Australia 's role in the Pacific War declined from 1944 . The increasing size of the US forces in the Pacific rendered the Australian military superfluous and labour shortages forced the Government to reduce the size of the armed forces to boost war production . Nevertheless , the Government wanted the Australian military to remain active , and agreed to MacArthur 's proposals that it be used in relatively unimportant campaigns . In late 1944 , Australian troops and RAAF squadrons replaced US garrisons in eastern New Guinea , New Britain , and Bougainville , and launched offensives aimed at destroying or containing the remaining Japanese forces there . In May 1945 , I Corps , the Australian First Tactical Air Force and USAAF and USN units began the Borneo Campaign , which continued until the end of the war . These campaigns contributed little to Japan 's defeat and remain controversial .