August 1914 : headquarters and “B” Squadron in Bridgend; “A” Squadron at Swansea; “C” at Cardiff; “D” at Pontypridd. Under command of the South Wales Mounted Brigade. Moved to Hereford on mobilisation, then to Thetford where Brigade came under orders of 1st Mounted Division.
November 1915 : dismounted.
March 1916 : moved to Egypt and formed 4th Dismounted Brigade with the Welsh Border Mounted Brigade.
2 February 1917 : merged with 1/1st Pembroke Yeomanry to form the 24th (Pembroke & Glamorgan Yeomanry) Bn, the Welsh Regiment and came under orders of 231st Brigade in 74th (Yeomanry ) Division. Moved to France in May 1918.
Formed in September 1914 as a Second-Line unit and came under command of 2/1st South Wales Mounted Brigade in January 1915.
September 1915 : Brigade came under orders of 1st Mounted Division.
Brigade redesignated 4th Mounted Brigade in April 1916.
November 1916 : merged with 2/1st Pembroke Yeomanry to form the 2nd (Pembroke & Glamorgan Yeomanry) Cyclist Bn, in 1st Cyclist Brigade.
March 1917 : resumed identity, still in same Brigade.
Formed as a Third-Line training unit in 1915.
Remained in United Kingdom until disbanded in early 1917.