[4] During the Second World War the role of the District was enhanced from internal security to that of combatting any threat of invasion from the Republic of Ireland.

[3] In June 1940, VI Corps was formed to control the British forces based in Northern Ireland.

Northern Ireland District was made responsible for local defence, and under certain conditions would control at least one division based there.

However, BTNI became responsible for the overall defence of the territory and if needed would control forces assigned to Plan W, to counter a German invasion of the Republic of Ireland.

The British Army's presence reached a peak of four divisions and generally maintained this strength (through the use of American troops after 1942) for most of the war.

The tanks had been transported to Northern Ireland on board the amphibious landing ship HMS Fearless, and were operated with their turrets traversed to the rear and main guns covered by tarpaulins.

[12] On 6 August 2007 HQ Northern Ireland and 38 (Irish) Brigade combined to create a single transitional headquarters with a two star General Officer Commanding.