In the First World War, Boyle was commissioned as a second lieutenant in the Oxfordshire and Buckinghamshire Light Infantry on 14 September 1914.[4] He was promoted to temporary lieutenant on 9 December 1914,[5] temporary captain on 23 July 1915,[6] substantive lieutenant on 14 July 1916[7] and substantive captain on 24 June 1917.[8] He was wounded and relinquished his commission on 8 May 1919 due to ill health.[9]
Boyle married Marion Elisa Hill Wallace, daughter of Major-General Hill Wallace, on 12 February 1918.