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Attitudes to the war
Nomenclature of the Japanese submarines in the Sydney attack
Identification of the mother submarines that carried the midget submarines to Sydney followed the Japanese system and started with “I” (in Japanese pronunciation, /i/, not /ai/). Thus, both Australian and Japanese use the same identification numbers. In contrast, identification of midget submarines can be extremely confusing as each vessel was called something different in Japan and Australia. Under the Japanese system, the midget submarines were Ha-14, Ha-21 and Ha-24. Each submarine had an identification number marked on the side of the hull. Thus, the hull on display at the Australian War Memorial carries the number 21.

In the Australian system, however, each midget submarine inherited the number from its mother submarine. Thus, MATSUO’s submarine, which was launched by I-22, was identified as M-22 and similarly, CHUMAN’s as M-27. Identification for BAN’s was more confusing because his submarine was initially going to be launched from I-28, but I-28 was sunk just before the operation. For a while BAN thought his mission was cancelled because he did not have a mother submarine to carry the midget from Truk to Sydney, but a midget submarine which was initially carried by I-24 had a serious accident in which a crew was killed and the commanding officer was injured. Subsequently, BAN’s midget was loaded on the I-24 but retained its original number M-28 and joined the Sydney operation. The Australian War Memorial follows the convention of numbering the midget submarines according to their original mother submarine.

However, in recent years, there seems to be a change in the numbering system. When BAN’s submarine was finally located outside Sydney Harbour in 2006, Tim Smith, a marine archaeologist, submitted a comprehensive survey report on the wreck for the Heritage Office of Department of Planning of the New South Wales government. (
In this report, Smith referred to BAN’s midget submarine as M24, not using the original Japanese identification of Ha-24, but simply because it was launched from I-24.

On this site, instead of using the numbers, the midget submarines are identified by the commanding officers’ names in order to avoid confusion.

Mother submarines:

I-22 (carried Matsuo’s sub)Commander AGATA Kiyoshi
I-24 (carried Ban’s sub)Commander HANABUSA Hiroshi
I-27 (carried Chuman’s sub)Commander YOSHIMURA Iwao
I-29 (carried a float plane)
I-21 (carried a float plane)Commander SASAKI Hankyu

Midget submarines:

Names of crewAustralian IDJapanese ID
MATSUO Keiu and TSUZUKU MasaoM-22Ha-21
CHUMAN Kenshi and OMORI Takeshi M-27Ha-14
BAN Katsuhisa and ASHIBE Mamoru M-28 or M-24Ha-24

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