The regiment mobilised the Royal Hamilton Light Infantry, CASF for active service on 1 September 1939. It was redesignated as the 1st Battalion, the Royal Hamilton Light Infantry, CASF on 7 November 1940. It embarked for Britain on 22 July 1940. The battalion took part in Operation Jubilee on 19 August 1942. (General Denis Whitaker, who fought as a captain with the RHLI at Dieppe, in a 1989 interview stated, “The defeat cleared out all the dead weight. It was the best thing that ever happed to the regiment.”)