On 1 May 1914, Legge was appointed Chief of the General Staff, with the rank of full colonel, but he did not sail for home until July 1914. By the time Legge reached Adelaide, war had broken out. With Bridges occupied in organising the Australian Imperial Force (AIF), Legge took over the organisation of the Australian Naval and Military Expeditionary Force for service in New Guinea. When Bridges departed for overseas, Legge took over responsibility for the training of AIF reinforcements.