53rd (Welsh) Infantry Division included 158th Infantry Brigade, 159th Infantry Brigade, and 160th Infantry Brigade. The first to arrive in Northern Ireland was 158th Infantry Brigade in October 1939. By May 1940, the rest of the Division was also based in Ulster. The increase in troops saw Northern Ireland District divided into 4 areas.
Belfast, Co. Antrim served as Headquarters of 53rd Infantry Division. 158th Infantry Brigade was in the Eastern Area with its base in Lisburn, Co. Antrim. 159th Infantry Brigade was in the Northern Area with its base in Derry/Londonderry. 160th Infantry Brigade was in the Southern Area with its base in Portadown, Co. Armagh.
From June 1941, 53rd (Welsh) Infantry Division and 5th Infantry Division in Northern Ireland came under command of III Corps. 53rd (Welsh) Infantry Division returned to Great Britain in November 1941.