battalions combat report.
The American landing forces were met with stiff resistance the moment they came off the beachhead, however it only took 4 days for the American marines to capture Mount Suribachi and establish a major foothold on the island. Dug in within the various underground tunnels, the Japanese kept themselves hidden in order to take advantage of the American marines as they advanced further inland. The Americans had also deployed armoured units in the form of LVT's and M4A2, Shermans to support the advancing marines. However, due to the size and attraction the tanks caused on the island, the marines often pushed without the help of tank support. This led to infighting between company and tank commanders. Instead, most of the tanks moved to the northern airfields without heavily relying on infantry to safeguard the way for mines.

A Taken Out Chi-Ha Kai on Hill 382.
Sherman tank crews were forced to rely on their comrades and fellow tank crew’s for advancing inland. Due to the lack of available engineers on Iwo Jima, the crews had to manually leave their tanks to scout out the rocky terrain to judge how viable crossing would have been. This became apparent to the Japanese 26th Tank Regiment on February 20th, when a marine regiment alongside a tank company assaulted Hill 382 against the Japanese positions supported by tanks of the 26th. The engagement lasted until the 27th when the marines took the hill. Losses on the American side amounted to eight M4A2 Shermans, with another four damaged. The 26th Tank Regiment’s losses are unknown, but all the tanks supporting the defenses of Hill 382 were destroyed. The remaining Japanese tanks and crew retreated further North to Hill 362c. However, while the majority of the 26th retreated, a pocket of tank crewmen decided to stay behind and garrison a cave to ambush the oncoming American forces as they pushed past Hill 382.


On the 28th of February, American marines were unexpectedly attacked by Type 97 Chi-Ha tanks, in a desperate measure to prevent the advance. While surprising the infantry, the tanks were not an issue due to American bazooka’s quickly disabling the attack.


Hill 362c

After the battle of Hill 382, the remains of the 26th Tank Regiment positioned themselves on Hill 362c, one of the last remaining Japanese defenses on Iwo Jima. At this point, there were only 2 tanks left to defend the island. Lieutenant Colonel Takeichi Nishi had been reported as Killed In Action by the time the Japanese had finished gathering on Hill 362c. The American forces had kept the battle on hold temporarily as forces recuperated and were reinforced with supplies and replacements. The 21st Marines and 4th Tank Battalion were ordered to push for a final assault against the Japanese, and take Hill 362c from the defending forces. The United States had successfully captured most of the Island, and only a small pocket of Japanese troops were left. However, the last few Japanese knew that the island mustn't fall at any cost.

The assault on Hill 362c began on March 6th. The 21st Marines scheduled for a naval bombardment on the hill in an attempt to scare the Japanese out of their defenses. The first shells landed at 0845 hours and lasted for quite some time. Once the shelling had ceased, almost abruptly the Japanese began to return fire on American positions. As infantry attacks would not work, the 21st asked for the 4th tank battalion to attempt an assault on the hill. Three M4A2 Shermans were sent across the field to attack the Japanese positions mid-day.


Daring Hero

Photograph of Sec Lt. Otani Michio.
During the defensive, Japanese morale had been shaken despite their self perseverance. The remaining troops did not have the sufficient arms to defend against the oncoming Sherman tanks. However, the 26th Tank Regiment had one remaining Type 97 Chi-Ha Kai on the hill. Its crew being almost entirely killed with the exception of the commander, Second Lieutenant Otani Michio, who had been able to keep the tank covered during the bombardments. Otani Michio had been short on remaining munitions, and the tank being damaged beyond further repair at this point, was left to hold off an American tank column alone.

Otani Michio had the three tanks in his sights as they advanced. His Chi-Ha Kai covered by the terrain, his 47mm anti-tank gun had been able to successfully take out a Sherman within 100 meters of his position. Afterwards, Otani fired his remaining shots at the second Sherman tank, however unable to effectively penetrate and destroy due to the angle of fire the tank was positioned in. The crew had likely bailed due to damage of the repeated hits to the side. It is unknown what happened to his tank, however the gun was no longer useable after firing upon the second Sherman. Shocking his comrades, instead of retreating, Otani instead decided to exit the tank and sprint towards the second Sherman he had fired at. An unprecedented move, Otani managed to get on top of the damaged Sherman.

The damaged Sherman, crewless, gave Otani the opportunity to deal with the remaining M4A2. Otani occupied the gunner position of the second Sherman, and opened fire on the third tank. Due to the blind spots and lack of visibility of the Sherman as reported by the 4th Tank Battalion, Otani managed to make his move without worry of counter fire. Firing the 75mm cannon, he was able to successfully disable the last Sherman. By this point the marines had already gotten to the field and began to engage the Japanese position. Otani managed to exit the sherman, and return to safety as his comrades provided fire support.


Only Known Photograph of the Engagement
with Otani and the Shermans, by American troops.
 His actions gave his fellow troops exceeding morale, and forced the 21st Marines to plan another route of attack. The marines decided to launch a night assault on the Hill, something the Unites States hadn’t done during the Pacific Theatre. On the midnight of March 6th, the 21st’s attack was a success, as most Japanese troops ended up sleeping, unexpecting the American marines to attack under the moon. Once aware of the marines’ actions, the Japanese began engaging the American infantry to desperately protect the Hill. The night assault had been a resounding success, and on the dawn of March 7th, left the already dwindled Japanese even smaller in number. Their morale battered, the tides turned again in the Marines favour.

Aftermath

The Sherman model Otani Captured.
Still residing on Iwo Jima.
It has become a tourist attraction. 
By March 9th, the Unites States’ 21st Marines managed to successfully capture Hill 363c from the Japanese. The American forces during the engagement lost a total of 827 troops. The battle report lists 4 missing in action, likely had being the Sherman crew the Japanese engaged after bailing from their tank whom Otani had damaged. Not long after the battle for Hill 363c, Japan had officially surrendered the Island to the Unites States. Just over 200 Japanese troops had surrendered. Second Lt. Otani Michio had been one of them, and was recognized as a hero by his comrades.

He was regarded as a war hero once he and fellow prisoners returned home when the war had finally ended in September of 1945. Due to his actions not reaching home until the war's end, he was never officially recognized for his feats in battle. The tank he managed to occupy remains on the island today, as a monument for his actions on the 6th of March, 1945.



Hello everyone. Finally I've been able to finish and post this historical article! Hopefully now that this is done, I can also get other projects finished so I can share them here. I'll plan on doing a tank article next to get back in the cycle, and yes... I haven't forgotten the O-I series with Part 3, its coming soon!