 Paton joined the Australian Imperial Force on 16 March 1915 as a lieutenant colonel commanding the 25th Battalion, part of the 7th Infantry Brigade, which embarked for Egypt on 2 June 1915 where it trained until it embarked for Gallipoli on 28 August 1915.Paton took over the 7th Brigade on 15 October 1915 on direct orders from Major General James Gordon Legge.During the evacuation of Anzac, Paton was placed in command of the Rear Party, and at 0410 on 20 December Paton embarked on the last boat to leave Anzac.