Three days after Germany invaded Poland on 1 September 1939, Britain and France declared war. At the time a large majority of Australia's population was of direct British descendants (After all Australia is a British nation)and opposed the German expansion; thus supporting Britain. After the British Government declared war, Prime Minister Menzies announced that ‘Australia was also at war’.
The Australian forces had a difficult decision to make: Defend Australian soil from a possible threat (from Japan), or to support the British forces in Europe. After Japan announced its neutrality and Britain reassured that its naval base in Singapore would stop any Japanese forces advancing; Australia almost completely committed all its forces to supporting the British.
A force and supply system was put into place by Prime Minister Menzies to help prepare the nation for war. The Royal Australian Navy was placed under the control of the British; the Army began recruiting and training men; the nation was preparing its self for war.