 The Umayyads were overthrown in 750 by a new dynasty, the Abbasids.The first Abbasid caliph, As-Saffah, recruited Shia support in his campaign against the Umayyads by emphasising his blood relationship to Muhammad's household through descent from his uncle, ‘Abbas ibn ‘Abd al-Muttalib.The Shia also believe that he promised them that the Caliphate, or at least religious authority, would be vested in the Shia Imam.