TOKUSETSU UNSOSEN ZATSUYOSEN!

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

19 March 2023

By Gilbert Casse, Bob Hackett and Peter Cundall

Discussion & Questions


(Auxiliary transport BRASIL MARU in wartime by Ueda Kihachiro)


Prior to and during the Pacific War, the Imperial Japanese Navy enlisted some of Japan's merchant fleet's former cargo ships, passenger-cargo and liners. They were converted to military use and became Tokusetsu Unsosen Zatsuyosen (Converted Auxiliary Transports) used to transport troops, military equipment including tanks, weapons, munitions, crated aircraft, parts and stores. Many were also given other wartime roles.

Between 1937 and 1945, 223 Zatsuyosen were employed by the IJN. Several ships were either removed or transferred to other categories before the outbreak of the Pacific War. During the war, 65 ships from other categories were rerated as Zatsuyosen. Other ships were also requisitioned by the IJN, but not enlisted. They were called Ippan Choyosen (General Requisitioned Ships) and manned by civilian crews. The 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 called Rikugun Yusosen (IJA Transports). They include cargo, passenger-cargo, liners and tankers.
B = requisitioned and operated by the Japanese Navy with civilian crew (captain often being Navy Reserve). These are called Ippan Choyosen.
C = controlled and operated by the Senpaku Un´eikai (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 called 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(s) of ship.

While used by the Army, 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 223 auxiliary transports including 13 captured/raised former Allied ships. The 28 Axis (10 Vichy French, eight German, eight Italian and one Finnish) vessels in Japanese service have been covered in our SEMPAKU UNEIKAI SIYOSEN (Government Requisitioned Ships) page.

The Japanese found many and varied roles for their merchant fleet's ex-passenger-cargo ships. Twenty were converted in late 1942 to serve as emergency oil tankers (OHKYU YUSOSEN) and are covered on our extensive YUSOSEN! page. Fourteen such ships were converted for use as armed merchant cruisers and are covered on our TOKUSETSU JUNYOKAN! page, ten others became aircraft transports as covered on KOKUKI-UMPANSEN! Four transports were converted to destroyer tenders and are covered SUIRAI-BOKAN! Nine such ships also became seaplane tenders as detailed on TOKUSETSU SUIJOKI-BOKAN!.

Similarly, another eight transports were converted to submarine tenders and are covered on SENSUI-BOKAN!, ten others became ammunition suppy ships and are on KYUHEIKAN!, six were converted to hospital ships as covered on BYOINSEN, two acted as repair ships as detailed on KOSAKUKAN! and finally, one even became an escort carrier as covered on KIDO BUTAI.






Tabular Records of Movement (TROMs):
IJN Auxiliary Transports
(Classes link to specifications summaries)

NACHISAN MARU Class

Nachisan Maru (revised 24 January 2017)

SENKO MARU Class

Senko Maru (revised 6 May 2018)
Manko Maru (revised 2 November 2018)
NACHI MARU Class

Muro Maru (posted 22 February 2015)

MYOKO MARU Class

Myoko Maru (revised 7 March 2015)
Hakkai Maru (revised 30 April 2010)

KIMISHIMA MARU Class

Kimishima Maru (revised 11 December 2016)

TATSUWA MARU Class

Tatsuwa Maru (revised 23 September 2018)
Tatsuho Maru (revised 19 October 2020)
Tatsumiya Maru (revised 4 December 2016)
Tatsuharu Maru (revised 10 September 2017)

MUKO MARU Class

Muko Maru (revised 27 November 2016)
Naniwa Maru (revised 28 April 2018)



MEITEN MARU Class

Meiten Maru (revised 22 January 2017)
KAIHEI MARU Class

Kaihei Maru (posted 19 August 2011)
Kenryu Maru (revised 20 September 2015)
KOFUKU MARU Class

Kofuku Maru (posted 3 September 2011)
KENYO MARU Class

Kenyo Maru (revised 28 April 2018)

TOYO MARU Class

Kaisho Maru (revised 23 September 2017)
Mitakesan Maru (revised 23 September 2017)
Toyo Maru (revised 14 December 2012)
Kunishima Maru (revised 28 September 2014)
Toyo Maru No. 2 (revised 27 September 2015)
Shinyo Maru (revised 8 December 2013)

NAGARA MARU Class

Nojima Maru (revised 9 June 2017)
Noshiro Maru
(revised 20 November 2010)
GENKAI MARU
Class

Choko Maru (revised 13 September 2015)
Eiko Maru No. 2 Go(revised 21 April 2018)

KINAI MARU Class

Kinai Maru (revised 24 July 2016)
Hokuroku Maru (revised 2 June 2017)
Nankai Maru (revised 2 November 2018)
Hokkai Maru (revised 17 September 2017)
Tokai Maru (posted 22 October 2011)
Sanyo Maru (revised 6 March 2010)

