YUSOSEN!

Stories and Battle Histories of the IJN's Oilers and Tanker Fleet

19 August 2017

By Bob Hackett and Peter Cundall

Discussion & Questions


(7,300-ton tanker SAN PEDRO MARU by Ueda Kihachiro)


Oil was a key factor in the Empire of Japan's decision to go to war with America. After Japan occupied southern French Indochina in the summer of 1941, the United States, Great Britain and the Netherlands East Indies placed an embargo on all petroleum products into Japan.

Just before their attack on Pearl Harbor, Japan had only 49 merchant tankers of about 587,000 tons and the IJN had but nine slow fleet oilers. Despite its prewar stockpiling of two years of petroleum products, Japan had to rely on imports from its conquered South Asia territories for survival.

Like all navies, oil was the lifeblood of the IJN. As a result, the IJN requisitioned 77 merchant ships from their owners for conversion to auxiliary oilers (Yusosen). In late 1942, due to shortage of tankers necessary to meet war time demand for oil and gasoline, some cargo ships and ore carriers were converted to temporary tankers during their construction. Twenty existing passenger-cargo ships were converted to emergency tankers called Ohkyu Yusosen.

During the war the Japanese employment of merchants ships was divided into three main administrative categories:
A = requisitioned and operated by the Japanese Army
B = requisitioned and operated by the Japanese Navy with civilian crew (captain often being Navy Reserve)
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.)

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 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 199 fleet and coastal tankers - 75 Navy auxiliaries, 18 Navy fleet oilers, 98 civilian merchant tankers in and 8 captured vessel in Japanese service.

Two of the Navy fleet oilers also served in the seaplane tender role and four were designed as aviation gasoline tankers to resupply carriers underway at sea. The latter Yusosen were officially termed Kihatsuyu Umpankan. Two tankers were converted to escort carriers for the IJA while still on the ways. One of these also would have served as a tanker. Neither became operational.

Some ex-foreign vessels served as tankers, but documenation of their Japanese service for most is either sparse or non-existant.


Special Feature 


Tabular Records of Movement (TROMs):
Auxiliary Tankers and Fleet Oilers
(Classes link to specifications summaries)


TOA MARU Class

Toa Maru(revised 8/4/2017)

Kyokuto Maru (revised 7/8/2017)

ITSUKUSHIMA MARU Class

Itsukushima Maru (revised 6/30/2017)

Genyo Maru (revised 6/25/2017)
Nichiei Maru (revised 7/14/2017)
Toei Maru (revised 8/4/2017)
Kokuyo Maru (revised 6/30/2017)
Kenyo Maru (revised 6/30/2017)

FUJISAN MARU Class

Fujisan Maru(revised 6/25/2017)

TATEKAWA MARU Class

Tatekawa Maru (revised 8/4/2017)

Nippon Maru (revised 7/14/2017)
Toho Maru (revised 8/11/2017)

SHINKOKU MARU Class

Shinkoku Maru (revised 8/4/2017)

HOYO MARU Class

Hoyo Maru (revised 6/25/2017)

Kaijo Maru No. 2 Go (revised 6/30/2017)

AKATSUKI MARU Class

Akatsuki Maru (revised 9/5/2015)

Akebono Maru (revised 6/25/2017)
TEIYO MARU Class

Teiyo Maru (revised 8/4/2017)

SAN RAMON MARU Class

San Ramon Maru (revised 7/30/2017)

San Clemente Maru (revised 7/23/2017)

SAN PEDRO MARU Class

San Pedro Maru (revised 12/24/2016)

San Luis Maru (revised 7/30/2017)
San Diego Maru (revised 7/23/2017)

OGURA MARU No. 2 Class

Ogura Maru No. 2 (revised 7/23/2017)

OGURA MARU No. 3 Class

Ogura Maru No. 3 (revised 7/23/2017)

NISSHO MARU Class

Nissho Maru (revised 6/18/2016)

KYOKUYO MARU Class

Kyokuyo Maru (revised 8/9/2014)

TOEN MARU Class

Toen Maru (revised 8/11/2017)

NISSHIN MARU Class

Nisshin Maru (revised 7/14/2017)

TONAN MARU No. 2 Class

Tonan Maru No. 2 (revised 8/11/2017)

Tonan Maru No. 3 (revised 8/11/2017)
HISHI MARU No. 2 Class

Hishi Maru No. 2 (revised 10/17/2016)

MOJI MARU Class

Moji Maru (posted 7/5/2009)

KYOEI MARU Class

Kyoei Maru (revised 6/12/2016)

KYOEI MARU
No. 2 Class

Kyoei Maru No. 2 (revised 7/8/2017)

Kyoei Maru No. 3 (revised 12/28/2014)

SHOYO MARU Class

Shoyo Maru (revised 8/19/2017)

KINREI MARU Class

Kinrei Maru (revised 3/11/2014)

JUKO MARU Class

Juko Maru (revised 6/29/2013)

