Probably the most famous Japanese heavy tank is the O-I, a 120 ton multi-turreted gargantuan monstrosity. There is something appealing to it to say the least. But maybe it was actually 140 tons. There reflects the difficulty about this tank.
To get started, I find it might be helpful to draw out the full extent of Japanese heavies. It could help put things in perspective. So real quickly, here is a list of all Japanese heavy tanks possible for WoT with a few handy facts for each. All are multi turreted except for the noted Heavy X which I do not know anything about. Armor is listed in a front/side/rear format if the numbers are available. Otherwise just the maximum armor is given. The 100 ton and the O-I will be discussed afterwards.
Based off Japan’s very first tank, the Experimental 1 tank.
炮塔装甲: 30/25/25 车身装甲: 35/30/25
Improved firepower via forward mini-turret mounting a 37mm cannon. Improved armor and suspension redesigned.
建造日期: 1940年 (没通过机动性测试)
重量: 100 tons
发动机出力: 550马力 x2 总计 1,100 马力
装甲: 车身正面: 150mm 车身侧面: 70mm
Top secret project initiated right after the Japanese suffered defeat from the Soviet Union in 1939.
建造数量: 1 (要么是造好了或者是没造好的原型车)
建造日期: 与1944年开始,计划持续时间长度不明. 有可能持续到了1945年8月
重量: 120 或 140 吨
发动机出力: 550马力 x2 总计 1,100 马力
炮塔装甲: 200/200/200 车身装甲200/110 或者部分装甲区域厚度 75 以及其他部分 35/150
Probably intended for Manchuria.
WG stated that a tank for tier 10 has been found. It was stated as huge and massive but still not heavier than the Maus. There is no official name that I know of.
The information that follows comes from multiple sources. The core parts all match but there are some inconsistencies. It is difficult to say which is true or false. The facts in the sources are mostly from what was described by those involved or on rumors. There are very little primary sources available like photos or complete original blueprints that could enable more consistency on available information. However Suzuki from Finemolds does have a collection of primary sources on the 100 ton tank. Aside from Suzuki, the other sources themselves often indicate how some history or technical details are speculated and remain unconfirmed. Some sources present information not giving in the other sources. So here will be a list of the sources along with reference abbreviations in parenthesis so that the reader can know where each bit of information is coming from after a little familiarization. I am afraid that while very interesting, reading this might be difficult to grasp at first because of all the different sources.
以下信息的来源渠道很多。 最重要的部分是一样的， 但是依然有一些矛盾的地方。很难说那是对的还是错的。信息的来源基本就是从那些参与了该项目的人得到的，或者是一些流言。原始文献，例如照片和可以对现有信息进行统一的原来的蓝图的数量很少。然而Finemods（一个日本模型网站，或称ファインモールド——译注）的“Suzuki—铃木（暂称）”的确拥有一整套关于百吨的原始文献。除了铃木之外，其他的文献通常都表明了有些历史性和机械的细节部分都是推测，或者是未经确认的。有些文献中的信息在其他文献中并没有被提到。以下是一个文献列表，它们名字简写都会放在名字后面的（括号）中，读者可以在一段时间的熟悉后更加顺畅的阅读这篇文章。尽管这些东西很有意思，但是由于消息来源的多样性，一开始有可能还是很难理解。
Pacific War Secrets: All Japanese Secret Weapons (JSW)
Imperial Japanese Army Land Weapon Guide (LWG)
Tank and Tank Battles (TTB)
Japanese Tanks (Hara – The primary author)
Suzuki’s pictured sources (Suzuki – Has the only primary sources from what I understand and thus likely to be the most accurate of all. Well, there could be more primary sources that are still being held secretly)
The Phantom 100 ton Super Heavy Tank
Below is from a section in TTB unless stated otherwise.
The writer of this section is Shigeo Otaka who was a Mitsubishi engineer involved in the 100 ton tank’s development. He states that in this section he applied information from other people involved in the project but due to the passage of time and the secret nature of the military program, he is unable to give a complete description of the tank. The description is made only from collective memories of those involved however the main features can be described.
这一段的作者是Shigeo Otaka，曾经参与过百吨开发的三菱的工程师。他在这一段中表示他把其他同样参与了这个计划的人嘴里的信息也谢了出来，但是鉴于时光流逝， 以及军方计划天然的保密性，他无法给出对坦克的完整的描述。描述都是基于记忆而写的，然而主要的机能还是可以被描述出来的。
The project was under the supervision of Colonel Murata from the 4th Technical Research Head Quarters. JSW says that Colonel Iwakuro from the Department of War gave the order to build the monster. The order to build the 100 ton tank came immediately after the defeat against the Soviet Union in the Nomonhan incident in 1939. LWG gives a quote from a position and ranked officer that is the same as Colonel Iwakuro but does not gave the officer’s name. Probably still Iwakuro. Quote and picture of Iwakuro below.