HEITO MARU Class

Heito Maru (revised 29 October 2011)
Shoka Maru (revised 8 December 2013)
Taito Maru (revised 9 June 2017)

CUBA MARU Class

Cuba Maru (posted 5 November 2011)
MIFUNE MARU Class

Mikage Maru No. 3 (posted 5 November 2011)

OKITSU MARU Class

Okitsu Maru (revised 9 December 2017)

SHINKYO MARU Class

Shinkyo Maru (revised 24 September 2020)
Anshu Maru (revised 24 September 2020)
Seikyo Maru (revised 5 October 2020)
Nikkai Maru (revised 5 October 2020)
Rakuto Maru (revised 22 August 2018)

SHOHEI MARU Class

Shohei Maru (revised 22 March 2015)

SHOAN MARU Class

Shoan Maru (posted 2 December 2011)
Meiyo Maru (updated 28 February 2014)
SHINKO MARU Class

Yamagiri Maru (revised 9 June 2017)
Keiyo Maru (revised 8 May 2010)

ASAHISAN MARU Class Class

Asahisan Maru(revised 21 September 2014)
Akashisan Maru (revised 17 August 2018)

KOMAKI MARU Class

Kano Maru (revised 2 June 2017)
KAIKO MARU Class

Kaiko Maru (revised 23 November 2013)

SEIA MARU Class

Nana Maru (revised 31 July 2016)
Toa Maru No. 2 Go (revised 23 September 2017)
KOTO MARU No. 2 GO Class

Koto Maru No. 2 Go (revised 16 August 2013)
Tamashima Maru (revised 2 June 2012)
Kosei Maru (revised 1 December 2013)

AZUMASAN MARU Class

Azumasan Maru (revised 22 January 2017)
Amagisan Maru (revised 21 April 2018)
CHOWA MARU Class

Chowa Maru (revised 23 November 2013)

Nikkoku Maru (posted 7 April 2012)
Nittei Maru (revised 29 April 2017)
Chuwa Maru (posted 5 May 2012)

HAKUBASAN MARU Class

Hakonesan Maru (revised 21 April 2018)

SHOKEI MARU Class

Shokei Maru (revised 22 March 2015)
Nichiei Maru(posted 2 June 2012)

KOSEI MARU Class

Kosei Maru (revised 1 December 2013)

KOGANE MARU Class

Shirogane Maru (posted 7 July 2012)

KINSEN MARU Class

Kinsen Maru (posted 7 July 2012)

KINJOSAN MARU Class

Kimposan Maru (posted 7 July 2012)
PEACETIME STANDARD TYPE (D) Class

Tairyu Maru (posted 4 August 2012)
Nankai Maru
No. 2
(revised 23 September 2017)
Hirotama Maru (revised 19 March 2023)
Tatsutagawa Maru(revised 27 September 2015)
Seizan Maru
No. 2
(revised 11 May 2014)
Shoko Maru (revised 24 January 2017)
Katori Maru (posted 6 October 2012)
Kizugawa Maru (revised 20 September 2015)

SHUNKO MARU Class

Kirikawa Maru (revised 20 September 2015)
Kikukawa Maru (revised 28 April 2018)
Hiyoshi Maru
(revised 17 August 2018)

KACHOSAN MARU Class

Kasagisan Maru (posted 1 December 2012)
HOKUYO MARU Class

Hokusho Maru (revised 13 September 2015)

IKUTA MARU Class

Nagata Maru (revised 19 March 2023)
Yamadori Maru (revised 20 April 2014)

SANTO MARU Class

Santo Maru
(revised 6 May 2018)
Sansei Maru (revised 13 March 2015)

MIKAGE MARU No. 18 Class

Hino Maru No. 3(revised 22 April 2017)



TOEI MARU Class

Toei Maru (revised 2 November 2018)

TENRYU MARU Class

Tenryu Maru (revised 6 May 2018)

Shinryu Maru (revised 8 December 2013)

KOTO MARU Class

Koto Maru (revised 1 December 2013)
NAGISAN MARU Class

Nagisan Maru
(revised 31 July 2016)
Nasusan Maru (posted 8 April 2012)

TARUSHIMA MARU Class

Tarushima Maru (revised 22 March 2015)
Yamafuku Maru (revised 9 June 2017)

KOKAI MARU Class

Kokai Maru (revised 28 September 2014)



SHOKO MARU Class

Shoko Maru (posted 1 June 2013)

KINUGASA MARU Class

Kinugasa Maru (posted 17 July 2005)
Kagu Maru (revised 21 September 2014)

UNYO MARU No. 2 Class

Unyo Maru No. 2(Posted 1 June 2013)
KOSHIN MARU Class

Koshin Maru (posted 1 September 2012)

