Japan's entry into the Second World War in December 1941 confirmed the collective strategic and racial fears of several generations of Australians. The Pacific war served also to show up the inability of the British to defend Australia, and the necessity for Australians to defend themselves. Despite two years of war Australia was in no way prepared for the Japanese onslaught when it came, and the legacy of inter-war neglect was paid for by young militiamen, poorly trained and equipped, in New Guinea in 1942. That, in the event, Australia was not invaded and overrun by the Japanese owed nothing to the defence preparations of the preceding twenty years.

Some preparations had been made none the less, for as noted earlier the government was mindful of the Japanese threat when making its initial force contributions to the war in Europe and the Mediterranean. Japanese intentions in the region were increasingly plain from the fall of France onwards, even if one discounted the war waged in China from 1931. German occupation of France and the Netherlands raised questions about the control of their colonial possessions in South-east Asia and the Pacific. The administration of the Netherlands East Indies remained in the allied camp after the fall of the metropolitan government, but the government of French Indo-China became a Vichy one, and acceded to Japanese pressure to stop the traffic of war material through Indo-Chinese ports on its way to China.