The regiment was formed on the creation of the Territorial Force in April 1908 and placed under orders of the South Wales Mounted Brigade. It was headquartered at Tenby with the squadrons being headquartered as follows:
- A Squadron: Tenby (with drill stations at Pembroke, St Florence, Manorbier, Kilgetty and Templeton)
- B Squadron: Haverfordwest (Clarbeston Road, Newgale and Fishguard)
- C Squadron: Carmarthen (Whitland, Llanelly, Llandilo, Llangadock, Pantglas and Llandovery)
- D Squadron: Lampeter (Aberystwyth, Tregaron, Llandyssil and Llanbyther).
1/1st Pembroke (Castlemartin) Yeomanry
- August 1914 : moved to Hereford after mobilising, but by the end of the month had moved to Thetford (Norfolk) where brigade came under orders of 1st Mounted Division. The brigade then moved to the Aylsham area and the regiment went to nearby Haveringham and Heydon.
- November 1915 : dismounted.
- March 1916 : moved to Egypt. On arrival the brigade merged with Welsh Border Mounted Brigade and formed the 4th Dismounted Brigade.
- 2 February 1917 : merged with 1/1st Glamorgan Yeomanry to form the 24th (Pembroke & Glamorgan Yeomanry) Battalion, the Welsh Regiment and came under orders of 231st Brigade in 74th (Yeomanry ) Division.
- Moved to France in May 1918.
2/1st Pembroke Yeomanry
- Formed as a Second-Line regiment in September 1914. Moved to Carmarthen in early 1915, coming under orders of 2/1st South Wales Mounted Brigade. Moved during the year to Llandilo, Dorchester and by September was at Yoxford. Brigade came under orders of 1st Mounted Division.
- June 1916 : converted to a cyclist unit under orders of 2nd Cyclist Brigade in 1st Cyclist Division.
- November 1916 : regiment merged with 2/1st Glamorgan Yeomanry to form 2nd (Pembroke & Glamorgan) Yeomanry Cyclist Regiment, under 1st Cyclist Brigade.
- March 1917 : by now at Aldeburgh, resumed identity but remained in brigade. Moved in July to Benacre and by end of year moved to Lowestoft where it then remained.
3/1st Pembroke Yeomanry
- Formed as a Third-Line training unit at Carmarthen around May 1915 and then moved to Brecon.
- Summer 1916: dismounted and attached to 3rd-Line groups of the Welsh Division at Oswestry.
- February 1917: disbanded, with some men going to 2/1st Pembroke Yeomanry and others to 4th Reserve Battalion of the Welsh Regiment at Milford Haven.
In the 1917 renumbering of the Territorials, the Pembroke Yeomanry issued numbers from the block 290001-295000. Corps of Hussars.
The regimental collection is at
Scolton Manor Museum
Tel: 01437 731328