The was an

army An army, ground force or land force is an armed force that fights primarily on land. In the broadest sense, it is the land-based military branch, service branch or armed service of a nation or country. It may also include aviation assets by ...

of the

Imperial Japanese Army The Imperial Japanese Army (IJA; , ''Dai-Nippon Teikoku Rikugun'', "Army of the Greater Japanese Empire") was the principal ground force of the Empire of Japan from 1871 to 1945. It played a central role in Japan’s rapid modernization during th ...

during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

History

The Japanese 31st Army was formed on February 18, 1944 under the

Imperial General Headquarters The was part of the Supreme War Council (Japan), Supreme War Council and was established in 1893 to coordinate efforts between the Imperial Japanese Army and Imperial Japanese Navy during wartime. In terms of function, it was approximately equi ...

as a garrison force to contest landings by Allied forces in the Japanese

South Seas Mandate The South Seas Mandate, officially the Mandate for the German Possessions in the Pacific Ocean Lying North of the Equator, was a League of Nations mandate in the " South Seas" given to the Empire of Japan by the League of Nations following W ...

island-by-island, and to inflict such losses in a

war of attrition The War of Attrition (; ) involved fighting between Israel and Egypt, Jordan, the Palestine Liberation Organisation (PLO) and their allies from 1967 to 1970. Following the 1967 Six-Day War, no serious diplomatic efforts were made to resolve t ...

that it would deter an American invasion of the

Japanese home islands The is an archipelago of 14,125 islands that form the country of Japan. It extends over from the Sea of Okhotsk in the northeast to the East China and Philippine seas in the southwest along the Pacific coast of the Eurasian continent, and cons ...

. The South Seas Mandate was divided into three sections (

Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an Territories of the United States, unincorporated territory and Commonwealth (U.S. insular area), commonwealth of the United States consistin ...

, southern Mariana Islands, and Truk). The 80,000 man Japanese 31st Army was initially headquartered on Truk. After

Operation Hailstone Operation Hailstone was a large-scale United States Navy air and surface attack on Truk Lagoon on 17–18 February 1944, conducted as part of the American offensive drive against the Imperial Japanese Navy in the Pacific Ocean theatre of Worl ...

, the Japanese garrison on Truk was isolated as American forces continued their advance towards Japan by invading other Pacific islands. Cut off, the Japanese forces on Truk and other central Pacific islands ran low on food and faced starvation before Japan surrendered in August 1945. (Stewart, 1986) The garrisons in the Marianas were largely annihilated at the

Battle of Saipan The Battle of Saipan was an amphibious assault launched by the United States against the Empire of Japan during the Pacific War, Pacific campaign of World War II between 15 June and 9 July 1944. The initial invasion triggered the Battle of the ...

and Battle of Guam.

Structure

;Thirty-First Army *Southern Marianas Force ** 29th Infantry Division **48th Independent Infantry Brigade *Northern Marianas Force ** 43rd Infantry Division **47th Independent Infantry Brigade *Truk Garrison Force ** 52nd Infantry Division **50th Independent Infantry Brigade **51st Independent Infantry Brigade **52nd Independent Infantry Brigade

List of commanders

Commanding officer

Chief of Staff

References

* * * * * * *{{cite book , last = Jones , first = Don , authorlink = , year = 1986 , chapter = , title = Oba, The Last Samurai , publisher = Presidio Press , location = , isbn = 0-89141-245-X 31 Military units and formations established in 1944 Military units and formations disestablished in 1945