Army (軍, gun) was a term in the Imperial Japanese Army was used in different ways to designate a variety of large military formations that corresponded to the army group, field army, and corps in the militaries of Western nations.

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The General Army (総軍, Sō-gun) was the highest level in the organizational structure of the Imperial Japanese Army. It corresponded to the army group in western military terminology. Intended to be self-sufficient for indefinite periods, the general armies were commanded by either a field marshal or a full general.

The initial General Army was the Japanese Manchurian Army, formed from 1904 to 1905 during the Russo-Japanese War as a temporary command structure to coordinate the efforts of several Japanese armies in the campaign against Imperial Russia.

In terms of a permanent standing organization, the Japanese Army created the Kantōgun, usually known in English as the Kwantung Army, to manage its overseas deployment in the Kwantung Territory and Manchukuo from 1906.

Subsequent general armies were created in response to the needs of the Second Sino-Japanese War and World War II, in which increased overseas deployment called for an organizational structure that could respond quickly and autonomously from the Imperial Japanese Army General Staff in Tokyo. As a result, Japanese forces were re-organized into three separate overseas operational commands: (Manchuria, China and Southeast Asia), with the Japanese home islands forming a fourth.

Towards the end of World War II, the home island command (i.e. the General Defense Command) was restructured geographically into the First General Army in the east, Second General Army in the west, and the Air General Army in charge of military aviation.

With the official Japanese surrender in September 1945, all of the general armies were dissolved, except for the First General Army, which continued to exist until November 30, 1945, as the 1st Demobilization Headquarters.

Area Armies (方面軍, Hōmen-gun) in Japanese military terminology were equivalent to field armies in western militaries. Area Armies were normally commanded by a general or lieutenant general. There is much confusion between the similarly numbered Area Armies and Armies in historical records, as many writers often did not make a clear distinction when describing the units involved.

The Japanese Army (軍, gun) corresponded to an army corps in American or British military terminology. It was usually commanded by a lieutenant general.

• • First Army – China
  • Second Army – China
  • Third Army – Manchukuo
  • Fourth Army – Manchukuo
  • Fifth Army – Manchukuo
  • Sixth Army – Manchukuo
  • Tenth Army – China
  • Eleventh Army – China
  • Twelfth Army – China
  • Thirteenth Army – China
  • Fourteenth Army – Philippines
  • Fifteenth Army – Burma
  • Sixteenth Army – Java
  • Seventeenth Army – Solomon Islands
  • Eighteenth Army – New Guinea
  • Nineteenth Army – eastern Netherlands East Indies
  • Twentieth Army – China
  • Twenty-First Army – China
  • Twenty-Second Army – China
  • Twenty-Third Army – China
  • Twenty-Fifth Army – Malaya, Singapore, Sumatra
  • Twenty-Seventh Army – Chishima Islands
  • Twenty-Eighth Army – Burma
  • Twenty-Ninth Army – British Malaya
  • Thirtieth Army – Manchukuo
  • Thirty-First Army – Truk
  • Thirty-Second Army – Okinawa
  • Thirty-Third Army – Burma
  • Thirty-Fourth Army – Manchukuo
  • Thirty-Fifth Army – Philippines
  • Thirty-Sixth Army – Japanese home islands
  • Thirty-Seventh Army – Borneo
  • Thirty-Eighth Army -Indochina
  • Thirty-Ninth Army -Thailand
  • Fortieth Army – Japanese home islands
  • Forty-First Army – Philippines
  • Forty-Third Army – China
  • Forty-Fourth Army – Manchukuo
  • Fiftieth Army – Japanese home islands
  • Fifty-First Army – Japanese home islands
  • Fifty-Second Army – Japanese home islands
  • Fifty-Third Army – Japanese home islands
  • Fifty-Fourth Army – Japanese home islands
  • Fifty-Fifth Army – Japanese home islands
  • Fifty-Sixth Army – Japanese home islands
  • Fifty-Seventh Army – Japanese home islands
  • Fifty-Eighth Army – Korea
  • Fifty-Ninth Army – Japanese home islands
  • China Garrison Army – China
  • Mongolia Garrison Army- Inner Mongolia
  • Army of Tokyo Bay
  • Tokyo defense Army
• Imperial Japanese Army Air Force
  • First Air Army – HQ Tokyo, basing in the Kanto Plain covering the Japanese home islands, Taiwan, Korea and Karafuto.
  • Second Air Army – HQ Xinjing, covering Manchukuo
  • Third Air Army – HQ Singapore, covering Southeast Asia
  • Fourth Air Army – HQ Rabaul, covering the Solomon Islands and New Guinea
  • Fifth Air Army – HQ Nanjing, covering Japanese-occupied portions of southern and eastern China.
  • Sixth Air Army – HQ Kyūshū covering Taiwan and Okinawa

• Organizations of Imperial Japanese Army & Navy Archived 2012-04-26 at the Wayback Machine