The United States came to the defence of Australia with reticence. The US pre-war plans for the Pacific enshrined in War Plan Orange had not included Australia as a significant base or partner in the event of a war against Japan. Plans for the US advance across the Pacific had also primarily focused on the central and northern part of the ocean.

Yet this had not meant that Australia had been completely discarded. The move by US military officials from national to coalition war planning after the start of the war in Europe in 1939 meant that Australia appeared on a number of occasions in the US ‘Rainbow’ series of war plans. In some of these plans the Australian mainland was mentioned, but only as a stopover port for the US fleet on its way to possible operations in Southeast Asia. Of greater importance to the United States were the Australian mandated territories in the South Pacific.

During the 1920s and 1930s these territories, especially Rabaul on the eastern tip of New Britain, had often been suggested by US planning groups as a possible avenue of advance against the Japanese in the event of war, but after detailed discussions this option ‘had always been rejected’. The strategic location of these territories, adjacent to the Japanese possessions in the Central Pacific, meant that their importance to both the Japanese and the Americans was self-evident. As such an agreement between the US and Australian governments was reached in October 1941 that allowed for the US military to help secure the Australian territories. But by the time US forces were ready to deploy to Rabaul and the surrounding islands they had already fallen to the Japanese.