Carcassonne became famous in its role in the Albigensian Crusades, when the city was a stronghold of occitan cathars. In August 1209 the crusading army of Simon de Montfort forced its citizens to surrender. After capturing Raymond-Roger de Trencavel and imprisoning and allowing him to die, Montfort made himself the new viscount. He added to the fortifications. Carcassonne became a border citadel between France and the kingdom of Aragon (Spain).