The First Crusade, called in response to a request for help from the Byzantine emperor Alexius Comnenus, was astonishingly successful. The Crusaders conquered Nicaea (in Turkey) and Antioch and then went on to seize Jerusalem, and they established a string of Crusader-ruled states. However, after the Muslim leader Zangī captured one of them, the Second Crusade, called in response, was defeated at Dorylaeum (near Nicaea) and failed in an attempt to conquer Damascus. The Third Crusade, called after the sultan Saladin conquered the Crusader state of Jerusalem, resulted in the capture of Cyprus and the successful siege of Acre (now in Israel), and Richard I’s forces defeated those of Saladin at the Battle of Arsūf and at Jaffa. Richard signed a peace treaty with Saladin allowing Christians access to Jerusalem. The Fourth Crusade—rather than attacking Egypt, then the centre of Muslim power—sacked the Byzantine Christian city of Constantinople. None of the following Crusades were successful. The capture of Acre in 1291 by the Māmluk sultan al-Ashraf Khalil marked the end of Crusader rule in the Middle East.