YUSOSEN!

YUSOSEN!

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

11 October 2024

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 Un´eikai (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

Borneo Oil Fields and Refineries Under Imperial Japanese Navy Control

Surabaya, Java Naval Base, Oil Fields and Refineries Under Imperial Japanese Navy Control

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

TOA MARU Class
Toa Maru(revised 30 July 2024)

Kyokuto Maru (revised 7/21/2018)

ITSUKUSHIMA MARU Class
Itsukushima Maru (revised 30 July 2024)
Genyo Maru (revised 30 July 2024)
Nichiei Maru (revised 30 July 2024)
Toei Maru (revised 30 July 2024)
Kokuyo Maru (revised 7/10/2020) Kenyo Maru (revised 30 July 2024)
FUJISAN MARU Class
Fujisan Maru(revised 30 July 2024)
TATEKAWA MARU Class
Tatekawa Maru (revised 30 July 2024)

Nippon Maru (revised 7/21/2018)
Toho Maru (revised 30 July 2024)

SHINKOKU MARU Class
Shinkoku Maru (revised 30 July 2024)
HOYO MARU Class
Hoyo Maru (revised 1/14/2018)

Kaijo Maru No. 2 Go (revised 30 July 2024)

AKATSUKI MARU Class
Akatsuki Maru (revised 30 July 2024)
Akebono Maru (revised 30 July 2024)
TEIYO MARU Class
Teiyo Maru (revised 10/7/2018)

SAN RAMON MARU Class
San Ramon Maru (revised 9/14/2020)

San Clemente Maru (revised 9/14/2020)

SAN PEDRO MARU Class
San Pedro Maru (revised 2/12/2021)

San Luis Maru (revised 7/27/2018)
San Diego Maru (revised 7/20/2020)

OGURA MARU No. 2 Class
Ogura Maru No. 2 (revised 7/27/2018)
OGURA MARU No. 3 Class
Ogura Maru No. 3 (revised 10/1/2018)
NISSHO MARU Class
Nissho Maru (revised 8/27/2022)

KYOKUYO MARU Class
Kyokuyo Maru (revised 2/12/2021)
TOEN MARU Class
Toen Maru (revised 2/12/2021)

NISSHIN MARU Class
Nisshin Maru (revised 3/23/2021)

TONAN MARU No. 2 Class
Tonan Maru No. 2 (revised 30 July 2024)

Tonan Maru No. 3 (revised 8/11/2017)
HISHI MARU No. 2 Class
Hishi Maru No. 2 (revised 8/27/2022)
MOJI MARU Class
Moji Maru (revised 9/6/2020)

KYOEI MARU Class
Kyoei Maru (revised 3/23/2021)
KYOEI MARU
No. 2 Class
Kyoei Maru No. 2 (revised 11/9/2020)

Kyoei Maru No. 3 (revised 9/6/2020)

SHOYO MARU Class
Shoyo Maru (revised 11/9/2020)
KINREI MARU Class
Kinrei Maru (revised 11/9/2020)

JUKO MARU Class
Juko Maru (revised 9/6/2020)

KIYO MARU Class
Kiyo Maru (revised 11/9/2020)
HISHI MARU Class
Hishi Maru (revised 11/9/2020)
KORYU MARU Class
Koryu Maru (revised 9/6/2020)
TACHIBANA MARU Class
Manju Maru (revised 9/6/2020)

KUROSHIO MARU Class
Kuroshio Maru (revised 9/6/2020)
STANDARD TANKER 1TL Class
Azusa Maru (revised 2/12/2021)

Seiyo Maru (revised 10/19/2020)
Miri Maru (revised 1/27/2018)
Kyuei Maru (revised 8/27/2022)
Ryoei Maru (revised 8/27/2022)
Nampo Maru (revised 11/13/2018)
Nippo Maru (revised 11/13/2018)
Ominesan Maru (revised 9/14/2020)
Okikawa Maru(revised 11/13/2018)
Amatsu Maru (revised 9/14/2020)
Shimane Maru (posted 10/30/2010)
Kyokuho Maru (revised 3/19/2023)

STANDARD TANKER 1TM Class
Yuho Maru (revised 7/10/2020)

