bigpigeon.us webpage WWII Japan > Order Of Battle > OOB - Armies & Corps, © 2024 by Robert A. Christiansen, updated by RAC 12 Apr 2024. 
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The major US Army Ground Forces involved in the Pacific Area in the War with Japan
See also WWII Japan > Order of Battle > OOB - Divisions.​
The United States Army fielded three field armies in the War with Japan.
  • The Sixth Army conducted combat operations in Western New Guinea (I and XI Corps), in Leyte (X and  XXIV Corps), and in Luzon (I, XIV, and later XI Corps). It then was released from combat to prepare for the invasion of Kyushu in the Japanese Home Islands.
  • The Eighth Army relieved the Sixth Army in Western New Guinea and later in Leyte. It then conducted combat operations in the Southern Philippines (X Corps) and subsequently relieved the Sixth Army in Luzon.
  • The Tenth Army (XXIV Corps and III Marine Amphibious Corps) conducted combat operations in Okinawa and nearby islands in the Ryukyu Island chain.
Sixth Army, New Guinea and Bismarck Archipelago phase, when it existed with a parallel organization known as Alamo Force:
  • ​1 Jun 1943 - Sixth Army activated at Camp Columbia, Brisbane, Australia.
  • 16 Jun 1944 - HQ Sixth Army & HQ Alamo Force opened at Hollegang, near Hollandia, Dutch New Guinea.
  • 21–23 Sep 1944 - Operation details for Sixth Army Leyte-Samar operation, including X Corps and XXIV Corps, issued
  • 25 Sep 1944 - Alamo Force discontinued and remaining missions transferred to Sixth Army.
  • 28 Sep–12 Oct 1944 - control of Sixth Army rear area units, including I Corps and XI Corps, passed to Eighth Army.
Sixth Army, Philippines phase:
  • 20 Oct 1944 - Assault elements of Sixth Army's X and XXIV Corps land in the Tacloban-Dulag area of eastern Leyte.
  • Dec 1944 - Sixth Army elements landed in the San Jose area of Mindoro Island, 150 miles south of Manila.
  • 26 Dec 1944 - Control of Sixth Army units and operations on Leyte-Samar, including X Corps and XXIV Corps, passed to Eighth Army.
  • 9 Jan 1945 - Assault elements of Sixth Army's I and XIV Corps land on Lingayen Gulf 150 miles north of Manila.
  • 29 Jan 1945 - Elements of XI Corps land in Subic Bay area of western Luzon.
  • 1 Jul 1945 - Sixth Army relieved by Eighth Army on Luzon.
Eighth Army:​
  • 7 Sep 1944 - Sixth Army HQ arrived Hollandia area, Dutch New Guinea from the continental US.
  • 28 Sep–12 Oct 1944 - progressively assumed control of Sixth Army units in Australia, New Guinea, and Bismarck Archipelago.
  • 13 Oct–15 Nov 1944 - relinquished combat responsibility in Aitape, New Guinea and in New Britain to First Australian Army.
  • 20 Nov 1944 - Eighth Army HQ opened in Leyte.
  • 26 Dec 1944 - Eighth Army assumed control of Sixth Army units and operations on Leyte and Samar.
  • 1 Jan 1945 - Eighth Army assumed control of Sixth Army units and operations on Mindoro.
  • 1 Jul 1945 - Eighth Army relieved Sixth Army on Luzon and assumed control of XIV Corps. 
  • 15 Aug 1945 - Offensive action on Luzon ceased; Eighth Army directed to establish airhead in the Tokyo area and then occupy northern Honshu & Hokkaido in the Japanese Home Islands.
​Tenth Army:
  • 2 Sep 1944 - Tenth Army headquarters established at Schofield Barracks, Oahu, Hawaii.
  • 11 Oct 1944–5 Jan 1945 - Tenth Army engaged in planning and preparation for Ryukyu operation.
