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Most of the tanks used by the Imperial Japanese Army during the 1930s and 1940s were identified by two complementary designation systems.
The first was used to identify all Army equipment, and consisted of a type number based on the imperial year that the item was accepted. Before 1945 three systems of dating a year were in use in Japan – the Anno Domini system, the era name based on the regnal years of the current emperor, and the imperial year, counting from the then accepted foundation of Japan in 660 BC. In 1873 the Gregorian calendar was adopted, and the Japanese New Year was moved to 1 January. This rather neatly lined up the western and Imperial year systems, so that 1940 became 2600.
Up until 1940/2600 the accepted practise 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.
The second designation system saw each tank given a name, essential to separate between two tanks accepted in the same year. At first the names were simple – 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).
This system was then refined to give each tank 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 respectively, with Chi and Ke used as single character abbreviations for Chiu (or Chui) and Kei.
The numbering system used was based on the Iroha, a Japanese poem first mentioned in 1079. 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
This gave the following number order
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
Light Tanks
Ke-Ni |
Light 4 |
|
Ke-To |
Light 7 |
|
Ke-Nu |
Light 10 |
Medium Tanks
Chi-I |
Medium First |
|
Chi-Ro |
Medium Second |
|
Chi-Ha |
Medium Third |
|
Chi-Ni |
Medium Fourth |
never built |
Chi-Ho |
Medium Fifth |
Type 98 (never built) |
Chi-He |
Medium Sixth |
|
Chi-To |
Medium Seventh |
|
Chi-Ri |
Medium Ninth |
|
Chi-Nu |
Medium Tenth |
Gun Tanks
Ho-I |
Gun First |
|
Ho-Ro |
Gun Second |
Type 4 Ho-Ro |
Ho-Ni |
Gun Fourth |
|
Ho-To |
Gun Seventh |
Type 95 with 120mm |
Ho-Ri |
Gun Ninth |
|
Ho-Ru |
Gun Eleventh |
Type 5 Ho-Ru |