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YUSOSEN!

  • ️Sun Jan 14 2018

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

19 February 2025

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 

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)
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)
 		TENZAN MARU Class

Konsan Maru (revised 25 January 2025)

Ronsan Maru (posted 25 January 2025)
 		NAGISAN MARU Class

Nasusan Maru (revised 20 January 2025)

 HORAISAN MARU Class

Koshin Maru

(revised 27 January 2025)
 SHINSHU MARU Class

Shinshu Maru (revised 19 February 2025)

 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)

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.