At the outbreak of the First World War, Butterworth, together with several of his friends, including Geoffrey Toye and R. O. Morris, joined the British Army as a private in the Duke of Cornwall's Light Infantry, but he soon accepted a commission as a subaltern (2nd Lieutenant) in the 13th Battalion Durham Light Infantry, and he was later temporarily promoted to lieutenant. He was known as G. S. Kaye-Butterworth in the Army. Butterworth's letters are full of admiration for the ordinary miners of County Durham who served in his platoon. As part of 23rd Division, the 13th DLI was sent into action to capture the western approaches of the village of Contalmaison on The Somme. Butterworth and his men succeeded in capturing a series of trenches near Pozières on 16–17 July 1916, the traces of which can still be found within a small wood. Butterworth was slightly wounded in the action. For his action Temporary Lt. George Butterworth, aged 31, was awarded the Military Cross, gazetted 25 August 1916, though he did not live to receive it.