The Battle of Lewes was one of two main battles of the conflict known as the Second Barons' War. It took place at Lewes in Sussex, on May 14, 1264. It marked the high point of the career of Simon de Montfort, 6th Earl of Leicester and made him the "uncrowned King of England".
The battle occurred because of the vacillation of King Henry III, who was refusing to honour the terms of the Provisions of Oxford, an agreement he had signed with his Barons, led by Montfort, in 1258. The King was encamped at St. Pancras Priory with a force of infantry, but his son, Prince Edward (later King Edward I) commanded the cavalry, at Lewes Castle a mile to the north. A night march enabled Montfort's forces to surprise Prince Edward and take the high ground of the Sussex Downs, overlooking the town of Lewes, in preparation for battle. They wore white crosses as their distinguishing emblem.
The royalist army, perhaps as much as twice the size of Montfort's, was led by Edward on the right and the King's brother Richard of Cornwall on the left, while the King himself commanded the central battalion. Having led his men out from the castle to meet the enemy, Edward gained early success, but unwisely pursued a retreating force to the north, thus sacrificing the chance of overall victory. Meanwhile, Montfort defeated the remainder of the Royal army led by the King and Cornwall. All three Royals were eventually captured, and by imprisoning the King, Montfort became the de facto ruler of England.