The 139th Battalion (Northumberland), CEF, was authorized on 22 December 1915 and embarked for Great Britain on 27 September 1916 where its personnel were absorbed by the 36th Reserve Battalion, CEF on 6 October 1916 to provide reinforcements to Canadian units in the field.
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.