During the 1930s Germany was expanding its territory. In 1939 it threatened to invade Poland. Britain and France warned that if Germany invaded, they would declare war. Germany did invade on 1 September, and on 3 September Britain and France declared war.
Australia was a British nation. People in Australia were opposed to German expansion, but they were also very closely tied to Britain. When the British Government declared war, Prime Minister Menzies announced that ‘Australia was also at war’.
With the coming of war, Australia had to make a decision: whether to look after home defence (there was a fear that Japan might try and expand its power), or to commit troops to help England. Japan had pledged its neutrality, and England had assured Australia that it was secure from Japan - the British naval base at Singapore would stop any Japanese advance towards Australia. So Australia committed itself to a European War.
Australia was not well-prepared to fight a war, and in this early part of the war Prime Minister Menzies stressed that it was ‘Business As Usual’ while an effective force and supply system were developed. The Royal Australian Navy was put under the control of the British; the Army began recruiting and training men; and RAAF men were promised to help the Royal Air Force.