The Abbasid Caliphate: Baghdad's Golden Age, Fragmentation, and the Mongol Sack of Baghdad

The Abbasid family, claiming descent from an uncle of Muhammad, led the revolution that overthrew the Umayyads, and Abu al-Abbas as-Saffah was proclaimed the first Abbasid caliph in 749. In 762 the second Abbasid caliph, Abu Ja'far al-Mansur, founded an entirely new capital on the Tigris, Baghdad, laid out as a circular city known as Madinat al-Salam, "the City of Peace," shifting the political center of gravity of the Islamic world decisively toward Iraq and Persian administrative traditions.