Correct!
Though once on good terms with King Henry III of England, Simon de Montfort could not overlook actions he regarded as unfair and decided Henry was unfit to rule. He led a group of barons in forcing on the king the Provisions of Oxford, a revolutionary governmental reform; then, when Henry refused to abide by the Provisions, Simon ultimately led a baronial rebellion in 1264. He governed England as a military dictator until he was killed in battle a year later.
