The Albigensian Crusade was initiated by the Kingdom of France at the behest of Pope Innocent III . Its purpose was to squash the growing Cathar movement , which flourished mainly in the Languedoc region of southern France . The immediate cause was the killing of the papal legate , Pierre de Castelnau . The Crusaders set out in the summer of 1209 . After several military victories , they were able to capture many towns without a fight before arriving at Minerve . After the fall of Carcassonne , papal legate Arnaud Amalric , who had led troops during the Massacre at Béziers , was replaced as commander of the Crusader force by Simon de Montfort , 5th Earl of Leicester , although Amalric continued to accompany the army
Massacre at Béziers
Massacre at Béziers
Siege of Minerve