Following Britain's declaration of war on Germany on 4 August 1914, Australia and the other members of the British Empire became automatically involved, with Prime Minister Joseph Cook stating on 5 August 1914 that "..when the Empire is at war, so also is Australia."
Within days, plans for an Australian expeditionary force were completed by Brigadier General William Throsby Bridges and his staff officer, Major Cyril Brudenell Bingham White.