Tarakan Maru(posted 9/24/2020)
Manei Maru (revised 11/12/2018)
Ryuei Maru (revised 10/5/2020)
Shimpo Maru (revised 9/24/2020)
Asanagi Maru (revised 12/1/2014)
Asashio Maru (revised 11/12/2018)
Bokuei Maru (revised 9/14/2020)
Eiho Maru (revised 11/12/2018)
Eiyo Maru No. 2(revised 9/14/2020)
STANDARD TANKER 2TE Class
Murotsu Maru (revised 10/5/2020)

1B Tanker Conversion
Shoyu Maru (revised 7/27/2018)
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 (revised 2/2/2018)

Tokuwa Maru (posted 4/2/2017)
Peacetime 1C Tanker Conversion
Unkai Maru No. 5 (posted 9/3/2016)
Unkai Maru No. 12 (posted 2/23/2018)
Shoei Maru (posted 6/2/2017)
Nittatsu Maru (posted 7/3/2017)
Kanatsu Maru (posted 1/21/2018)
Hozan Maru (posted 11/3/2019)

Naval Fleet Oilers (Classes link to specifications summaries)

SHIRETOKO Class
Shiretoko (revised 3/19/2023)

Notoro (revised 11/13/2018)
Iro (revised 10/11/2024) Erimo(revised 7/6/2018) Tsurumi (revised 11/9/2020) Shiriya (revised 2/23/2018) Sata (revised 6/18/2024) Ondo (revised 3/19/2023) Hayatomo (revised 3/19/2023) Naruto (revised 7/21/2018)
KAMOI Class
Kamoi (revised 9/14/2020)
HAYASUI Class
Hayasui (posted 1/9/2010)
KAZAHAYA Class
Kazahaya (revised 5/28/2011)
SUNOSAKI Class
Sunosaki (revised 3/1/2017)

Takasaki (revised 11/14/2018)

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 30 July 2024)

EIYO MARU Class
Eiyo Maru (revised 11/12/2018)

CHIYODA MARU Class
Chiyoda Maru (revised 10/1/2018)

Chihaya Maru (revised 11/12/2018)

STANDARD TANKER 1TL Class

Hashidate Maru (revised 3/23/2021)
Isshin Maru (revised 3/23/2021)
Takane Maru (revised 2/16/2018) Kyokuei Maru (revised 3/29/2023)

STANDARD TANKER 1TM Class
Jambi Maru(revised 7/13/2018)

Marifu Maru (revised 7/21/2018)

STANDARD TANKER 2AT Class
Daimei Maru (revised 6/5/2023)

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 1/21/2018)
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 30 July 2024)
AZUMA MARU Class
Azuma Maru (revised 30 July 2024)

Arima Maru (revised 30 July 2024)
KUMAGAWA MARU Class
Kumagawa Maru (revised 11/12/2018)

Kozui Maru (posted 9/24/2011)

TERUKAWA MARU Class
Terukawa Maru (revised 30 July 2024)

LYONS MARU Class
Taketoyo Maru (revised 4/1/2017)

Matsumoto Maru (revised 30 July 2024)
Tatsuno Maru (revised 9/1/2016)
KIRISHIMA MARU Class
Kirishima Maru (revised 30 July 2024)

HAKUBASAN MARU Class
Hakubasan Maru (revised 11/1/2013)

SEIAN MARU Class
Seian Maru (revised 7/3/2013)

Hokuan Maru (revised 6/11/2024)

KONSAN MARU Class
Konsan Maru (posted 6/2/2012)

Ronsan Maru (posted 7/7/2012)
NAGISAN MARU Class
Nasusan Maru (posted 8/4/2012)

KOSHIN MARU Class
Koshin Maru (revised 7/13/2018)

SHINSHU MARU Class
Shinshu Maru (posted 6/1/2016)
SHUNTEN MARU Class
Shunten Maru (revised 30 July 2024)
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 1/14/2018)
Enoshima Maru (ex-RFA Ebonol)(revised 7/6/2018)
Ex-Dutch Vessels

Ose (ex-Genota) (revised 3/24/2014)
Kyoko Maru (ex-Semiramis)(revised 7/13/2018)
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.

