Harlech Castle in Gwynedd surrendered to Parliamentarian forces on 13 March 1647 after a long blockade. It was the last Royalist-held fortress on the British mainland from the First Civil War. Its fall marked the completion of Parliament's military conquest of Wales.

Harlech's endurance entered Welsh and Royalist memory as a story of loyalty under siege. The castle's dramatic landscape encouraged later antiquarian and poetic treatments of civil conflict embedded in national place.