 He fought in the First World War, receiving the Military Cross in 1915.He was promoted to a brevet-major in 1917, mentioned in despatches seven times during the course of the war, and was awarded the Distinguished Service Order in 1918 and the French Croix de Guerre in 1920.Floyer-Acland attended the Staff College, Camberley in 1921 and was breveted to lieutenant colonel in 1927.