KIYO MARU Class

Kiyo Maru (revised 12/28/2014)

HISHI MARU Class

Hishi Maru (revised 10/17/2016)

KORYU MARU Class

Koryu Maru (revised 4/6/2014)

TACHIBANA MARU Class

Manju Maru (revised 3/15/2014)

KUROSHIO MARU Class

Kuroshio Maru (revised 11/1/2016)

STANDARD TANKER 1TL Class

Azusa Maru (revised 10/17/2016)

Seiyo Maru (revised 7/30/2017)
Miri Maru (revised 7/8/2017)
Kyuei Maru (revised 7/8/2017)
Ryoei Maru (revised 7/23/2017)
Nampo Maru (revised 7/8/2017)
Nippo Maru (revised 11/6/2016)
Ominesan Maru (revised 2/19/2012)
Okikawa Maru(revised 7/14/2017)
Amatsu Maru (revised 1/29/2012)
Shimane Maru (posted 10/30/2010)
Kyokuho Maru (revised 2/1/2016)


STANDARD TANKER 1TM Class

Yuho Maru (revised 7/17/2016)

Tarakan Maru(posted 8/29/2009)
Manei Maru (revised 6/12/2016)
Ryuei Maru (revised 9/5/2015)
Shimpo Maru (revised 3/2/2012)
Asanagi Maru (revised 12/1/2014)
Asashio Maru (revised 12/1/2014)
Bokuei Maru (revised 1/29/2012)
Eiho Maru (revised 5/29/2016)
Eiyo Maru No. 2(revised 6/14/2013)
STANDARD TANKER 2TE Class

Murotsu Maru (revised 7/14/2017)

1B Tanker Conversion

Shoyu Maru (posted 10/4/2015)

Peacetime 1K Tanker Conversion

Yamasachi Maru (revised 8/19/2017)

Taketsu Maru (revised 8/19/2017)
Nittetsu Maru(posted 1/3/2016)
Seinan Maru (posted 9/10/2011)
Tainan Maru (posted 5/2/2016)
Tennan Maru (posted 7/3/2016)
Peacetime 1D Tanker Conversion

Nichinan Maru (posted 2/2/2016)

Kotoku Maru (posted 4/2/2016)

Nichiyoku Maru (posted 6/3/2016)

Nikkaku Maru (posted 8/6/2016)

Tokuwa Maru (posted 4/2/2017)

Peacetime 1C Tanker Conversion

Unkai Maru No. 5 (posted 9/3/2016)

Unkai Maru No. 12 (posted 5/2/2017)

Shoei Maru (posted 6/2/2017)

Nittatsu Maru (posted 7/3/2017)

Kanatsu Maru (posted 8/2/2017)



Naval Fleet Oilers
(Classes link to specifications summaries)

SHIRETOKO Class

Shiretoko (revised 10/30/2016)

Notoro (revised 7/14/2017)
Iro (revised 6/30/2017)
Erimo(revised 7/3/2016)
Tsurumi (revised 8/11/2017)
Shiriya (revised 7/3/2016)
Sata (revised 7/1/2017)
Ondo (revised 6/25/2016)
Hayatomo (revised 6/25/2017)
Naruto (revised 7/8/2017)

KAMOI Class

Kamoi (revised 7/30/2017)

HAYASUI Class

Hayasui (posted 1/9/2010)

KAZAHAYA Class

Kazahaya (revised 5/28/2011)

SUNOSAKI Class

Sunosaki (revised 3/1/2017)

Takasaki (revised 7/9/2016)

ASHIZURI Class

Ashizuri (revised 6/25/2017)

Shioya (revised 2/1/2017)


HARIO Class

Hario (revised 6/26/2010))



Civilian Merchant Tankers in Japanese National Service
(Classes link to specifications summaries)

OTOWASAN MARU Class

Omurosan Maru (revised 7/14/2017)


EIYO MARU Class

Eiyo Maru (revised 5/31/2013)


CHIYODA MARU Class

Chiyoda Maru (revised 7/30/2017)

Chihaya Maru (revised 7/30/2017)

STANDARD TANKER 1TL Class

Hashidate Maru (posted 12/3/2010)
Isshin Maru (posted 1/8/2011)
Takane Maru (revised 7/9/2016)
Kyokuei Maru (posted 4/16/2011)


STANDARD TANKER 1TM Class

Jambi Maru(revised 3/30/2014)

Marifu Maru (revised 12/28/2014)

STANDARD TANKER 2AT Class

Daimei Maru (revised 9/10/2011)

