In the First World War he served on the Western Front and in the Sinai and Palestine campaign, where he commanded the 10th Cavalry Brigade.

He was commissioned as a second-lieutenant into the 3rd Battalion, Green Howards (Princess of Wales's Own Yorkshire Regiment) on 19 November 1892, part of the militia.

On 3 October 1897 he transferred from the East Yorkshire Regiment, still as a second-lieutenant but with seniority from 7 December 1895 to the Indian Staff Corps after a period of probation.

His elder son Brigadier Percy William Powlett Green died on 23 February 2004.

His younger son Wing Commander Wilfrith Peter Green was killed in action with the Royal Air Force on 1 March 1945.