Type (designation)

The word Type followed by a number is a common way to name a weapon or product in a production series, similar in meaning to "Mark". "Type" was used extensively by the Japanese and Chinese militaries beginning in the 1920s, and is still in current use by the militaries of both nations. The United Kingdom uses a type number system for much of their military equipment. Many other nations use the word "Type" to designate products in a series.

The Imperial Japanese Navy (IJN) began using the Type-Number System in 1921 to designate aircraft accepted for production. The numbers used after the word "Type" were based on the number of years that the Emperor Taishō had reigned. Since his reign began in 1912, an aircraft ordered into production in 1921 would have been called "Type 10", the tenth year of the emperor's reign. At the end of 1926, the emperor died, leaving his son Hirohito as the Emperor Shōwa, and the numbering system was reset to mark the new emperor's reign.

In 1929, the government of Japan adopted a new system based on the imperial year. Aircraft ordered for production from 1929 onward were assigned the last two digits of the year marking the continuity of Japanese emperors. 1929 was the 2589th imperial year, so aircraft ordered that year were designated "Type 89". 1940 was the 2600th year, and the IJN numbering system was reset to single digits. New aircraft were designated 0 (zero). The well-known Mitsubishi A6M Zero was ordered into production in 1940 as the IJN "Type 0 Carrier Fighter" (Rei shiki Kanjō sentōki, 零式艦上戦闘機), and was popularly called the "Zero" because of its type.

In 1943, the designation system was abandoned by the IJN as it was considered too revealing about the nature of the aircraft. In its place, the aircraft were named with popular terms such as Kyōfū (強風 "Strong Wind") for the Kawanishi N1K introduced in 1943.

The Imperial Japanese Army (IJA) began using the Type designation system in 1927, for all weapons, vehicles, military equipment, subassemblies and subsystems such as engines and gunmounts. In 1940, instead of resetting to zero, the IJA assigned "Type 100" to equipment put into production that year. In 1941, the IJA reset to "Type 1". Unlike the IJN, the IJA continued to use the system through 1945 with the production of the Kawasaki Ki-100 Army Type 5 Fighter.

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