Japanese Tank Nomenclature

Hello everyone,

I will now do an exception and repost an old post from US forums (can’t remember who posted it first, I think it was SoukouDragon) about the way Japanese tanks are named, because I believe that’s an actual topic:

There were Two systems: Order System and Classification System, both of which are under the Army Imperial Year System.

Army Imperial Year System

The Imperial Year was used as the standard for designating the type, based on the mystical founding of Japan in 660 BC. The accepted practice was to use the last two numbers of the year as a type number, as in the Type 89 medium tank of 1929, with Type 100 for items accepted in 1940. After 1940 only the last digit was used, so Type 2 equipment was accepted in 1942.

Order System

Each tank is given a separate name, based on the order in adapation. The Type 89 medium tank was the “I-Go”, or “first car/model” while the Type 95 light tank was the “Ha-Go”, or “third car/model” (no second model has been identified).

Classification System

Starting from the Type 97 Chi-Ha, the naming system was changed to incorporate the classification of the tank. Each tank would get a two letter name, with the first letter standing for the type of tank and the second for the order in which the tanks were developed.

The majority of tanks fell into three categories – Chi, Ke and Ho, or Medium, Light and Gun, with Chi and Ke used as single character abbreviations for Chiu (or Chui) and Kei. There seems to have been a category for Heavy (O, short for Oo), but this is only “confirmed” in the sense that it was the unofficial name given to the 120 ton tank O-I.

The numbering system used was based on the Iroha, a Japanese poem. This used every character from the Japanese syllabary once, and for a long time was used to put those characters in order (in a rather poetic version of the ABC). The first two lines of the poem, transliterated in roman letters, ran:

i ro ha ni ho he to
chi ri nu ru wo

If we summarize the naming system:

Chi: Medium
Ke: Light
Ho: Gun (Tank Destroyer)
O: Heavy

1- I or Yi
2 – Ro
3 – Ha
4 – Ni
5 – Ho
6 – He
7 – To
8 – Chi
9 – Ri
10 – Nu
11 – Ru
12 – O or Wo

Using the medium tanks as an example:

Chi-I (Medium First): None (most likely Experimental Type 1 Tank)
Chi-Ro (Medium Second): Type 89 I-Go
Chi-Ha (Medium Third): Type 97 Chi-Ha
Chi-Ni (Medium Fourth): Type 97 Chi-Ni (never got out of prototype status)
Chi-Ho (Medium Fifth) Type 98 Chi-Ho (never got out of prototype status)
Chi-He (Medium Sixth): Type 1 Chi-He
Chi-To (Medium Seventh): Type 4 Chi-To
Chi-Ri (Medium Ninth): Type 5 Chi-Ri
Chi-Nu (Medium Tenth): Type 3 Chi-Nu

19 thoughts on “Japanese Tank Nomenclature

      • Kai basically means “changed”or”modified“
        while Otsu means “the second”,so in tank trees, “xxxx Otsu” just means “the second edition of xxxx”, usually you can expect somekind of improvement from the original ones,but not guaranteed

    • It’s based on the Ten Celestial Stems. They’re are still commonly used nowadays in East Asian counting systems similar to the way the alphabet is used in English.

      Japanese version

      Kou = A, Alpha
      Otsu = B, Beta
      Hei+ C, Gamma

    • “Otsu (乙) can mean a few things.It can mean ‘the latter’ when used in a sentence properly. It can also mean strange, witty, chic, and even tasty. The most common use of otsu though is used as slang and means thank you, goodbye, and sometimes but rarely hello.”

      I would actually bet on “hello” because of it being the early tank in Japan.

  1. Chi-I (Medium First)=Type 89 I-Go Kō 八九式甲
    Chi-Ro (Medium Second): Type 89 I-Go Otsu 八九式乙
    And japan didn’t use Chi-Chi so Chi-Ri=Medium Seventh

    Experimental Type 1 Tank through improved will be Type 95 Heavy Tank
    Experimental Type 2 Tank = Type 91 Heavy Tank

  2. Thanks Daigensui, for the original post. It’s neat to see how simply the Japanese labeled their tanks.

    Appreciate you digging it up for the rest of us to look at, SS.

  3. I have a suspicion (a suspicion, speculation, indeed is what I have and what this is) that the Chi-Chi was part of the 3 way medium tank plan in 1942. The 3 MTs were a 47mm cannon MT, 57mm cannon MT, and a 75mm cannon MT. The 47mm cannon MT ended up becoming the Chi-To. The 75mm cannon MT became the Chi-Ri. So that leaves the 57mm cannon MT in the middle. It merged early on with the Chi-To development project.