Australia entered the Second World War on 3 September 1939 . At the time of the declaration of war against Germany the Australian military was small and unready for war . Recruiting for a Second Australian Imperial Force ( 2nd AIF ) began in mid @-@ September . While it was no rush of volunteers like the First World War , a high proportion of Australian men of military age had enlisted by mid @-@ 1940 . Four infantry divisions were formed during 1939 and 1940 , three of which were dispatched to the Middle East . The RAAF 's resources were initially mainly devoted to training airmen for service with the Commonwealth air forces through the Empire Air Training Scheme ( EATS ) , through which almost 28 @,@ 000 Australians were trained during the war .