On May 14, 1264, at the Battle of Lewes during the Second Barons' War, Simon de Montfort the younger, Earl of Leicester, defeated and captured English King Henry III. A short excerpt from the text:
"Historical Background
In 1216 England was engulfed in the First Barons War where senior Anglo-Norman magnates were fighting to overthrow King John for his repudiation of Magna Carta. The accession of the young Henry III, coupled with a policy of reconciliation by the new regime and victories at a number of key battles, had seen that war end. However, medieval society relied upon a strong King who could strike a balance between exercising his authority and managing his Barons. Henry III lacked this skill and by the late 1250s the country was once again on the cusp of civil war as the Baronial faction was angered by his autocratic rule and promotion of favourites.
Matters came to a head in 1258 when Henry III was forced by his Barons to agree the Provisions of Oxford; a treaty which required the King to surrender key powers, particularly on taxation and inheritance, to a council headed by Simon de Montfort, Earl of Leicester. In a parallel with his father and Magna Carta, Henry III sought and was granted Papal annulment of the Provisions. This was granted in 1261 but the Baronial faction was too strong and so the matter was eventually placed in the hands of Louis IX of France to act as arbitrator. In January 1264 in the Mise of Amiens, Louis annulled the Provisions of Oxford. The decision ignited the Second Barons War (1264-7) with the rebel forces being headed by Simon de Montfort, Earl of Leicester."