The Hastings and Prince Edward Regiment, CASF, mobilized for active service on 1 September 1939 and was redesignated the 1st Battalion, The Hastings and Prince Edward Regiment, CASF, on 7 November 1940. The unit embarked for Great Britain on 22 December 1939, and on 13 June 1940 it went to France as part of the Second British Expeditionary Force, reaching a point beyond Laval before being ordered back to the United Kingdom. It landed in Sicily on 10 July 1943, and in Italy on 3 September 1943, as part of the 1st Infantry Brigade, 1st Canadian Infantry Division. On 10 March 1945, the battalion moved with the I Canadian Corps to northwest Europe, where it fought until the end of the war. The overseas battalion was disbanded on 15 October 1945. On 1 June 1945, a second Battalion of the regiment was mobilized for service in the Pacific theatre of operations as the 2nd Canadian Infantry Battalion (The Hastings and Prince Edward Regiment), CASF. The 2nd Battalion was disbanded on 1 November 1945.