At the outbreak of civil war in AD 1642, Charles I enjoyed the support of the majority of the Welsh people whereas Parliament was supported in the English-dominated parts of the country. Carmarthenshire was Royalist for most of the war, but its neighbour, Pembrokeshire, was for Parliament under its leaders John Poyer, mayor of Pembroke, and Rowland Laugharne.

The Royalist Association of Carmarthenshire, commanded by Richard Vaughan, 2nd Earl of Carbery, marched on Pembrokeshire in 1643, capturing Tenby and Haverfordwest. These victories were reversed a year later when Rowland Laugharne and his forces reached Carmarthen. After his defeat, Carbery resigned. His replacement, Sir Charles Gerard, succeeded in driving the Parliamentarians back into Pembrokeshire, only to be defeated again by Laugharne. Attacks and counter-attacks by both armies continued until 1645, when Charles I was decisively defeated at the battle of Naseby. Carmarthen then surrendered to Laugharne’s forces.

However, in 1648, Laugharne and his forces defected to the Royalists. Oliver Cromwell led the Parliamentary army west, stopping at Carmarthen on his way to besiege Pembroke Castle. Carmarthen Castle was largely demolished, probably on Cromwell’s orders. When Charles II was restored to the throne in 1660, there was general rejoicing and the King’s health was drunk in the town.