The 1st Battalion, Irish Fusiliers (Vancouver Regiment), CASF, mobilized for active service on 1 January 1941. The battalion served in Canada in a home defence role as part of the 18th Infantry Brigade, 6th Canadian Division; and in Jamaica on garrison duty from 18 May 1943 to 6 August 1944. On 10 January 1945 it embarked for Britain, where it was disbanded on 19 January 1945 to provide reinforcements to the Canadian Army in the field. The 3rd Battalion, Irish Fusiliers (Vancouver Regiment), CASF, mobilized for active service on 12 May 1942. This unit served in Canada in a home defence role as part of the 19th Infantry Brigade of Pacific Command. The 3rd Battalion was disbanded on 15 August 1943.