Abbasid (əbă´sĬd, ă´bəsĬd) or Abbaside (–sīd, –sĬd), Arab family descended from Abbas, the uncle of Muhammad. The Abbasids held the caliphate from 749 to 1258, but they were recognized neither in Spain nor (after 787) W of Egypt. Under the Umayyad caliphs the Abbasids lived quietly until they became involved in numerous disputes, beginning early in the 8th cent. The family then joined with the Shiite faction in opposing the Umayyads, and in 747 the gifted Abu Muslim united most of the empire in revolt against the Umayyads. The head of the Abbasid family became caliph as Abu al-Abbas as-Saffah late in 749. The last Umayyad caliph, Marwan II, was defeated and killed and the Umayyad family nearly exterminated; one surviving member fled to Spain, where the Umayyads came to rule. Under the second Abbasid caliph, called al-Mansur (see Mansur, al-, d. 775), the capital was moved from Damascus to Baghdad, and Persian influence grew strong in the empire. The early years of Abbasid rule were brilliant, rising to true splendor under Harun ar-Rashid, the fifth caliph, and to intellectual brilliance under his son al-Mamun (see Mamun, al-), the seventh caliph. After less than a hundred years of rule, however, the slow decline of the Abbasids began. Long periods of disorder were marked by assassinations, depositions, control by Turkish soldiers, and other disturbances, and from the beginning of their reign there were rival caliphs (see caliphate). In 836 the capital was transferred to Samarra, remaining there until 892. Under the later Abbasids, the power of the caliphate became chiefly spiritual. Many independent kingdoms sprang up, and the empire split into autonomous units. The Seljuk Turks came to hold the real power at Baghdad. The conquests of Jenghiz Khan further lowered the prestige of the Abbasids, and in 1258 his grandson Hulagu Khan sacked Baghdad and overthrew the Abbasid caliphate. The 37th caliph died in the disaster, but a member of the family escaped to Cairo, where he was recognized as caliph (see Mamluks). The Cairo line of the Abbasid caliphate, completely subordinated to the Mamluks, survived until after the Ottoman conquest (1517) of Egypt.
See M. A. Shaban, The Abbāsid Revolution (1970); H. Kennedy, The Early Abbasid Caliphate (1981).