ABBASIDS  , the name generally given to the caliphs of

Bagdad, the second of the two great dynasties of the Mahommedan em-pire . The Abbasid caliphs officially based their claim to the throne on their descent from Abbas (A.D . 566—652), the eldest uncle of Mahomet, in virtue of which descent they regarded themselves as the rightful heirs of the Prophet as opposed to the Omayyads, the descendants of Omayya . Throughout the second period of the Omayyads, 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 Merwan 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 (A.D . 747) and died in prison (as some hold, assassinated) . The quarrel was taken up by his brother Abdallah, known by the name of Abu'l-Abbas as-Saffah, who after a decisive victory on the Greater Zab (750) finally crushed the Omayyads 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 the old-fashioned austerity of thought and manners . Mansur, the second of the house, who transferred the seat of government to Bagdad, fought successfully against the peoples of Asia Minor, and the reigns of Harun al-Rashid (786—809) and Mamun (813—833) were periods of extraordinary splendour . But the empire as a whole stagnated and then decayed rapidly . Independent monarchs established themselves in Africa and Khorasan (Spain had remained Omayyad throughout), and in the north-west the Greeks successfully encroached . The ruin of the dynasty came, however, from those Turkish slaves who were constituted as a royal bodyguard by Moqtasim (833—842) .

Their

power steadily grew until 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 were merely lay figures, and finally Hulagu, the Mongol chief, burned Bagdad (Feb . 28th, 1258) . 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 CALIPHATE (Sections B, 14 and C), where a detailed account of the dynasty will be found .