The Normans had begun to make incursions into Wales, pushing westward from their bases in recently occupied England from the late 1060s onward, their advance marked by the construction of castles and the creation of regional lordships.

The task of subduing the region of Glamorgan had been given to the earls of Gloucester in 1093; efforts continued throughout the twelfth and early thirteenth centuries, accompanied by extensive fighting between the Anglo-Norman lords and local Welsh rulers.

The powerful de Clare family had acquired the earldom in 1217 and continued to attempt to conquer the whole of the Glamorgan region.

Gilbert de Clare was born at Christchurch, Hampshire, the son of Richard de Clare, Earl of Hertford and Gloucester, and of Maud de Lacy, Countess of Lincoln, daughter of John de Lacy and Margaret de Quincy.

Gilbert, also known as "Red Gilbert" because of the color of his hair, had inherited his father's estates in 1262, and from 1263had assumed the titles, including Lord of Glamorgan.

Being under age at his father's death, he had been made a ward of Humphrey de Bohun, Second Earl of Hereford.

Opposing him in Glamorgan is the native Welsh prince Llywelyn the Last, who had taken advantage of the chaos of the civil war in England between Henry III and rebel barons during the 1260s to expand his power across the region.