The Barons' War was a conflict in England during the 13th century, primarily from 1264 to 1267. It arose from discontent among the barons against the rule of King Henry III. The barons sought to limit the king's power and restore the provisions of the Magna Carta, which had been established in 1215 to protect their rights. Led by Simon de Montfort, the barons initially achieved significant victories, including the capture of London. However, the conflict ultimately ended with the defeat of the barons, leading to the restoration of royal authority and the eventual establishment of a more centralized monarchy under Henry III.