SIMON IV of Montfort. – Leader of the Albigensian Crusade. Of an extremely ancient family, son of Simon III, baron of Montfort, he was born in the second half of the 12th century and died near Toulouse on 25 June 1218. In 1199, he took the cross for Palestine with Thibaut of Champagne. Upon his return to France, he was assigned command of the expedition against the Albigensians, which he accepted with great hesitation (1208).
Having assembled a strong army in 1210, he threw himself into the struggle. In 1212 he took Lavaur after a year-long siege, and on 12 September 1213 he won the famous victory at Muret over the combined forces of the Toulousains and Catalans. The King of Aragon was killed and Count Raymond of Toulouse fled. Realizing the knight’s ambition, the Pope declared the Crusade at an end; yet Simon pursued it with even greater zeal than before. Despite the warning of Innocent III, the Fourth Lateran Council, which expressly condemned the Albigensian heresy, confirmed Simon in possession of the county of Toulouse and the duchy of Narbonne (1215). But within a year he was driven out of Toulouse, which declared in favor of Raymond. Simon then proclaimed the need for a new crusade and laid siege to the city, during which he died.