Tenth U.S. Army / 10th Army

Naval commanders exercised operational control over Army forces throughout the war. The only employment of a field army in POA occurred in the Central Pacific when the Tenth Army took part in the Ryukyus campaign. Activated on 20 June 1944 at Ft. Houston, it passed to the command of Lieutenant General Simon Bolivar Buckner, Jr., who had been in charge of the Alaska Defense Command. Among the major units involved in the Ryukyus operation were the XXIV Corps, released from action in the Philippines on 10 February 1945, and the III Amphibious Corps (Marine). The size of the total force numbered around 183,000 personnel for the assault phases, with approximately 154,000 men in seven combat divisions. The 81st Division was excluded as it remained in New Caledonia.

The Tenth Army differed in several respects from field armies in other theaters, including those employed in Europe and the Mediterranean. First of all, Tenth Army remained under the operational direction of a naval commander throughout its land campaign. Second, unlike the Sixth or Eighth armies, it constituted a joint task force containing Marine (III Amphibious Corps), Navy (Naval Forces, Ryukyus), and Air (Tactical Air Force, Ryukyus, under a Marine major general) elements under its direct command. Third, as a result of this mixture of forces from different services, Buckner organized his staff to include naval and marine officers. More so than any other operation, the Campaign to seize Okinawa in the closing days of World War II represents the greatest joint effort undertaken by the US Military. Tenth Army operations in the Okinawa Campaign of 1945 constitute the only historical example of a joint field army headquarters which included corps size units of both the US Army and the Marine Corps. From its organization to the way it fought, Tenth Army incorporated every element of the service to a degree never before attempted and never since replicated. Although Okinawa was the largest joint operation of the war, it was not the largest planned joint operation. Operation DOWNFALL, the campaign to seize the Japanese islands, was the largest planned. So Okinawa was really a test of how joint operations at the large unit level could be conducted.