A heresy, which had occurred in the town of Albi, had developed little by little in all the South of France, and the papal legate, charged with making an investigation, had been assassinated (1208).

The pope exhorted Christendom with a crusade against the Albigensians, and all the knighthood of north answered her call: a formidable army gathered in Lyon, and fell down on Béziers: the city was taken by storm, was plundered and burned; all the population was massacred: "Kill to them all, exclaimed a fanatic, God will recognize to them his" 7000 people were burned in a church, and numbers it deaths rose with more than 40 000 (1209).

This appalling war, started under Philippe Auguste, who refused to appear to with it, continued under Louis VIII, who himself took a great part there, and was finished only after him by the Blanche queen of Castille.

The war of the Albigensians was a war of extermination.

Simon de Montfort, who was the principal chief of Cross of 1209 to 1218, announced himself by his fanaticism; he looked at the heretics as vipers which should be crushed, and all those which fell between its hands were flarings sharp, jetés in the wells or hung with the trees of the ways; he saved neither to the women nor the children.

Louis VIII, who directed the crusade after him, seems to have been less cruel; the bishop of Auch obtained the grace of many prisoners.

The tender of the count de Toulouse Raymond VII put an end to the war of the Albigensians.

April 12, 1229, it went to Notre-Dame of Paris, out of shirt and barefoot, like a criminal who walks to the torment, and solemnly swore to be faithful to the Holy Church in the future, to punish the heretics, without saving to his parents nor his friends, to yield to the king a part of his fields, and to shave the walls of Toulouse: "It was pity, known as a chronicler, to see such a man undergoing such a major humiliation"