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Japanese Designation Systems

The Imperial Japanese Army (IJA) and the Imperial Japanese Navy (IJN) used several designation systems which differed only marginal for land-based weapons (compared to the airforce and naval designation systems). Most designations had the same basic appearance:

Yeartype - sort of equipment - (not always) short designation - (not always) additions

A) Yeartype

The Yeartype consisted mainly of a number indicating the year of introduction or design begin and the syllable "shiki" for "Type" or "Model" (which is still not finally clarified among experts, most tend to "Type").

Until 1940 the year was used in which the weapon system was officially introduced (e.g. Type 95 Light Tank) or finally refused (e.g. Type 95 heavy tank). From 1941 on this system was not longer used that strictly, mainly to hamper enemy intellicgence (e.g. the Type 3 medium tank was introduced in 1944, design was started in 1943).

If there are different weapon systems of the same type introduced in the same year the supplement "model" and a number was added. (e.g Type 94 Model 1 - 4 for four different sized radio sets). Changes in the design of a particular "model" was indicated by the further addition "Mark" and number (eg. Type 94 Model 2 Mark 3 bomb fuze).

For the year of introduction two different calendar systems were used:

a) Imperial Calendar

With this system the additional syllable "nen" = "(regency) year" was added between year and "shiki". The year is given as "Year of regency" of a particular emperor:

Meiji regency: Emperor Mutsuhito (1852 - 1912), regency 1867 - death 1912
1867 was Year 0, 1912 was Year 45 of Meiji era. So any weapon introduced in this era received the year- designation Meiji (e.g. the famous Arisaka rifle introduced in 1905 was designated Type Meiji 38 rifle, the 24 cm howitzer introduced in 1912 was designated Type Meiji 45 howitzer...)
Taisho-regency: Emperor Yashihito (1879 - 1927), regency 1912 - death 1927
1912 was Year 0, 1927 was year 15 of Taisho-era. Any weapon introduced in ths era after the death of Mutsuhito received the year-designation Taisho (e.g. the light 37 mm infantry gun introduced in 1923 received the designation Type Taisho 11 infantry gun...)
Showa-regency: Emperor Hirohito (1901 - 1989), regency 1925 (from 1923 inofficially, from 1925 officially as co-emperor to aid the very ill Emperor Yashihito) - death 07.01.1989
1925 was Year 0, 1989 Year 64 of Showa-era.

To simplify the designation system and to reduce irritations if the Regency addition wasn´t added completely (e.g. if only "juichi nenshiki" = "Type (regency) year 11" is mentioned it could mean a 1923 = Taisho 11 or 1936 = Showa 11 introduced weapon system) IJA and IJN changed from regency year to Jimmu-calendar year in 1928.

But many navy and airforce design orders were designated after the Showa-calendar (e.g. The design of the A6M "Zero" started as "Navy experimental 12-Shi Carrier Fighter" in year 12 of Showa regency = 1937.)

b) Jimmu-Calendar

The Jimmu-Calendar is based on the more or less mythical beginn of the japanese empire. In 660 BC (in 1872 the 11. February was declared as "correct date") a local leader defeated the last larger local enemy and founded the japanese imperial dynasty. He later received the honor name Jimmu. For more informations click here. So the standard japanese calender which is still in use began in 660 BC.

From 1928 on IJA and IJN designated their weapon systems using the Jimmu-Calendar-year. 1928 was year 2588. To simplify this system only the last 1 or 2 ciphers were used (2588 = 88, 2604 = 4). For 1940 the possible year designations 0 and 100 were both taken (IJA used 100, IJN 0).

B) Sort of equipment

In general the same designations as in western armys were used, translated into japanese language (e.g. light tank, rifle, handgrenade, radio set, gas mask etc.). Sometimes designations were somewhat different but more or less self-explanatory (e.g. "Ju-Sokosha" = "heavily armoured vehicle" for the small Type 92 recon tank used by cavalry units; "recoilless rifle/gun" for rocket-propelled at-weapons and artillery rocket launchers, IJA did not have real recoilless rifles/guns; "kikanho" = "automatic cannon" for light aa-guns).

C) Short designation

Several japanese vehicles received short designations. Some of these designations were part of a system (e.g. light and medium tanks, gun tanks etc.), others had to do with the intended tasks (e.g. special tractor, gun carrier, armoured vehicle etc.) or were added during development and officially adopted later (e.g. "Ha-Go" or "Ka-Mi") Some meanings were lost during the years but most are still known. I will cover this topic in a later post here.

D) Additions

Several pieces of equipment received additions to clear the identity of the piece of equipment. Often used were the following:

KAI (short for "Kaizo" = "modified").
This was added if major modifications were made without changing the complete system (e.g. Type 97 Medium Tank Chi-Ha KAI for the Type 97 armed with the Type 1 47 mm tank gun in a new turret, major upgades on aircraft models etc.).
Alphabetic characters
Another system to mark major changes without changing the complete system (similar to the german system, e.g. Panzer III F, G, H etc.). IJA used the first letters of the traditional (chinese) alphabet:
  • Kou = A
  • Otsu = B
  • Hei = C
  • Tei = D
  • Bo = E
  • Ki = F
  • Kou = G (same pronunciation as Kou(A) but different character)
These additions were mainly used for vehicles (e.g. Kou(A) for the gasoline engined version, Otsu for the Diesel engined versions).

Nicknames
Several weapon systems received nicknames officially, mainly aircraft. Other nicknames were adopted officially after beeing used for some time inofficially by the soldiers (e.g. "Reisen" for "Rei Sentoki" = [Type] 0 fighter)
Numerations
several vehicles received numerations meaning "first of this kind of wepon". The numerations were basically alphabetic or numeric characters followed by "gata" = "of this kind" or "go" = "version" (e.g. "Kou(A)-gata" = first of this kind ", here light tank, for the Renault FT-17 tanks, "Otsu-gata" = second of this kind" for the Renault NC-27 light tanks, "I-go" = "first version" for the type 89 medium tank or the Type 98 mini-engineer vehicle). This was even used as designation of the Army guided air-to ground missile development (I-Go-1)
Others
Sometimes additions were used only inofficially but taken over by allied forces and used in literature as "official" (e.g. "Shinhoto" = "new turret" as nickname for the modified Type 97 medium tank with the 47 mm gun in a newly designed turret)

Further Reading