The first indication of rationalisation of The Ulster Defence Regiment occurred when the 1st and the 9th Battalion The Ulster Defence Regiment merged to form the 1st/9th (County Antrim) Battalion The Ulster Defence Regiment. The in-place location chosen for the Battalion Headquarters was the former 9 UDR Battalion Headquarters in the town of Antrim in County Antrim. Ballymena had been the location of 1 UDR’s headquarters and, as both battalions had been located in County Antrim, it was appropriate that the new battalion title carried the county name.

The amalgamation was marked by a parade held at St Patrick’s Barracks, Ballymena.