Details from The Midland Regiment were called out on service on 26 August 1939 and then placed on active service on 1 September 1939, for local protection duties under the designation The Midland Regiment (Northumberland and Durham), CASF (Details). These details were disbanded on 31 December 1940. The regiment then mobilized The Midland Regiment (Northumberland and Durham), CASF, for active service on 24 May 1940 and was redesignated the 1st Battalion, The Midland Regiment (Northumberland and Durham), CASF, on 7 November 1940. The 1st Battalion served in Canada in a home defence role as part of the Prince Rupert Defences, 8th Canadian Division. The Battalion embarked for Great Britain on 10 January 1945, where it was disbanded on 18 January 1945 to provide reinforcements to the Canadian Army in the field.