[dubious – discuss] The Albigensian Crusade was initiated in the Kingdom of France at the behest of Pope Innocent III.

Its purpose was to squash the growing Cathar movement, a religious sect challenging the teachings of the Catholic Church.

[3] The retinue of professional soldiers, mercenary bands (routiers), and pilgrims, assembled and departed from Lyon in early July 1209, beginning the Albigensian Crusade.

[8] He attempted to negotiate with the Crusader army at Montpellier, absolving himself of the things that happened in his domain because of his youth, he was 24 at the time, and declaring his loyalty to the Church.

[10][11] According to the chronicler Peter of Vaux-de-Cernay, the city was "entirely infected with the poison of heresy" and its people were "brimful of every kind of sin".

William says that it was because he felt his presence was needed in Carcassonne and that the people of Béziers could adequately resist the Crusaders without him.

Historian Laurence Marvin feels that because of Raymond Roger's subsequent stout defense of Carcassonne, William's explanation is more likely.

[14] Commanded by the Papal legate, the Abbot of Citeaux, Arnaud Amalric,[15] the Crusader army reached the outskirts of Béziers on 21 July.

Delay would give Raymond Roger time to organize his defenses and increase the likelihood that the army would run out of supplies or drift apart.

[18] That morning, a group of either soldiers or perhaps merely armed civilians from the town made a sortie exiting the gate overlooking the river Orb.

For mark well what these wretched creatures did, in their vast ignorance and folly: out they went, waving their coarse, white linen banners, shouting at the tops of their voices, and thinking to scare the enemy thus, as one might scare birds on a wheatfield-bawling and hallooing, and waving their flags, and all this at crack of dawn, as soon as it was light.

In retaliation, the angry and disappointed routiers burned down buildings, destroying most of the plunder, and the Crusaders were quickly forced to leave the ruined town.

Amalric's own version of the siege, described in his letter to Pope Innocent in August 1209 (col.139), states: Indeed, because there is no strength nor is there cunning against God, while discussions were still going on with the barons about the release of those in the city who were deemed to be Catholics, the servants and other persons of low rank and unarmed attacked the city without waiting for orders from their leaders.

The abbot, like the others, was afraid that many, in fear of death, would pretend to be Catholics, and after their departure, would return to their heresy, and is said to have replied "Caedite eos.

[25] The Crusaders allowed the routiers to rampage and kill without restraint, sparing neither women nor children, but swiftly put a stop to looting.

[4] Amalric's account of the death of 20,000 was probably exaggerated, like Peter of Vaux-de-Cernay's report that 7,000 were slain in the Church of St Magdalene.

Carcassonne fell within a month and Raymond-Roger Trencavel died in captivity later that year, his lands being given to de Montfort.

[21] The war became protracted, and eventually the French king entered the conflict and took control over the Languedoc, leading to the gradual extermination of the Cathar movement.