Abbasid Caliph

The Abbasid caliphs were the holders of the Islamic title of caliph who were members of the Abbasid dynasty, a branch of the Quraysh tribe descended from the uncle of the Islamic prophet Muhammad, al-Abbas ibn Abd al-Muttalib.

The family came to power in the Abbasid Revolution in 748–750, supplanting the Umayyad Caliphate. They were the rulers of the Abbasid Caliphate, as well as the generally recognized ecumenical heads of Islam, until the 10th century, when the Shi'a Fatimid Caliphate (established in 909) and the Caliphate of Córdoba (established in 929) challenged their primacy. The political decline of the Abbasids had begun earlier, during the Anarchy at Samarra (861–870), which accelerated the fragmentation of the Muslim world into autonomous dynasties. The caliphs lost their temporal power in 936–946, first to a series of military strongmen, and then to the Shi'a Buyid dynasty that seized control of Baghdad; the Buyids were in turn replaced by the Sunni Seljuk Turks in the mid-11th century, and Turkish rulers assumed the title of "Sultan" to denote their temporal authority. The Abbasid caliphs remained the generally recognized suzerains of Sunni Islam, however. In the mid-12th century, the Abbasids regained their independence from the Seljuks, but the revival of Abbasid power ended with the Sack of Baghdad by the Mongols in 1258.

In 1261, the Abbasid caliphate was re-established by a cadet branch of the dynasty at Cairo, under the auspices of the local Mamluk sultans. Once again, the caliph was a purely religious and symbolic figure, while temporal power rested with the Mamluks. The revived Abbasid caliphate lasted until the Ottoman conquest of Egypt in 1517, after which the caliphal title passed to the Ottoman dynasty.

...
Wikipedia