The Umayyad Caliphate: Damascus and a Vast Empire

Muawiya ibn Abi Sufyan founded the Umayyad dynasty in 661, moving the capital from Medina to Damascus and transforming what had been an elective caliphate into a hereditary one by securing an oath of allegiance for his son Yazid I as heir. The dynasty ruled from Damascus as amir al-mu'minin over an empire administered through provincial governors, a land-tax register called the diwan al-kharaj, and a combined postal and intelligence service, the diwan al-barid, while continuing to rely heavily on the Christian and Persian officials inherited from the Byzantine and Sasanian administrations it replaced.