Chichester-Clark was an officer in the 1st Battalion, Irish Guards, part of 24th Guards Brigade attached to British 1st Infantry Division, and participated briefly in the Anzio landings. He was injured on 23 February 1944 by an 88m shell as he and his Platoon Sergeant took their first look at the ground in the 'gullies' to the west of the Anzio-Albano road. His company were all but wiped out, and he spent most of his war in hospital recovering from injuries, the effects of which stayed with him throughout his life. Following the war, his military career took him from the dull duties of the post-war occupation of Germany, to Canada as aide-de-camp to Harold Alexander, 1st Earl Alexander of Tunis, then Governor General of Canada. The popularity and competence of his senior officer made this uneventful two-year period of Chichester-Clark's life the most remarkable element of his pre-parliamentary career. On returning from Canada, Chichester-Clark continued in the Army for several years, refusing promotion to seniority before retiring a major in 1960.