Ebara Maru (posted 9/10/2011)
Tatsuyo Maru (posted 9/17/2011)
Daishu Maru (revised 10/29/2011)
Asokawa Maru (posted 10/29/2011)
Kenjo Maru (posted 11/5/2011)
Osakasan Maru (posted 11/12/2011)
Akikawa Maru (posted 11/19/2011)
Otsusan Maru (posted 11/26/2011)
Eiwa Maru (posted 12/2/2011)
Tamon Maru No. 15 (posted 12/10/2011)
Yamazawa Maru (posted 12/17/2011)
Daigyo Maru (posted 12/24/2011)
Daietsu Maru (posted 2/4/2012)
Ojikasan Maru (posted 3/3/2012)
Encho Maru (posted 5/5/2012)
Enkei Maru (posted 6/2/2012)
Daito Maru (posted 7/7/2012)
Enryaku Maru (posted 8/4/2012)
Engen Maru (posted 9/1/2012)
Awagawa Maru (posted 10/6/2012)
Yamazono Maru (posted 11/3/2012)
Oesan Maru (posted 12/1/2012)
Eisho Maru (posted 1/5/2013)
Yamanami Maru (posted 2/2/2013)
Einin Maru (posted 2/2/2013)
Dainan Maru (posted 3/2/2013)
STANDARD TANKER 2TL Class

Jinei Maru (revised 12/25/2014)

Seria Maru (posted 7/1/2013)
Mitsushima Maru (posted 8/1/2013)
Tenei Maru (posted 8/1/2013)
Arita Maru (posted 9/1/2013)
Tojo Maru(revised 8/11/2017)
Fujisan Maru(revised 2/1/2016)
Kaiho Maru(posted 12/1/2013)
Munakata Maru(posted 1/1/2014)
Akashi Maru (posted 2/1/2014)
Amato Maru (posted 8/2/2015)
Akane Maru (posted 4/1/2014)
Matsushima Maru (posted 5/1/2014)
Tatekawa Maru No. 2 (posted 7/1/2014)
Yamashio Maru (posted 5/1/2014)
Chikuma Maru (posted 8/1/2014)
Kyokuun Maru (revised 10/1/2014)
Yuyo Maru (posted 11/1/2014)
Toho Maru (posted 2/1/2016)
Daiho Maru (posted 2/1/2016)
Taiei Maru (posted 4/1/2017)
STANDARD TANKER 2TM Class

Ayagiri Maru (posted 4/1/2017)

Ayanami Maru (posted 4/1/2017)
Ayayuki Maru (posted 4/1/2017)
Ayazono Maru (posted 4/1/2017)
Baiei Maru (posted 4/1/2017)
Fuei Maru
Gyoshin Maru
Hikoshima Maru
Hosho Maru
Koshin Maru
Oei Maru
Ritsuei Maru
Ryuei Maru
Ryusho Maru
Sanyo Maru
Shimotsu Maru
Shokai Maru
Shoei Maru
Soei Maru

Military & Civilian Auxiliary Passenger-Cargo Ships
Converted to Emergency Tankers (OHKYU YUSOSEN)
(Classes link to specifications summaries)


GOYO MARU Class

Goyo Maru (revised 6/25/2017)

AZUMA MARU Class

Azuma Maru (revised 10/17/2016)

Arima Maru (posted 12/5/2009)
KUMAGAWA MARU Class

Kumagawa Maru (revised 6/30/2017)

Kozui Maru (posted 9/24/2011)

TERUKAWA MARU Class

Terukawa Maru (revised 8/4/2017)

LYONS MARU Class

Taketoyo Maru (revised 4/1/2017)

Matsumoto Maru (revised 7/30/2017)
Tatsuno Maru (revised 9/1/2016)

KIRISHIMA MARU Class

Kirishima Maru (revised 6/30/2017)

HAKUBASAN MARU Class

Hakubasan Maru (revised 11/1/2013)

SEIAN MARU Class

Seian Maru (revised 7/3/2013)

Hokuan Maru (posted 10/8/2011)

KONSAN MARU Class

Konsan Maru (posted 6/2/2012)

Ronsan Maru (posted 7/7/2012)

NASUSAN MARU Class

Nasusan Maru (posted 8/4/2012)

KOSHIN MARU Class

Koshin Maru (posted 9/1/2012)

SHINSHU MARU Class

Shinshu Maru (posted 6/1/2016)

SHUNTEN MARU Class

Shunten Maru (posted 12/1/2014)

ASUKA MARU Class

Atago Maru revised 2/1/2016)


Captured and Foreign Vessels in Japanese Service as Tankers
(Ex-Countries link to specifications summaries)

Ex-American Vessel

Sanraku Maru (ex-USS Sara
Thompson AO-8)
(Posted 5/5/2012)

Ex-British Vessels

Choran Maru (ex-Lake
Champlain)
(revised 8/2/2015)
Enoshima Maru (ex-RFA Ebonol)(revised 8/2/2015)

Ex-Dutch Vessels

Ose (ex-Genota) (revised 3/24/2014)
Kyoko Maru (ex-Semiramis)(revised 8/9/2015)
Hosei Maru (ex-Poseidon)(revised 10/1/2016)
Yosei Maru (ex-Josefina)(revised 2/1/2016)
Anjo Maru(ex-Angelina)(posted 10/1/2013)
Tango Maru (ex-Talang Akar)(posted 4/6/2013)

Bibliography of Sources

About the Authors

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

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.