“I want a huge tank built which can be used as a mobile pillbox in the wide open plains of Manchuria. Top secret.”
Here is another quote from LWG of an undisputable requirement from the Colonel.
“Make the dimensions twice that of today’s tanks.”
Shigeo Otaka and several others were guided multiple times throughout a wooden barracks that used to be the headquarters of the 4th Technical Research Group, sometimes crammed together in small rooms. Under strict rules to speak of nothing of what will be seen, the group of people was finally led to a secret room. The room had a two door entrance to reduce the chance of eyes catching a glimpse of the interior. Nobody outside of the room knew what was going on. Here, the plan was pulled out in lots of random pieces. It was an effort for the group just to bring all the pieces together but eventually the secret tank image appeared. There were some concerns whether the tank would be able to move or how it could be transported but those concerns were kept individually private. However, the behemoth was both imposing and impressive.
Shigeo Otaka以及其他人被许多次的带过一个木头兵营，就是曾经的第四科技研究组的总部，有时候他们会挤在一个小房间里。 在下达了不要说出任何所见之物的命令后，这群人最终被领到了一个秘密房间中。这个房间有两道门，以防止从外部可以偷窥到房间内部。房间外面的人完全不知道里面发生了什么。在那个房间里，计划被分成了许多随机的小块。这是为了让整个小组的所有人把那些小块都带到一起，最终可以让坦克的图像显现出来。曾经有过对于坦克是否可以移动或者如何运输坦克的疑问，但是那些疑问最终还是个人的疑问。然而，这个钢铁巨兽依然是非常的惊人。
Total length was 10 meters. Total width was 4.2 meters, and total height was 4 meters. Height without the turret was 2.5 meters. Track width was 900mm. The power plant was two 550 horsepower air-cooled gasoline engines for a combined horsepower of 1,100hp. Top speed was 25kph.
This section from the TTB writes that the army called it the O-I and Mitsubishi called it Mi-To (Mitsubishi-Tokyo). Hara, JSW, and LWG call only the 120 ton tank the O-I so TTB could be mistaking here. JSW and LWG say the O-I was called Mi-To and not the 100 ton tank. Hara does not mention “Mi-To” but does say that both the 100 ton and the O-I were developed by Mitsubishi. Perhaps both were actually called Mi-To. At least according to Hara, the “Mi” part is true for both. Maybe both were also made in Tokyo. JSW says that according to one rumor, that when the O-I was completed, it was disassembled at Mitsubishi Heavy Industries Shimo Maruko factory to be shipped to Manchuria. Shimo Maruko is in Tokyo. It seems to me that both the 100 ton and the O-I were called Mi-To.
Perhaps, and this is again pure speculation I am going to interject here, but perhaps do to the terrible failure of the mobility test (which you will soon read) led people to forget using the O-I name for the 100 ton due to its fail. The naming convention that the O-I was from was in effect at the time the 100 ton was in development. If all testing was successful, perhaps the 100 ton would have become the O-I which would mean the 120 ton would have to become the O-Ni.
Anyway, continuing on with the TTB 100 ton tank section…
The two engines were placed length-wise parallel to each other in the rear section of the tank. Both engines were used at the same time which made it difficult to use. The structure of the transmission was the same as the Type 97 Chi-Ha however the gears were heavy. The 5-speed forward gear lever was in center front of the driver and both hands were used to adjust the lever. The tank was rear-wheel driven. The engine, driver, and transmission layout is illustrated in picture 1 a couple of paragraphs down.
The design of the suspension in picture 2 used coil springs. Each side of the tank used 3 of these 4-wheel sets for a total of 12 road wheels per side. The drawings from Suzuki have 8 wheels which would mean 2 sets, not 3 sets per side. Other artist impression drawings also have 8 wheels and a few have 10 wheels. In my opinion, 8 is most likely to have been the case. The road wheels had no cushion like rubber at all. The hard metal wheels contacted directly with the tracks.
All the armor was made with soft steel. Some other Japanese prototype tanks have also been made with soft steel such as the Type 4 Chi-To 57mm cannon prototype in 1944. The front was 75mm thick with an additional 75mm thick plate stuck on for a total thickness of 150mm. The side hull was 35mm thick. Over the side hull and over the suspension were side skirts with a thickness of 35mm bringing the total side armor thickness to 70mm. The side hull armor and side skirt armor is illustrated in picture 3.
It was easy to stand within the interior of the tank and there were even paths throughout the vehicle. The driver’s compartment, central fighting compartment, and engine room were separated by 16mm thick walls.
There was no window for the driver and thus used a periscope instead. Aside from the gear lever and the accelerator, everything else was hydraulic which made it easy to drive.
