How did the Albigensian Crusade change political control of southern France?

The Albigensian Crusade fundamentally transformed the political landscape of southern France by dismantling the autonomy of its regional nobility and consolidating royal power.12

Before the conflict, the region was characterized by a degree of independence, with local lords—most notably the counts of Toulouse—providing protection and tolerance to the Cathari, a religious group the Roman Catholic Church deemed heretical. The Crusade, initiated by Innocent III, pitted the northern French nobility against their southern counterparts.13

While the war initially saw northern leaders like Simon de Montfort capture significant territory, the conflict ultimately facilitated the intervention of the French crown. King Louis VIII restored northern control in 1226, and the subsequent Treaty of Paris in 1229 effectively ended the independence of southern princes. Under the treaty, the ancestral lands of the house of Toulouse were slated to pass to the Capetian royal house, marking the definitive establishment of French royal authority over the south.123