The Battle of Monmouth took place on 25 November 1233, the feast day of St Catherine, between forces loyal to Henry III, King of England, and those of Richard Marshal, Earl of Pembroke and Lord Marshal of England, who had formed an alliance with the Welsh prince Llywelyn ap Iorwerth and his supporter Owain ap Gruffydd, a grandson of Rhys of Deheubarth.

According to the chronicler Roger of Wendover in his Flores Historiarum (Flowers of History), Marshal and his knights then came to Monmouth to reconnoitre the town before besieging it.

He was a nobleman of Flanders who, with his mixed force of Flemings and Poitevins, had been entrusted by King Henry with defending the town.

[1] The battle was depicted in an illustration by 13th-century historian Matthew Paris, which shows Richard Marshal unhorsing Baldwin of Guisnes.

Other sources suggest, on the basis of an order placed in 1234 for thirty oaks from the Forest of Dean to repair the Church of St Thomas the Martyr, located to the south-west of the town, that the adjoining Monnow Bridge would have been the one mentioned in the chronicle of the fighting and which was partly destroyed at that time.