Stories and Battle Histories of the IJN's Converted Transport Fleet

22 August 2018

By Berend van der Wal, Gilbert Casse and Peter Cundall

with Bob Hackett

Discussion & Questions

(CHOKO MARU prewar)

Prior to and during the Pacific War, the Imperial Japanese Navy enlisted some of Japan's merchant fleet's cargo, passenger-cargo ships and liners. They were converted to military use and became Tokusetsu Unsosen Kyuryosen, (Converted Stores Ships), used to transport fresh food to other ships and advanced bases. Between 1941 and 1945, thirty six Kyuryosen were employed by the IJN. Other ships were also requisitioned by the IJN but not enlisted. They were called Ippan Choyosen (General Requisitioned Ships) and manned by civilian crews. IJA and the civilian shipping administration requisitioned many other ships.

To summarize, during the war employment of ex-merchant ships was divided into three main administrative categories:
A = requisitioned and operated by the Japanese Army and named Rikugun Yusosen (IJA Transports). They include Cargos, Passenger-Cargos, Liners and Tankers.

B = requisitioned and operated by the Japanese Navy with civilian crew (captain often being Navy Reserve). These are named Ippan Choyosen.

C = controlled and operated by the Senpaku UnŽeikai (Civilian Shipping Administration).

X = requisitioned by the IJN and converted into armed Naval Auxiliaries with IJN crews (gunboats, minesweepers, etc.) and named Tokusetsu Kansen followed by another suffix for the ship’s use.

Beside the above categories, there were many shared employments Army/Civilian (A/C) and Navy/Civilian (B/C). These ships were respectively called Rikugun Haitosen and Kaigun Haitosen. Normally, this meant that the vessel on its outbound journey was under Army or Navy control carrying troops, military supplies, etc. and on its return voyage was carrying cargo for the benefit of the civilian owner of ship. While used by the Army, the Haitosen also received Army transport numbers like Army requisitioned vessels (A). Employments by Army or Navy could also be expanded, meaning that the ship was used by Army/Navy for one full turn (outward and homeward voyage) or even a series of voyages.

This page will cover the activities of the thirty six IJN Converted Auxiliary store ships and some Ippan Choyosen.

IJN Converted Storeships : Tabular Records of Movement (TROMs)

(Classes link to specifications summaries)


Sapporo Maru
(posted 2 August 2017)

Azuchi Maru
(posted 2 November 2017)

Mamiya Maru
(posted 2 December 2017)

Teshio Maru
(posted 10 January 2018)

Kitami Maru
(posted 1 February 2018)


Haruna Maru
(posted 30 June 2018)

Choko Maru
(posted 2 June 2018)

Manko Maru
(posted 2 April 2018)

Chichibu Maru
(posted 2 May 2018)

Hoko Maru
(posted 1 July 2018)

RAMB I Class

Ikutagawa Maru
(revised 30 January 2017)


Kitakami Maru
(posted 1 May 2014)

Oi Maru No. 2 Go
(posted 2 October 2017)


Banshu Maru No. 2
(posted 2 September 2017)

UNKAI MARU No. 3 Class

Unkai Maru No. 3
(posted 2 September 2017)


Banshu Maru No. 3
(revised 9 December 2017)


Banshu Maru No. 5
(posted 2 November 2017)

BANSHU MARU No. 16 Class

Banshu Maru No. 16
(posted 2 December 2017)

BANSHU MARU No. 18 Class

Banshu Maru No. 21
(posted 5 March 2018)


Koa Maru
(posted 22 August 2018)

Bibliography of Sources

About the Authors

Mr. Berend van der Wal got interested in the Japanese Navy through his hobby ship modelling. He researches the Japanese Navy since 1978. He is an IT support engineer and resides in the Netherlands.

Mr. Gilbert Casse is a maritime historian and researcher. Retired from the aerospace industry, and later from managing Le Mans racing cars and drivers, his advocation is ship modelling, maritime photos and paintings. He resides on the SW coast of France.

Mr. Peter Cundall is a maritime historian and researcher who specializes in merchant ships and convoys. He resides in Australia and works in the maritime industry.

Mr. Bob Hackett is a military historian and researcher. Retired from the United States Air Force and later from the aerospace industry, he resides in Florida.

Questions to the authors concerning these TROMs should be posted on the Discussion and Questions board.