When Turkey entered the First World War, Newcombe was sent out to Egypt as assistant to Gilbert Clayton, who was head of both the Military and Political Intelligence Services there.
Newcombe served at Gallipoli from September 1915 until December 1915, and was awarded the D.S.O.: "For conspicuous gallantry and devotion to duty near Anzac, Gallipoli Peninsula, on 29 October 1915.