The Brigade traces its historic title back to the First World War when the original 107th Infantry Brigade fought with distinction, alongside its sister formations of 108th Infantry Brigade and 109th Infantry Brigade, as the senior component of 36th Division. In September 1914 it was raised the 1st Brigade of that Division, but on 2 November 1914 it was renumbered 107. The 36th Division itself had been formed in September 1914 as part of the New Armies raised by Kitchener. It consisted of the old Ulster Volunteer Force, which had originally been raised to resist the imposition of Home Rule. Casualties throughout the War meant that many of the original battalions were to be amalgamated or disbanded as hostilities continued. In early 1918, on re-organisation, 107 Brigade consisted of the 1st and 2nd and the 15th Battalions of the Royal Irish Rifles. In March 1918 the 36th Division, in the St Quentin Sector, was part of the Fifth Army and it was upon this Army that the main weight of the German Spring Offensive fell. The retreat which followed ended on 29 March and the Ulster Division moved north to the Ypres Salient. It thereafter took part in the successful offensive operations, which culminated in the cessation of hostilities in November 1918. The 36th Division was demobilised between January and June 1919, having suffered 32,186 casualties during the war.
The second 107 Brigade was to be a Territorial Army formation. The Territorial Army throughout the United Kingdom was reconstituted in 1947 and, for the first time, there was a full scale TA organisation of all Arms in Ulster. Authority was given by the War Office for the formation on 1 January 1947 of 107 Independent Infantry Brigade. Also at this time, Territorial infantry battalions of the three Regular infantry regiments of Northern Ireland were being formed, in addition to the various supporting Arms and Services.
In July 1965 it became known that the reorganisation of the Territorial Army into the Territorial and Army Volunteer Reserve would entail the disbandment of 107 Brigade on 31 March 1967. This was part of the complete reorganisation, announced in the 1966 Defence White Paper, which abolished the former regimental and divisional structure of the Territorial Army. A cell within Headquarters Northern Ireland then oversaw the administration of the Territorial Army in Northern Ireland until the decision was taken that 107 Brigade would again enter the British Army's Order of Battle and this took place on 2 November 1988. It was formed as an administrative headquarters to coordinate the TA units in Northern Ireland. It only became a deployable formation in the 1990s. The Brigade merged on 15 December 2006 into the 39 Infantry Brigade, which was itself replaced by the new regional brigade headquarters, 38 Brigade, on 1 August 2007.
