 At the start of the war , Australia 's military forces were focused upon the militia and what Regular forces existed were mostly serving in the artillery or engineers and were assigned in most part to the task of coastal defence . Due to the provisions of the Defence Act 1903 , which precluded sending conscripts overseas , upon the outbreak of war it was realised that a totally separate , all volunteer force would need to be raised . This force was known as the Australian Imperial Force ( AIF ) . 
