Between March 1941 and March 1942, 5th Infantry Division as a whole operated in Ulster under British Troops in Northern Ireland (B.T.N.I.) providing defence.
On 10th April 1941, lorries and equipment of the British Army's 5th Infantry Division disembarked from a ferry arriving at Larne Harbour, Larne, Co. Antrim.
In 1941, 5th Reconnaissance Battalion, divisional troops of 5th Infantry Division operated in Northern Ireland as part of a defence against potential invasion.
15th Infantry Brigade was part of 5th Infantry Division of the British Army during its time in Northern Ireland defending against the threat of Nazi invasion.