A new crusade was discussed at the Council of Lyon in 1245 by Pope Innocent IV. The council deposed Frederick II, so no help could be expected from the empire, but King Louis IX of France had already vowed to go on crusade. Louis arrived in Cyprus in 1248, where he gathered an army of his own men, including his brothers Robert of Artois, Charles of Anjou, and Alphonse of Poitiers, and those of Cyprus and Jerusalem, led by the Ibelin family John of Jaffa, Guy of Ibelin, and Balian of Beirut. Once again the target was Egypt. Damietta was captured without resistance when the crusaders landed in June 1249, but the crusade halted there until November, by which time the Egyptian sultan Ayyub had died and had been succeeded by his son Turanshah. In February, the crusaders were defeated at the Battle of al-Mansurah, where Robert of Artois was killed. The crusaders were unable to cross the Nile, and, suffering from disease and lack of supplies, retreated towards Damietta in April. They were defeated along the way at the Battle of Fariskur, with Louis being taken captive by Turanshah. During Louis' captivity, Turanshah was overthrown by his Mamluk soldiers, led by the general Aybak, who then released Louis in May in return for Damietta and a large ransom. For the next four years Louis resided in Acre, and helped refortify that city along with Caesarea, Jaffa, and Sidon. He also made truces with the Ayyubids in Syria, and sent embassies to negotiate with the Mongols, who were beginning to threaten the Muslim world, before returning home in 1254. He left behind a large garrison of French soldiers in Acre, under the command of Geoffrey of Sergines.