4 Brigade South Donegal – 1 Northern Division

This brigade consisted of 5 battalions: 1 Battalion (South Donegal) and the 1, 2 and 3 Battalions, along with the Derry City Independent Battalion.
1 (South Donegal) Battalion: Unit strength on 11 July 1921 was 291 all ranks. After July 1921 this unit merged with the 3 Northern Division. The companies of the 1 (South Donegal) Battalion were located as follows: Ballyshannon, Bundoran, Kinlough, Tullaghan, Cliffoney and Pettigo.
1 Battalion: Unit strength on 11 July 1921 was 602 all ranks and the strength on 1 July 1922 was 687 all ranks. The companies of the 1 Battalion were located as follows: Castlederg, Cloghan, Meenakerrin, Clady, Killygordan, Sion Mills, Gleneely, Ballymongan, Lismulladuff, Castlefinn, Ballybofey and Laughtmorris.
2 Battalion: Unit strength on 11 July 1921 was 430 all ranks and the strength on 1 July 1922 was 526 all ranks. The companies of the 2 Battalion were located as follows: Ballyshannon, Beleek, Mulleck, Ballintra, Donegal, Laghey Bar, Meenadreen and Townaivilly.
3 Battalion: Unit strength on 11 July 1921 was 197 all ranks and the strength on 1 July 1922 was 175 all ranks. The companies of the 3 Battalion were located as follows: Pettigo, Edenery, Lettercran and Tamur.
Derry City Independent Battalion, 4 Brigade, 1 Northern Division: Unit strength on 11 July 1921 was 348 all ranks and the strength on 1 July 1922 was 328 all ranks. All five companies of this battalion were located in Derry City.