The Albigensian Crusade
Phase Three: Aragon
Peter of Aragon, King of Aragon, was also suzerain of some lands in France. He was trying to preserve and extend his holding without looking like a heretic or a supporter of heretics. Simon's conquests endangered Peter's interests. His attempts at conciliation were rebuffed, so he threw in with Raymond.
The two invest Muret, twelve miles south of Toulouse. Raymond advises caution, Peter wants to attack, so Raymond refused to participate.
12 September 1213, Battle of Muret. Peter attacks with knights alone, leaving the Toulousain militia still assaulting the walls of the city. The crusaders caught the allies unprepared; Simon flanks them. Peter, dressed in ordinary armor, is killed because no one recognized him. Then, Simon falls upon the unsuspecting foot, slaughtering them.
Aragon is eliminated as a factor. It was the only major power that could oppose the French crusaders.