TOA MARU Class Toa Maru(revised 30 July 2024) Kyokuto Maru (revised 7/21/2018)	ITSUKUSHIMA MARU Class Itsukushima Maru (revised 30 July 2024) Genyo Maru (revised 30 July 2024) Nichiei Maru (revised 30 July 2024) Toei Maru (revised 30 July 2024) Kokuyo Maru (revised 7/10/2020) Kenyo Maru (revised 30 July 2024)	FUJISAN MARU Class Fujisan Maru(revised 30 July 2024)	TATEKAWA MARU Class Tatekawa Maru (revised 30 July 2024) Nippon Maru (revised 7/21/2018) Toho Maru (revised 30 July 2024)	SHINKOKU MARU Class Shinkoku Maru (revised 30 July 2024)	HOYO MARU Class Hoyo Maru (revised 1/14/2018) Kaijo Maru No. 2 Go (revised 30 July 2024)	AKATSUKI MARU Class Akatsuki Maru (revised 30 July 2024) Akebono Maru (revised 30 July 2024)	TEIYO MARU Class Teiyo Maru (revised 10/7/2018)
SAN RAMON MARU Class San Ramon Maru (revised 9/14/2020) San Clemente Maru (revised 9/14/2020)	SAN PEDRO MARU Class San Pedro Maru (revised 2/12/2021) San Luis Maru (revised 7/27/2018) San Diego Maru (revised 7/20/2020)	OGURA MARU No. 2 Class Ogura Maru No. 2 (revised 7/27/2018)	OGURA MARU No. 3 Class Ogura Maru No. 3 (revised 10/1/2018)	NISSHO MARU Class Nissho Maru (revised 8/27/2022)	KYOKUYO MARU Class Kyokuyo Maru (revised 2/12/2021)	TOEN MARU Class Toen Maru (revised 2/12/2021)	NISSHIN MARU Class Nisshin Maru (revised 3/23/2021)
TONAN MARU No. 2 Class Tonan Maru No. 2 (revised 30 July 2024) Tonan Maru No. 3 (revised 8/11/2017)	HISHI MARU No. 2 Class Hishi Maru No. 2 (revised 8/27/2022)	MOJI MARU Class Moji Maru (revised 9/6/2020)	KYOEI MARU Class Kyoei Maru (revised 3/23/2021)	KYOEI MARU No. 2 Class Kyoei Maru No. 2 (revised 11/9/2020) Kyoei Maru No. 3 (revised 9/6/2020)	SHOYO MARU Class Shoyo Maru (revised 11/9/2020)	KINREI MARU Class Kinrei Maru (revised 11/9/2020)	JUKO MARU Class Juko Maru (revised 9/6/2020)
KIYO MARU Class Kiyo Maru (revised 11/9/2020)	HISHI MARU Class Hishi Maru (revised 11/9/2020)	KORYU MARU Class Koryu Maru (revised 9/6/2020)	TACHIBANA MARU Class Manju Maru (revised 9/6/2020)	KUROSHIO MARU Class Kuroshio Maru (revised 9/6/2020)	STANDARD TANKER 1TL Class Azusa Maru (revised 2/12/2021) Seiyo Maru (revised 10/19/2020) Miri Maru (revised 1/27/2018) Kyuei Maru (revised 8/27/2022) Ryoei Maru (revised 8/27/2022) Nampo Maru (revised 11/13/2018) Nippo Maru (revised 11/13/2018) Ominesan Maru (revised 9/14/2020) Okikawa Maru(revised 11/13/2018) Amatsu Maru (revised 9/14/2020) Shimane Maru (posted 10/30/2010) Kyokuho Maru (revised 3/19/2023)	STANDARD TANKER 1TM Class Yuho Maru (revised 7/10/2020) Tarakan Maru(posted 9/24/2020) Manei Maru (revised 11/12/2018) Ryuei Maru (revised 10/5/2020) Shimpo Maru (revised 9/24/2020) Asanagi Maru (revised 12/1/2014) Asashio Maru (revised 11/12/2018) Bokuei Maru (revised 9/14/2020) Eiho Maru (revised 11/12/2018) Eiyo Maru No. 2(revised 9/14/2020)	STANDARD TANKER 2TE Class Murotsu Maru (revised 10/5/2020)
1B Tanker Conversion Shoyu Maru (revised 7/27/2018)	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 (revised 2/2/2018) Tokuwa Maru (posted 4/2/2017)	Peacetime 1C Tanker Conversion Unkai Maru No. 5 (posted 9/3/2016) Unkai Maru No. 12 (posted 2/23/2018) Shoei Maru (posted 6/2/2017) Nittatsu Maru (posted 7/3/2017) Kanatsu Maru (posted 1/21/2018) Hozan Maru (posted 11/3/2019)