Map of the South West Pacific Theater
The forerunner of the South West Pacific Area was the short-lived American-British-Dutch-Australian Command (ABDA). In December 1941 and January 1942 ABDA was referred to as the South West Pacific Area. The rapid Japanese advance through the Dutch East Indies effectively divided the ABDA area in two and, in late February 1942, ABDA was dissolved at the recommendation of its commander, Field Marshal Sir Archibald Wavell, who—as Commander-in-Chief in India—retained responsibility for Allied operations in Burma and Sumatra.
Another command, established under emergency conditions when a convoy intended for supply of the Philippines, known as the Pensacola Convoy, was rerouted to Brisbane due to the attack on Pearl Harbor. Brigadier General
Julian F. Barnes was ordered to assume command of all troops in the convoy on 12 December 1941 concurrent with their designation as Task Force—South Pacific, and place himself under the command of MacArthur. The next day, by radiogram, the Chief of Staff of the United States Army, General George C. Marshall, ordered Barnes to assume command as Commander, US Troops in Australia and take charge of all troops and supplies. On 22 December 1941, with the convoy's arrival in Brisbane, the command was designated as United States Forces in Australia (USFIA). It was renamed U.S. Army Forces in Australia (USAFIA) on 5 January 1942. Its mission was to create a base in Australia for the support of the forces still in the Philippines.
The staff, known as the "Remember Pearl Harbor" (RPH) group, selected by the War Department for USAFIA arrived Melbourne 1 February 1942 aboard SS President Coolidge and SS Mariposa in the first large convoy bearing personnel, supplies and munitions intended for transhipment to Java and Philippines as well as Australia. For a brief time, due to the increased isolation of the Philippines and before the fall of Java, UASFIA was withdrawn from MacArthur's command and placed under the ABDA with continued direction to support both Java and the Philippines.
What would replace ADBA was the subject of discussions between the Australian and New Zealand chiefs of staff that were held in Melbourne between 26 February and 1 March 1942. They proposed creating a new theatre of war encompassing Australia and New Zealand, under the command of Wavell's former deputy, Lieutenant General George Brett, who had assumed command of the US Army Forces in Australia (USAFIA) on 25 February.
The President of the United States, Franklin Roosevelt, and the Prime Minister of the United Kingdom, Winston Churchill, discussed the matter of command arrangements in the Pacific in Washington, D.C., on 9 March. Roosevelt proposed that the world would be divided into British and American areas of responsibility, with the United States having responsibility for the Pacific, where there would be an American supreme commander responsible to the Joint Chiefs of Staff. Churchill responded favourably to the proposal, and the governments of Australia and New Zealand were then consulted. They endorsed the idea of an American supreme commander, but wanted to have some input into matters of strategy.
This resulted in the creation of the Pacific War Council, which met for the first time in London on 10 February 1942. Churchill, Clement Attlee (Deputy Prime Minister) and Anthony Eden (Foreign Secretary) represented the United Kingdom, and Earle Page represented Australia, along with representatives from the Netherlands, New Zealand, India and China. Page was replaced as the Australian representative by Stanley Bruce in June 1942. A parallel Pacific War Council was created in Washington, D.C., that first met on 1 April 1942. It was chaired by Roosevelt, with Richard Casey and later Owen Dixon representing Australia, and Prime Minister Mackenzie King representing Canada. The Pacific War Council never became an effective body, and had no influence on strategy, but did allow the Dominions to put their concerns before the President.