TONAN MARU No. 2 Class

Tonan Maru No. 2 (revised 17 July 2016)
Tonan Maru No. 3 (revised 6 November 2016)

AKIURA MARU Class

Kozui Maru (posted 24 September 2011)
Fujikawa Maru (revised 8 May 2010)
LIMA MARU Class

Lyons Maru (revised 26 May 2017)
Matsumoto Maru (posted 6 August 2011)



KIRISHIMA MARU Class

Kirishima Maru (revised 30 April 2010)

KAMIKAWA MARU Class

Kimikawa Maru (revised 12 December 2009)
Kunikawa Maru (revised 2 September 2009)
SHOUN MARU Class

Shoun Maru (posted 6/1/2013)

GOSHU MARU Class

Goshu Maru (revised 11 June 2011)
Goyo Maru (revised 8 May 2010)
KOSHIN MARU Class

Koshin Maru
(posted 1 July 2013)
Kogyo Maru (posted 24 July 2010)
Hitachi Maru (posted 25 October 2008)

PEACETIME STANDARD TYPE (C) Class

Imizu Maru
(revised 28 April 2018)

Wayo Maru
(revised 6 April 2018)
Ryuko Maru
(posted 1 August 2013)
Kanayamasan Maru (revised 20 April 2014)
AKAGISAN MARU Class

Akibasan Maru (revised 13 September 2015)
KASUGA MARU Class

Ikushima Maru (revised 17 August 2018)
Kasuga Maru No. 2 Go(posted 1 September 2013)
Shinkoku Maru (revised 31 July 2016)



MIKAGE MARU No. 20 Class

Hino Maru No. 5 (revised 17 September 2017)
Shinsei Maru No. 18
(revised 9 June 2017)

KANSAI MARU Class

Kanto Maru (posted 26 October 2007)
OGASHIMA MARU Class

Ogashima Maru (revised 23 September 2017)

TAIJUN MARU Class

Taijun Maru (posted 1 October 2013)

CANBERRA MARU
Class

Tokyo Maru (posted 11 January 2013)

SANTOS MARU Class

Santos Maru (revised 20 May 2017)
Montevideo Maru (posted 1 November 2013)

KOGANE MARU Class

Kogane Maru (revised 17 August 2018)
ARATAMA MARU Class

Yamashimo Maru
(revised 14 May 2016)



TENZAN MARU Class

Tenzan Maru (revised 31 July 2016)
Senzan Maru (revised 22 August 2018)

KENSHO MARU Class

Kensho Maru
(revised 20 September 2015)

KIYOSUMI MARU Class

Kiyosumi Maru (revised 1 September 2014)

HAKONE MARU Class

Hakusan Maru (revised 2 November 2018)
Hakozaki Maru (revised 2 November 2018)
KEISHO MARU Class

Keisho Maru (posted 1 January 2014)

BRITISH WW1
STD C TYPE
Class

Shoei Maru (posted 1 February 2014)

TOYOSAKA MARU Class

Toyosaka Maru (revised 23 September 2018)

Shinyo Maru No. 8(posted 1 February 2014)

Nissho Maru No. 18
(revised 23 September 2017)

HAKUTETSU MARU No. 7 Class

Hakutetsu Maru No. 7
(posted 1 March 2014)


HAKUTETSU MARU No. 11 Class

Hakutetsu Maru No. 15
(posted 1 March 2014)



HIDE MARU Class

Hide Maru (posted 21 August 2010)

AZUMA MARU Class

Azuma Maru (revised 28 February 2014)
KEISHIN MARU Class

Yoshinogawa Maru
(revised 24 January 2017)

ARGENTINA MARU Class

Argentina Maru (revised 22 April 2017)
Brasil Maru
(revised 2 June 2017)
PEACETIME
STANDARD
TYPE 1E Class

Nissei Maru
(posted 1 April 2014)

SHOEI MARU Class

Fukuyama Maru
(revised 21 September 2014)

NICHIYU MARU Class

Nichiyu Maru
(revised 6 May 2018)



SUWA MARU Class

Suwa Maru
(revised 18 May 2014)
SEIZAN MARU Class

Seizan Maru
(posted 1 June 2014)

RYOTOKU MARU Class

Ryotoku Maru
(posted 1 June 2014)
KAZAN MARU Class

Tozan Maru
(posted 1 June 2014)

YOKO MARU Class

Yoko Maru (revised 14 May 2016)

SHOEI MARU Class

Shoei Maru (revised 6 May 2018)

Shoho Maru (posted 1 August 2014)

HYAKUFUKU MARU Class

Hyakufuku Maru
(revised 17 August 2018)
TOSHO MARU Class

Tosho Maru
(revised 23 September 2018)
Daigen Maru No. 7
(revised 17 August 2018)
UNKAI MARU No. 10 Class

Unkai Maru No. 10
(revised 23 September 2018)
BUENOS AIRES MARU Class

Rio de Janeiro Maru (revised 2 July 2011)

