Abbasid was the dynastic name generally given to the caliphs of Baghdad, the second of the two great dynasties of the Muslim empire. The Abbasid caliphs officially based their claim to the throne on their descent from Abbas (AD 566-652), the eldest uncle of Muhammad, in virtue of which descent they regarded themselves as the rightful heirs of the Prophet as opposed to the Umayyads, the descendants of Umar.
Throughout the second period of the Umayyads, representatives of this family were among their most dangerous opponents, partly by the skill with which they undermined the reputation of the reigning princes by accusations against their orthodoxy, their moral character and their administration in general, and partly by their cunning manipulation of internecine jealousies among the Arabic and non-Arabic subjects of the empire.
In the reign of Marwan II this opposition culminated in the rebellion of Ibrahim the Imam, the fourth in descent from Abbas, who, supported by the province of Khorasan, achieved considerable successes, but was captured (AD 747) and died in prison (as some hold, assassinated). The quarrel was taken up by his brother Abdallah, known by the name of Abu al-'Abbas as-Saffah, who after a decisive victory on the Greater Zab river (750) finally crushed the Umayyads and was proclaimed caliph.
The history of the new dynasty is marked by perpetual strife and the development of luxury and the liberal arts, in place of what their opponents identified as old-fashioned austerity of thought and manners. Mansur, the second of the house, who transferred the seat of government to the new city of Baghdad, fought successfully against the peoples of Asia Minor, and the reigns of Harun al-Rashid (786--809) and al-Ma'mun (813-833) were periods of extraordinary splendour.
Independent monarchs established themselves in Africa and Khorasan (an Umayyad prince had set up independent rule in Spain), and in the north-west the Byzantines successfully encroached.
The ruin of the dynasty came, however, from those Turkish slaves who were constituted as a royal bodyguard by al-Mu'tasim (833-842). Their power steadily grew until al-Radi (934-941) was constrained to hand over most of the royal functions to Mahommed b. Raik. Province after province renounced the authority of the caliphs, who became figureheads, and finally Hulagu Khan, the Mongol general, sacked Baghdad (February 28 1258) with great loss of life.
The Abbasids still maintained a feeble show of authority, confined to religious matters, in Egypt under the Mamelukes, but the dynasty finally disappeared with Motawakkil III, who was carried away as a prisoner to Constantinople by Selim I.
See also History of Islam
Initial text from 1911 encyclopedia -- Please update as needed
Abbasid Caliphs of Baghdad
Abbasid Caliphs in Cairo
