Descendants of ‘Abbās (d. a.d. 653), uncle of Muḥammad the prophet of islam; in a.d. 750 they seized the office of caliph earlier held by the umayyads, and reigned at Baghdad until 1258.
As Muḥammad's surviving uncle and head of his clan, ‘Abbās would have had a claim to succeed the Prophet after his death in 632, had not ‘Abbās's delayed conversion to Islam counted against him. His son ‘Abdallāh (d. 687), a prominent religious authority, was governor of Basra under ali (‘alĪ ibn abĪ ṬĀlib), but later was won to the cause of Mu’āwiya.
The family played no public role under Mu’āwiya's family, the Umayyads, but they were able by clandestine religious-political propaganda to turn to their advantage the social unrest of the early Arab Muslim Empire. Their message was egalitarian and messianic and seems to have incorporated certain Iranian religious ideas palatable to the newly converted. It was discreetly directed by agents in Kufa, the stronghold of Shī’ī sympathies in Iraq. Under the able Iranian propagandist Abū Muslim, ‘Abbāsid propaganda found greatest response among the half-Islamized Iranian inhabitants of the old eastern marches of the Persian Empire, Khurasan, a frontier area where Zoroastrianism, Buddhism, Mazdakism, Manichaeism, and Nestorian Christianity had met and mixed. Here in 747 local revolts were raised that, by calling for "an Imām [religious leader] of the Prophet's family," grew by 749 into a general rebellion of all disaffected elements in the Umayyad Empire. Shī’īs participated enthusiastically in the belief that a descendant of ‘Alī would come to power, but it was the head of the ‘Abbāsid House, Abū al-‘Abbās al-Saffāḥ (d. 754) who was acclaimed caliph in 749, and who rooted out the Umayyads in every province but Spain.
Like other revolutionary regimes, the ‘Abbāsids had, when once in power, to reckon on conflicts with the differing groups and interests that had cooperated to give them the victory. Under al-Manṣūr, brother and successor of al-Saffāḥ, the new regime's power was consolidated. Abū Muslim was put to death and his closest followers crushed. The hostility of the Shī’īs pursued the dynasty through all its history, and succeeding ‘Abbāsids were alternately led to employ repression or placation in dealing with them.
Al-Manṣ ūr's new capital on the Tigris, Madīnat al-Salam (popularly known as Baghdad, after an earlier village on that site), was built at the junction of several trade routes, and within 50 years had become one of the great centers of civilization.
With the ‘Abbāsid accession, the transformation of the Islamic polity from an Arab kingdom to the Muslim Empire was completed. The economic base of the dynasty was Mesopotamia, seat of earlier multiracial Middle Eastern empires; it drew heavily on the skills and traditions of the conquered peoples, particularly of converted members of the Sassanian bureaucratic class, and it depended on the military support of the peoples of the eastern frontier. Islamic religion and the Arabic language gave their distinctive stamp to this richly syncretic civilization, but the Arabs had lost their exclusive right to the responsibilities and rewards of empire. Islam, not Arab origin, sufficed for full membership in the Empire, and advancement depended almost solely on the favor of the caliphs, who had now transformed the simplicity of the first caliphs into the elaborate and splendid court of Persian autocrats.
The rapidity with which the cultural brilliance of the ‘Abbāsid prime was reached (under Harūn al-Rashīd, 786–809, and his son al-Ma’mūn, d. 833) led Prof. Arnold Toynbee to argue convincingly that in fact under the aegis of Islam the earlier civilization of Achaemenid times had come again into its own.
However, during the subsequent period (836–92) when the court resided at Samarra, a new royal city north of Baghdad, the caliphs became the virtual prisoners of the elite corps they had formed from Central Asian Turkish slaves. Local rulers asserted themselves in the provinces, the clash of new cultural ideas prepared the way for new heretical movements, and a slave uprising of Africans devastated lower Iraq. Caliphal authority was slowly reasserted after 870, but during the long reign of al-Muqtadir (908–32) the central administration of the empire began a period of self-strangulation through corruption and internal rivalries. In 909 the Isma’īlī Shī’īs established an anticaliphate "of the Children of Fāṭima" in Tunisia (capital at Cairo from 969–1171). From 945 to 1055 the ‘Abbāsids at Baghdad were puppets of the Buwayhid dictators, Persian Shī’īs of the "Twelver" sect. From 1055 to c. 1194 they were under the patronage of sultans of the house of Seljuk, Turkish chiefs whom they invited to rid them of the Buwayhids. The seljuks were at least orthodox in practice and led a Sunnī restoration.
In religious as well as imperial theory the caliph was still the sole fount of all validly exercised power, and most Sunnī Muslim monarchs found it advisable to secure a diploma of investiture from Baghdad. This has led to the caliphate's being rather inaccurately likened to the papacy.
A brief restoration of ‘Abbāsid power, in Iraq at least, occurred with the passing of the Seljuks, under the Caliph al-Nāṣir (1180–225). But in 1258 Hulagu, grandson of Genghis Khan, destroyed Baghdad and put the Caliph al-Musta‘ṣim to death.
Under the Mamelukes of Cairo, a member of the ‘Abbāsid family was established as caliph there in 1261. This shadow caliphate was continued by his descendants until the end of the sultanate in 1517, but it was only a legal device for the legitimization of Muslim rulers, and the Cairo ‘Abbāsids were little more than court officials.
Bibliography: p. k. hitti, History of the Arabs (6th ed. New York 1958). w. muir, The Caliphate, Its Rise, Decline and Fall, rev. t. h. weir (Edinburgh 1924). a. j. toynbee, A Study of History, 12 v. (New York 1948–61). b. lewis, The Arabs in History (New York 1950); Encyclopedia of Islam, ed. b. lewis et al. (2d ed. Leiden 1954–) 1:15–23.
[j. a. williams]