The Cathars were especially numerous in southern France, in the region of Languedoc, then part of the Catalan-Aragonese Confederation or Kingdom of Aragon. They were termed Albigensians because of the movement's presence in and around the city of Albi. Political control in Languedoc was split amongst many local lords and town councils, the area was relatively lightly oppressed and reasonably advanced.
The crusading efforts can be divided into a number of periods, the first from 1209 to 1215 was a series of great success for the crusaders in Languedoc. The captured lands however were largely lost between 1215 and 1225 in a series of revolts and reverses. The situation turned again following the intervention of the French king, Louis VIII, in 1226. He died in November of that year, but the efforts continued under Louis IX; the area was reconquered by 1229 and main protagonists made peace. From 1233 the efforts of the Inquisition to crush Catharism were key, there was resistance and revolts with the military action finally ending in 1255 but the Cathar efforts were clearly doomed.
Pope Innocent III organised the vigorous suppression of the Cathars. He sent a papal legate to investigate Languedoc in 1204 and found that it would be difficult to convert the heretics. The Pope called upon the French king, Philippe II, to act against those nobles who permitted Catharism, but Philippe was involved in the Bouvines War and declined to act. In 1206 the Pope sought support for action from the nobles of Languedoc. The powerful count Raymond VI of Toulouse refused to assist and was excommunicated in May, 1207. Raymond met with a papal representative, Pierre de Castelnau, in January 1208, and after an angry meeting Pierre de Castelnau was killed the following day. The Pope reacted to the affront by a bull declaring a crusade against Languedoc