 In Australia , the outbreak of World War I was greeted with considerable enthusiasm . Even before Britain declared war on Germany on 4 August 1914 , the nation pledged its support alongside other states of the British Empire and almost immediately began preparations to send forces overseas to participate in the conflict . The first campaign that Australians were involved in was in German New Guinea after a hastily raised force known as the Australian Naval and Military Expeditionary Force was dispatched from Australia to seize German possessions in the Pacific in September 1914 . At the same time another expeditionary force , initially consisting of 20 @,@ 000 men and known as the First Australian Imperial Force ( AIF ) , was raised for service overseas . 
