ad-Din Abu'l-Ma'āli. In that same year, Louis IX of France embarked on the Seventh Crusade in Egypt. He captured the port of Damietta from the aging al-Salih Ayyub which he refused to turn over to Conrad II, who had inherited the throne of Jerusalem from his parents Frederick II and Isabella II. The Frankish Crusaders were soundly defeated by Abu Futuh Baibars, then a commander in the Egyptian army, at the battle of al-Mansurah in 1250. Saint Louis, as Louis IX was known, was captured by the Egyptians and, after a handsome reward was paid, spent four years in Acre, Caesarea and Jaffa. One of the captives with Louis was Jean de Joinville, biographer of the king, who reported the interaction of the monarch with the Assassins. While at Acre, emissaries of Radi ad-Din Abu'l-Ma'āli met with him, demanding a tribute be paid to their chief "as the emperor of Germany, the king of Hungary, the sultan of Egypt and the others because they know well they can only live as long as it please him." Alternately, the king could pay the tribute the Assassins paid the Templars and Hospitallers. Later the king's Arabic interpreter Yves the Breton met personally with Radi ad-Din and discussed the respective beliefs. Afterwards, the chief da'i went riding, with his valet proclaiming: "Make way before him who bears the death of kings in his hands!" The Egyptian victory at al-Mansurah led to the establishment of the Mamluk dynasty in Egypt. Muhammad III was murdered in 1255 and replaced by his son Rukn al-Din Khurshah, the last Imam to rule Alamut. Najm ad-Din later became chief da'i of the Assassins in Syria, the last to be associated with Alamut. Louis IX returned to north Africa during the Eighth Crusade where he died of natural causes in Tunis. Downfall and aftermath The Assassins suffered a significant blow at the hands of the Mongol Empire during the well-documented invasion of Khwarazm. A decree was handed over to the Mongol commander Kitbuqa who began to assault several Assassin fortresses in 1253 before Hulagu's advance in 1256, seizing Alamut late that year. Lambsar fell in 1257, Masyaf in 1267. The Assassins recaptured and held Alamut for a few months in 1275, but they were crushed and their political power was lost forever. Rukn al-Din Khurshah was put to death shortly thereafter. Though the Mongol massacre at Alamut was widely