For testing, it was shipped to Sagami Armory. Only the people involved in the development of the tank did the transporting and it was a major ordeal. The tank was covered with awning and shipping started at 2:00am at night and ended when night was broken by the sun. Transportation took 10 days. Sagami Armory was located in Kanagawa which is adjacent to Tokyo giving more support to the idea the 100 ton tank was in fact built in Tokyo thus having the name “Mi-To” plausible.
On the day of testing, Colonel Murata was called to the battle front so in his place for observation was Lieutenant Colonel Nakano. The chief of Sagami Armory was also there, Tomio Hara himself. The ground at the location was quite soft so during off-road testing, as the tank drove, its treads sank into the ground by a meter. Vehicle rotation would also cause the tank to sink. Perhaps due to stiff coil spring cushioning, the road wheels came out. That canceled the test. On a concrete road, bits of both tracks came out and the concrete was ripped. After test, a full bow with both hands to the ground was made to the repair department chief and that put an end to the 100 ton tank. It was covered with awning again and left there until 1944 when it was finally scrapped.
Another section in TTB contains an interview with four Mitsubishi tank engineers during the Imperial Japan era. Below is a picture of them.
Information from the interview feels a little vague but some additive bits are described here. Two turrets were lined up (mini-turrets in the front I assume), top speed was 40kph (begs for some skepticism if I may say so), and armor was 100mm. There is no existing photo. It was a top secret project under military order. There were many pains regarding issues like whether or not to make it lighter, to make it roomier inside, and to cut down on complexity.
Hara described the 100 ton as the following. In 1940 a 100 ton super heavy prototype was built. Its outside appearance resembled the Type 95 heavy tank. The main armament was a 10cm cannon (meaning 105mm cannon most likely. There is no source that specifically says what 10cm cannon was used. The Type 92 is the likely case but maybe it could have been something else). Mini-turrets were present on both the front and rear of the tank. The number of mini-turrets is not described. The suspension type was coil springs and the tank was camouflaged. The tank was tested but failed and thus later was destroyed.
Suzuki shows three mini-turrets. Two lined up in the front and one in the rear. His pictures below.
LWG says that the 100 ton tank hull was completed and underwent testing. Despite the fairly detail account provided by TTB, no turret details were giving. So it seems very likely that the 100 ton tank was tested without the turret (or turrets).
A shrine in Japan called the Wakajishi Shrine has (or had) on display a very large track link. Suzuki stated that while the link seems like it belongs to the O-I, it’s more likely that it belongs to the 100 ton tank. The track link has the same shape as a Chi-Ha but just much larger. It is so heavy that 1 man cannot lift it. The width is about 800mm and the pitch is about 300mm. Here is a link to the webpage with the track link at the bottom of the page (also below) and what is described in this paragraph in the Japanese text right of the track link picture (source:Wakajishi shrine page)
日本的若狮子神社（曾经提到过，位于日本静冈县富士宫市，2013/08/15 QA中出现过——译注） 展示了一块（或者说曾经展示过一块）非常巨大的履带的一片。Suzuki表示尽管那个履带片看起来很像是O-I的履带片，但是它更像是百吨的履带。这个履带片的形状与九七式中战车チハ很像，但是大很多。它也很重，一个人是拿不起来它的。宽度大约是800毫米，沥青大约300mm厚。以下是一个链接，会将你重定向到神社的页面，页面最下方是这张履带的图片（即下图），在图片的右侧是以日文写就的说明性文字。（来源：若狮子神社）
The O-I Monstrosity
In the name “O-I” (pronounced as oh-ee), the “O” means big, or in tank lingo, heavy, and the “I” means “one” or “first”. So it means “First Heavy”. Many Japanese tanks comply with this naming convention. If the O-I was ever completed, it would have received a “Type” designation in the front. Anyway…
Below is a description from Hara.
In 1944, there was a plan for a 120 ton tank named “O-I”. The main armament in the central turret was a modified Type 92 10cm cannon. Two mini-turrets were lined up in the front hull in a way that the mid-point of the two turrets was slightly left from the mid-point of the tank. One armed with the Type 1 47mm tank gun and the other armed with a Type 97 7.7mm tank heavy machine gun. In the rear portion of the tank, there was a machine gun turret with two 7.7mm machine guns. That makes a total of 4 turrets. 200mm thick heavy armor was giving to the tank. The suspension was of coil springs. The power plant was two modified aircraft air-cooled BMW gasoline engines which gave a total of 1,100 horsepower. Top speed giving is 25kph. Length, width, and height, are 10 meters, 4 meters, and 4.2 meters respectively (LWG puts the length at 11 meters). Track width giving is 750mm (which is a little surprising as it is somewhat slimmer than what is giving for the 100 ton tank). This same modified engine was also loaded in the Type 5 Chi-Ri medium tank. Like the 100 ton tank, the project was giving to Mitsubishi but due to the war situation, the project ended before its completion.
