The 2nd Battalion returned to the United Kingdom and, on 7 December 1941 (the day the United States entered the war), transferred to the 37th Independent Infantry Brigade (redesignated 7th Infantry Brigade the day after). On 1 March 1944 the battalion was transferred to the newly created 56th Independent Infantry Brigade, alongside which were the 2nd Battalion, Essex Regiment and 2nd Battalion, Gloucestershire Regiment and trained for the invasion of Normandy. The battalion had the distinction of being the only Welsh battalion to take part in the Normandy landings on 6 June 1944, landing at Gold Beach under command of 50th (Northumbrian) Infantry Division and fought in the Battle of Normandy, under command of 7th Armoured Division for a few days in June 1944, before reverting to the 50th Division. In August 1944 it was briefly under command of the 59th (Staffordshire) Infantry Division and fought in the Battle of the Falaise Gap. On 20 August the brigade joined the 49th (West Riding) Infantry Division, replacing the disbanded 70th Brigade. With the division, the battalion fought in the operations to clear the Channel coast, where they captured Le Havre in Operation Astonia. Afterwards the battalion enjoyed a short rest and, on 22 September, moved to join the rest of the 21st Army Group fighting in Belgium. In October, shortly after the failure of Operation Market Garden, the division was sent to garrison the "Island", as the area of land between Arnhem and Nijmegen was known, where it remained throughout the northern winter of 1944/45. The last major action for the battalion was in April 1945 when, with the rest of the division, they fought in the Second Battle of Arnhem. The battalion ended its war in Germany, and remained there, as part of the occupation forces, until 1948 when it returned home. During the campaign in North-western Europe the battalion had suffered over 100% casualties.