By the middle of the thirteenth century, the bishops under Pope Innocent met to again deal with the Cathar “problem.” Catharism had become entrenched in the French towns of Albi, Toulouse, and Carcassonne and was spreading its Gnostic heresies. The Pope and his bishops decided to establish the Inquisition for the purpose of permanently exterminating the Cathars, their ideas, and their movement. The Roman Catholic Church set up inquests in various districts, making it easier to find, try, and punish heretics. Another massacre of Cathars took place in Monteségur when two hundred Perfecti were burned in a massive bonfire near the base of the castle located there. The Church also meted out severe punishments for noblemen and anyone suspected of being a Cathari sympathizer. The Cathars who eluded detection went into hiding and scattered far and wide. The Inquisition maintained records of those it executed and so historians know that the last Cathar Perfecti was put to death in A.D. 1321.

Some historians refer to the massacre of Cathars as the Albigensian Crusade. The Crusades normally were thought of as military expeditions (holy wars) launched during the eleventh, twelfth, and thirteenth centuries to reclaim sacred places such as Jerusalem and the Holy Land from Muslim tyranny. But since that time the term, according to the dictionary, has broadened to encompass a vigorous, aggressive movement to defend an idea or cause.