Type 92 105mm cannon was an L45 and had a muzzle velocity of 765m/s. It was widely used by the Japanese as a field cannon. Maximum range was 18,200 meters.
A reason for building the O-I is giving by LWG. By 1944, the war situation for Japan has become desperate. Some information about super heavy tank development in Germany has come to Japan and that rekindled the idea for a super powerful tank. Thus development restarted on a new super heavy which was called the O-I. It was 120 tons and had 3 or 4 turrets. In the picture below also in LWG, the rear machine guns are coming out of gun ports on the main turret rather than in a 4th mini-machine gun turret mounted in the back like Hara said.
It is generally thought that it was never completed however there is one testimony saying that it was completed and that it weighed 140 tons. Some rumors say that it was completed and then disassembled for shipping to Manchuria.
For World of Tanks
From the readings here, nothing indicates that there were multiple designs for either the 100 ton or the O-I but there are several interpretations. That is not to say with great certainty that there were no multiple designs but it seems unlikely. Tier 10 is the heavy X. So that leaves tiers 9 and below. The Type 95 heavy tank is hardly tier 4 quality. So if saying we wanted to start at tier 5, the 100 ton tank and the O-I would need to fill up tiers 5, 6, 7, 8, and 9. This might require some liberal use of different interpretations in order to create 5 different tired tanks.
An easy pick up is removing the 35mm side skirts and the 75mm front armor slab from the 100 ton so as to create a lighter low armored “100 ton” with 75mm front armor and 35 side armor at tier 5 and then have a tier 6 “100 ton” with its full complement of armor.
For tiers 8 and 9, one way could be to have the tier 8 O-I be the 120 ton version and the tier 9 be a 140 ton version with a little more armor. I am not sure how the WG player base would feel about creating different tiered tanks based off of different interpretations. It could simply be seen as taking one tank and stretching it across two tiers like we see with the French AMX-13. But in the case, for the O-I, some different interpretations could be applied which would be better than WG magic in my opinion. But for whatever is at tier 8 and 9, new cannons will be needed. The 105mmL55 cannon originally meant for the Ho-Ri TD is an option. And there are naval cannons available as well. In whichever way this will be handled, there is plenty of time to research more and ponder over it since current news feeds about WG developments indicate that a Japanese heavy line won’t be added until as far as 2015.
对于8级和⑨级的话，有一种解决办法是把120吨的O-I放在8级，140吨的在加强一下装甲之后放在⑨级。我不确定WG的玩家群体对这种把不同坦克的不同配置放在不同等级上会怎么看。 它也有可能只会被单纯的认为是把一辆坦克硬生生的分成两级，就像法国的AMX-13一样。但是在O-I这个车上，我觉得车辆本身不同的配置会比WG自己瞎搞好很多。但是8级和⑨级的无论什么车都需要一杆新炮。105mm L55炮（并非九二式十糎加農砲，该炮倍径为45）本来是给ほり这辆TD用的。（ほり：是五式中戦車 チリ的一辆变种，使用了上述的105mm炮，有可能是受到了德国的费迪南/象式的影响，但是从来没有生产过原型车。——译注）而且还有军舰炮可以拿来用。无论这个问题如何得到解决，现在还有大把的时间可以去搜索资料以及仔细思考到底应该怎么做，因为现有的新闻表示WG的开发团队表示日系重坦线在2015年之前都没戏。
Non-Internet sources. English titles are my own translations.
1. “Japanese Tanks” Hara no Tomio 1978. 日本の戦車 原乙未生
1.“日本的坦克” Hara no Tomio 1978. 日本の戦車 原乙未生
2. “Tank and Tank Battles” 2012 戦車と戦車戦
2.“坦克与坦克战斗” 2012 戦車と戦車戦
3. “Imperial Japanese Army Ground Weapon Guide 1872-1945” 1997帝国陸軍陸戦兵器ガイド 1872-1945
3.“日本皇军地面武器指南 1872-1945” 1997帝国陸軍陸戦兵器ガイド 1872-1945
4. “Pacific War Secrets: All Japanese Secret Weapons” 2008 太平洋戦争秘録 日本・秘密兵器大全
4.“太平洋战争秘密：日本所有的秘密武器” 2008 太平洋戦争秘録 日本・秘密兵器大全
5. “Japanese Ground Cannons: Heavy Field Cannons” Sayama Jiro 2012 日本陸軍の火砲 野戦重砲
5.“日本陆军的火炮：重野战炮” Sayama Jiro 2012 日本陸軍の火砲 野戦重砲