By the end of 1944, the German "Luftwaffe" was suffering from such shortages of pilots, aircraft and fuel that serious aerial attacks on the United Kingdom could be discounted and the War Office began reorganising surplus AA units in the UK into infantry battalions for duties in the rear areas. Meanwhile, 21st Army Group fighting in North West Europe was suffering a severe manpower shortage, particularly among the infantry. In January 1945, the War Office accelerated the conversion of surplus artillery into infantry units, primarily for line of communication and occupation duties, thereby releasing trained infantry for frontline service. 64th S/L Regiment was selected for conversion on 23 January 1945, and redesignated 639 (Essex Regiment) Infantry Regiment, RA, with five 'batteries' designated A to E.