The first great Muslim dynasty of Arab leaders (caliphs) to rule the Empire of the Caliphate, 661-750 AD, descended from a Meccan merchant who became a prominent administrator under the Prophet Muhammad. Headed by Abu Sufyan, the Umayyads were a tribe centered in Mecca who initially resisted Islam but finally converted in 627. In the first Muslim civil war (656-661) Abu Sufyan's son Mu'awiyah emerged victorious over 'Ali, Muhammad's son-in-law and fourth caliph; Mu'awiyah then established himself as the first Umayyad caliph. The Umayyads were supplanted by the Abbasids in 750.