Koseki Umpansen

Histories of the IJN's Ore Carriers

1 November 2017

By Bob Hackett

Discussion & Questions

(Japanese wartime ore carrier by Ueda Kihachiro)

Japan possesses few mining resources. Her wartime military-industrial capacity was dependent on key strategic raw materials imported by sea such as coal, iron, bauxite (aluminum), copper and zinc. A similar dependency existed for imports of crude rubber, ferro-alloys such as manganese, chrome, nickel, cobalt and for non-ferrous metals such as tin, lead, and mercury.

Japan had no domestic source of bauxite ore, but prior to, and during the war, obtained bauxite from Bintang Island (near Singapore), Dutch East Indies, and Manchuria. In 1941, 90 percent of aluminum ingots were produced from bauxite imported from the Dutch East Indies. Hainan Island, China was a source of bauxite, copper, and tin and the Palaus in the Carolines were also a source of bauxite and phosphates.

Before the war, Japan had investments in iron and tin mines and rubber planations in Malaya; and other interests in nickel, sulphur, manganese and coal from Indochina and other Asian locations. Japan imported iron from Korea, Formosa, China, Malaya and the Philippines and other areas. Her steel processes used much scrap iron. Tungsten for Japan’s iron works was provided from Occupied China.

Losses of merchant vessels, raw materials and petroleum greatly weakened Japan. Sixty percent of her merchant fleet’s losses were caused by the American submarine offensive. Allied air warfare further reduced Japan's merchant fleet.

Japan's aircraft production was strongly affected by the lack of raw materials. Reduction of bauxite imports from the Dutch East Indies resulted in a 70 percent drop in aluminum production. Imports of 16 key materials fell from 20 million tons in 1941 to 10 million tons in 1944 and to 2.7 million tons in the first six months of 1945.

To meet wartime demands for strategic raw materials, the Japanese expanded construction of merchant ships built as ore carriers. The YASUKUNI MARU class was the first of these new designs, followed by the SHONAN MARU, KINREI MARU and HOREI MARU classes.

In 1943, Japan adopted the Standard Merchant Type 1K ore carrier design and work began in private yards. Thirty-seven ore carriers were completed during the war, of which six were converted to emergency tankers. Twenty ore carriers were Standard Merchant Type 1Ks.

In addition to its fleet of ore carriers, Japan also constructed bulk carriers to transport cargo including raw materials.

Japanese Ore Carriers:
Tabular Records of Movement (TROMs)

(Classes link to specifications summaries)

Yasukuni Maru Class

Yasukuni Maru (revised 11/1/2011)

Toyokuni Maru (posted 8/19/2011)

Shonan Maru Class

Shonan Maru (posted 8/27/2011)
Honan Maru (posted 9/3/2011)
Seinan Maru (posted 9/10/2011)

Kinrei Maru Class

Kinrei Maru (posted 9/17/2011)
Nikko Maru (posted 9/24/2011)
Ginrei Maru (posted 10/1/2011)
Batopahat Maru (revised 4/1/17)

Horei Maru Class

Horei Maru (revised 10/29/2011)

Gyokurei Maru (posted 10/29/2011)

Standard Merchant Type 1K Class

Akikawa Maru (posted 11/19/2011)

Daikyo Maru (posted 11/19/11)
Daigo Maru (posted 12/2/11)
Daizen Maru (revised 4/1/17)
Daiyoku Maru (posted 4/7/12)
Gyokuyo Maru (posted 5/5/12)
Hida Maru (posted 6/2/12)
Hidaka Maru (posted 7/7/12)
Hikachi Maru (posted 8/4/12)
Hinaga Maru (posted 9/4/12)
Hiyori Maru (posted 10/6/12)
Higane Maru (posted 11/3/12)
Hioki Maru (posted 12/1/12)
Kokka Maru (posted 1/5/13)
Kokko Maru (posted 2/2/13)
Kokusei Maru (posted 3/2/13)
Nichirei Maru (posted 5/4/13)
Nikkyo Maru (posted 6/1/13)
Tatsubato Maru (posted 7/1/13)

Bibliography of Sources

About the Author

Bob 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.

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