  • XXIV Corps assigned to Tenth Army.
  • 19 Mar 1945 - Tenth Army command post established on USS Eldorado off Leyte.
  • 26 Mar 1945 - Tenth Army's 77th Division landed on Kerama Retto south of Okinawa.
  • 1 Apr 1945 - Tenth Army's XXIV Corps (7th and 96th Divisions) and III Amphibious Corps (1st and 6th Marine Divisions) landed south and north of Hagushi on west coast of Okinawa.
  • 9 Apr 1945 - control of 27th Division passed from Tenth Army to XXIV Corps; 27th Division elements begin landing on 10 Apr.
  • 18 Apr 1945 - Tenth Army command post established near Koza, Okinawa.
  • ​2 Jul 1945 - Ryukyus Campaign officially declared ended.
The United States Army eventually had six corps in the Pacific Area, five of which engaged in combat.
I Corps:
  • 1942 - activated in Australia.
  • 2 Oct 1942 - I Corps assigned to US Army Forces in Australia.
  • 16 Feb 1943 - I Corps assigned to Sixth Army.
  • 22 Apr 1944 - I Corps landed at Hollandia, Dutch New Guinea.
  • 15 Jun 1944 - I Corps assumed command of Hurricane Task Force on Biak Island, Dutch New Guinea.
  • 29 Jun 1944 - I Corps relieved of command of Hurricane Task Force on Biak and returned to Hollandia area.
  • 2 Oct 1944 - I Corps assigned to Eighth Army.
  • 20 Nov 1944 - I Corps relieved of responsibility for defense of Hollandia area and assigned to Sixth Army.
  • 9 Jan 1945 - I Corps landed in Lingayen Gulf, Luzon.
  • 30 Jun 1945 - I Corps relieved of responsibility for combat missions assigned to it.
IX Corps: (Never saw combat.)
  • 17 Oct 1944: IX Corps arrived Oahu, Hawaii. 
  • 10 Jul 1945: IX Corps arrived Leyte and assigned to Sixth Army.
  • 11 Jul 1945: IX Corps began preparing plans for Operation Olympic, invasion of Kyushu, Japan.
  • 15 Aug 1945: IX Corps assigned to Eighth Army.
​X Corps:
  • 31 Jul 1944 - X Corps arrived in theater Oro Bay, New Guinea; assigned to Sixth Army.
  • 7 Aug 1944 - X Corps moved to Finschhaven, New Guinea and began planning for Leyte-Samar operation.
  • 9 Aug–8 Oct 1944 - X Corps engaged in planning Leyte Operation.
  • 20 Oct 1944 - X Corps landed on east coast of Leyte under control of Sixth Army.
  • 26 Dec 1944 - X Corps reassigned from Sixth Army to Eighth Army.
  • 25 Feb–12 Apr 1945 - X Corps engaged in planning Victor V operation on Mindanao.
  • 17 Apr 1945 - X Corps troops landed at Parang, Mindanao.
  • 18 Apr 1945 - X Corps HQ opened at Parang, Mindanao.
  • 30 Jun 1945 - Mindanao Campaign officially terminated.
  • 15 Aug 1945 - Offensive operations ceased and X Corps reassigned from Eighth Army to Sixth Army.
XI Corps:
  • 22 Apr 1944 - XI Corps arrived in theater Finschhaven, New Guinea and assigned to Sixth Army.
  • 27 Jun 1944 - XI Corps assumed command of Persecution Task Force at Aitape, New Guinea from 32nd Infantry Division.
  • 25 Aug 1944 - command of Persecution Task Force returned to 32nd Infantry Division.
  • 26 Aug–8 Sep 1944 - XI Corps engaged in planning Morotai operation.
  • 15 Sep 1944 - XI Corps elements landed on Morotai, Dutch Indies.
  • 12 Oct 1944 - XI Corps reassigned from Sixth Army to Eighth Army.
