Umayyad Caliphate

Muawiya, governor of Syria and Ali's opponent at Siffin, took the caliphate in 661 and moved its capital to Damascus. His decisive innovation was to name his son as successor, converting an office that had been conferred by acclamation into a dynasty, and it was that decision that produced the event on which Shia Islam turns. In 680 Husayn, the Prophet's grandson, refused allegiance to the new caliph Yazid and was intercepted with his small following on the plain of Karbala in Iraq, where he and most of his household were killed. The mourning of that day, Ashura, became the central devotional act of Shia Islam and the model of righteous suffering against unjust power.

Abd al-Malik, who reigned from 685 and put down a second civil war, remade the empire's public face. He made Arabic the language of administration in place of Greek and Persian, replaced the borrowed Byzantine and Sasanian coin types with a purely epigraphic Islamic coinage carrying Quranic text and no image, and in 691 or 692 completed the Dome of the Rock in Jerusalem.

That building is the earliest surviving monument of Islamic architecture, and its inscriptions, which affirm God's oneness and address Christians directly on the status of Jesus, are the first public statement of Islam as a religion distinct from those around it rather than a movement inside them.

The empire reached its greatest extent under the Umayyads, from the Iberian peninsula after 711 to the Indus and the edge of Central Asia, and the failure of the sieges of Constantinople in the 670s and again in 717 and 718 fixed the frontier with Byzantium for centuries. Governing it exposed a contradiction the dynasty never resolved. Islam admitted converts on equal terms; the Umayyad fiscal system, built on Arab soldiers drawing stipends from the taxes of conquered non-Arabs, did not. Non-Arab converts, the mawali, found themselves still paying the taxes of subject peoples and excluded from the honours of the conquerors, and their grievance became the strongest current running against the dynasty.

Religious opposition took several forms at once. Kharijite revolts recurred across Iraq and Arabia on the principle that a sinful ruler forfeits authority; Shia risings appealed to the memory of Karbala; and pious scholars in Medina and Iraq, the ancestors of the ulama, criticised the caliphs as worldly kings rather than successors of the Prophet, a judgement that shaped how later Sunni historians wrote about them.

The revolution that began in Khurasan in 747 gathered all of it and destroyed the dynasty in 750. One grandson escaped to Spain, founded an emirate at Cordoba, and began the great mosque there in 785; his line took the caliphal title in 929 and lasted until 1031.