HIKAWA MARU Class

Hie Maru(revised 20 May 2017)
AKAGI MARU Class

Asaka Maru (revised 29 January 2017)

Awata Maru (revised 1 November 2013)
HOKOKU MARU Class

Aikoku Maru (revised 1 September 2014)
Gokoku Maru (revised 1 September 2014)

FUKUEI MARU No. 10 Class

Fukuei Maru No. 10(revised 17 August 2018)
HINO MARU No. 2 Class

Hino Maru No. 2 (revised 30 April 2016)



KOWA MARU Class

Kowa Maru (revised 7 May 2016)

CHOJO MARU Class

Choan Maru No. 2 Go (revised 17 September 2017)
Choko Maru No. 2 Go (posted 1 November 2014)
HIROTA MARU Class

Hirota Maru (posted 1 December 2014)
Yoshida Maru (revised 14 May 2016)
HIYOSHI MARU No. 2 GO Class

Hiyoshi Maru No. 2 Go (posted 1 December 2014)
FUKKEN MARU Class

Busho Maru (posted 1 February 2015)

NISSHO MARU No. 2 Class

Nissho Maru No. 2 (posted 1 February 2015)

NISSHO MARU No. 16 Class

Nissho Maru No. 16 (posted 1 February 2015)
JUZAN MARU Class

Juzan Maru (revised 28 April 2018)



SHINTO MARU No. 2 Class

Iwato Maru (posted 1 March 2015)

TOYO MARU No. 3 Class

Toyo Maru No. 3 (revised 23 September 2018)
NISSHO MARU No. 5 Class

Nissho Maru No. 5 (posted 4 April 2015)

NIPPONKAI MARU Class

Nipponkai Maru (revised 22 August 2018)
ASAHI MARU Class

Asahi Maru (posted 20 August 2005)

KAMITSU MARU Class

Kunitsu Maru (revised 22 August 2018)

OTORI MARU Class

Otori Maru (revised 6 May 2018)

HIKOSHIMA MARU Class

Hikoshima Maru (posted 2 May 2015)
SEIGA MARU Class

Kaika Maru (posted 2 May 2015)

DAICHO MARU Class

Daicho Maru (revised 21 April 2018)
CHOI MARU Class

Choi Maru (revised 21 April 2018)

KIBI MARU Class

Meisho Maru (posted 4 July 2015)

NAGOYA MARU Class

Nagoya Maru (revised 13 March 2010)

KIRI MARU No. 8 Class

Kiri Maru No. 8(posted 4 July 2015)
Shinko Maru No. 1 Go(revised 22 August 2018)



SHOSEI MARU Class

Shosei Maru (revised 23 September 2018)

KYUSHU MARU Class

Kyushu Maru (posted 1 September 2015)
YAYOI MARU Class

Yayoi Maru (posted 1 September 2015)

KATSUYAMA MARU Class

Matsuyama Maru (posted 1 September 2015)

SHOWA MARU Class

Shoho Maru (posted 2 June 2020)


Captured Vessels in Japanese Service as Auxiliary Transports
(Ex-Countries link to specifications summaries)

Ex-American Vessels

Paran Maru (ex-Palawan)
(revised 24 September 2020)
Hokuhi Maru (ex-Cetus)
(posted 2 October 2015)
Anan Maru (ex-Anakan)
(revised 21 April 2018)

Ex-British Vessels

Nichirin Maru (ex-Mata Hari)
(posted 2 November 2015)
Hoki Maru (ex-Hauraki)
(revised 30 April 2016)
Kembu Maru (ex-Empire Blossom)
(posted 2 November 2015)
Keishu Maru (ex-Henry Keswick)
(posted 2 December 2015)
Risui Maru (ex-Lipis)
(posted 2 December 2015)
Kasumi Maru (ex-Kampar)
(posted 2 December 2015)
Dowa Maru (ex-Tung Wo)
(revised 1 July 2016)


Ex-Norwegian Vessels

Manryu Maru (ex-Bordvik)
(posted 3 January 2016)
Ex-Dutch Vessels

Chihaya Maru (ex-Tjisaroea)
(revised 2 November 2018)
Suiten Maru (ex-Schouten)
(posted 3 January 2016)
Kita Maru (ex-Gemma)
(posted 2 February 2016)




Chartered Civilian Vessels in Japanese Service as Auxiliary Transports

YAMATO MARU (ex-GIUSEPPE VERDI) Class

Yamato Maru
(posted 1 August 2014)

Bibliography of Sources

About the Authors

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. Robert Hackett is a military historian and researcher. Retired from the United States Air Force and later from the aerospace industry, he resides on the coast of Florida.

Mr. Peter Cundall is a maritime historian and researcher who specializes in merchant ships. He resides in Australia and works for a towage company.

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