  • 14 Nov 1944 - XI Corps arrived Leyte.
  • 15 Nov 1944–15 Jan 1945 - XI Corps engaged in planning Subic Bay operation on Luzon.
  • 26 Dec 1944 - XI Corps reassigned from Sixth Army to Eighth Army.
  • 29 Jan 1945 - XI Corps elements landed near Subic Bay on Luzon.
  • 30 Jan 1945 - XI Corps reassigned from Eighth Army to Sixth Army.
  • 1 Jul 1945 - XI Corps relieved of responsibility for all combat operations on Luzon.
  • 2 Jul-15 Aug 1945 - XI Corps engaged in planning Operation Olympic, invasion of Kyusyu Island.
  • 15 Aug 1945 - XI Corps reassigned from Sixth Army to Eighth Army.
XIV Corps:
  • 2 Jan 1943 - using Americal Division personnel, provisional skeletal XIV Corps headquarters established on Guadalcanal and assigned to US Army Forces in South Pacific Area (Halsey).
  • 9 Feb 1943 - Guadalcanal Campaign ends.
  • 28 February 1943 - main XIV Corps headquarters units arrived on Guadalcanal.
  • 30 Jun 1943 - US military begins New Georgia campaign.
  • 15 Jul 1943 - XIV Corps assumes control of New Georgia Occupation Force from the 43rd Infantry Division.
  • 7/15 Oct 1943 - New Georgia campaign ends.
  • 15 December 1943 - XIV Corps relieves I Marine Amphibious Corps on Bougainville.
  • 13 Jun 1944 - XIV Corps assigned to US Army Forces Far East (MacArthur).
  • 20 Nov 1944 - XIV Corps assigned to Sixth Army.
  • 9 Jan 1945 - XIV Corps landed in Lingayen Gulf, Luzon.
  • 1 Jul 1945 - XIV corps reassigned from Sixth Army to Eighth Army.
XXIV Corps:
  • 8 Apr 1944 - XXIV Corps headquarters activated on Oahu; assigned to US Army Forces in the Central Pacific.
  • 3 Oct 1944 - XXIV Corps headquarters arrived at Manus Island, Admiralty Islands.
  • 14 Oct 1944 - XXIV Corps and subsidiary units departed Manus in convoy to participate in Sixth Army landing on Leyte Island, Philippines. 
  • 18 Oct 1944 - XXIV Corps attached to Southwest Pacific Area.
  • 19 Oct 1944 - XXIV Corps attached to Sixth Army.
  • 20 Oct 1944–10 Feb 1945 - XXIV corps engaged in Leyte Island campaign. Major attached units during all or part of campaign included 7th, 77th, and 96th Divisions and 11th Airborne Division.
  • 20 Oct 1944 - XXIV Corps units landed on east coast of Leyte; corps headquarters landed 21 Oct.
  • 26 Dec 1944 - XXIV Corps attachment changed from Sixth Army to Eighth Army.
  • 10 Feb 1945 - XXIV Corps relieved of all tactical responsibility for Leyte and assigned to Tenth Army.
  • 24 Mar 1945 - XXIV Corps and subsidiary units departed Leyte in convoy to participate in Tenth Army's Ryukyu Islands campaign. Major attached units during part or all of campaign included 7th, 27th, 77th, and 96th Divisions and 1st Marine Division.
  • 1 Apr 1945 - 7th and 96th Divisions landed south of Hagushi on west coast of Okinawa; corps headquarters landed 5 Apr.
  • 2 Jul 1945 - Ryukyus Campaign ended.
  • 3 Jul–11 Aug 1945 - XXIV Corps engaged in planning for Operation Olympic, the Sixth Army invasion of Kyushu.
  • 15 Aug 1945 - XXIV Corps assigned to United States Army Forces Pacific and tasked with occupying Korea.
​Sources for Big Pigeon's WWII Japan > Order of Battle > OOB - Armies & Corps webpage: