Abbasid Caliphate Founded
In 750 AD the Abbasid dynasty overthrew the Umayyad Caliphate and took control of the Islamic world's largest political order. The change of rulers did more than swap one family for another. It shifted the empire's center of gravity eastward, opened power to a wider range of Muslims, and set the stage for a period of extraordinary cultural and intellectual activity. One note on the summary: Baghdad was not founded in 750 but about 762, under the second Abbasid caliph, al-Mansur.
The Umayyads, who ruled from Damascus from 661, had built an empire stretching from Spain and North Africa to Central Asia. But resentment grew. Many non-Arab converts, especially in Persian-speaking Khurasan, felt treated as second-class members of the community. Some Muslims also thought the Umayyads were worldly and illegitimate, and favored leadership by someone from the family of the Prophet Muhammad. The Abbasids, descendants of Muhammad's uncle al-Abbas, drew on this discontent with a broad, deliberately vague message promoting a ruler from the Prophet's house.
The movement gathered strength in Khurasan during the 740s, where the general Abu Muslim organized a rebellion under black banners. Abbasid forces defeated the Umayyad caliph Marwan II at the Battle of the Zab in early 750, and he was later killed in Egypt. Abu al-Abbas, known as al-Saffah, was proclaimed caliph. The new rulers hunted down much of the Umayyad family, though one survivor, Abd al-Rahman, escaped to Spain and founded a separate Umayyad state in al-Andalus. Abu Muslim himself was later executed on the orders of al-Mansur, a sign of how the dynasty dealt with powerful allies.
Al-Mansur's founding of Baghdad around 762, on the Tigris River, gave the dynasty a new capital close to Persian lands and major trade routes. The city grew into one of the largest in the world. Under caliphs such as Harun al-Rashid and al-Ma'mun, Baghdad became a hub of scholarship. The translation movement rendered Greek, Persian, Indian, and Syriac works into Arabic, and the often-cited House of Wisdom is associated with this effort, although historians debate how formal an institution it actually was. Scholars like al-Khwarizmi in mathematics, and thinkers in medicine, astronomy, and philosophy, built on inherited knowledge and added their own.
Abbasid political unity did not last. Provinces such as Spain, and later Egypt and Iran, slipped into the hands of independent dynasties, and from the 9th century the caliphs increasingly became figureheads under military commanders. The caliphate survived in name until the Mongols sacked Baghdad in 1258. Even so, the cultural legacy of the Abbasid age shaped science, literature, and religion across the Islamic world and beyond, including medieval Europe.