The 12th (Overseas Defence) Battalion was created in November 1939, formed mainly from ex-servicemen around the age of 35–50 and with the duty of garrison duties overseas, in the rear areas guarding important areas and line of communications. In March 1940, the battalion was sent overseas to France, fulfilling its job of guarding the rear echelons, until ordered to evacuate, with the rest of the BEF, and was evacuated from Brest and St. Malo on 16/17 June 1940, without a single casualty. When the battalion returned to the United Kingdom, it followed the usual pattern that consumed the British Army after Dunkirk, mainly guarding against an invasion, which it continued to do so until March 1942, when the 12th Battalion, its services judged to be over, was disbanded. (Other sources say that the battalion was converted into the 189th Field Regiment RA in February 1942. In the following year, it was assigned to the 38th (Reserve) Division, where it remained until it was disbanded in December 1944.)