The abbasid Caliphate is more simply, the Abbasids (Arabic: العبّاسيّون / ISO 233: al-‘abbāsīyūn), was the third of the Islamic caliphates. It was ruled by the Abbasid dynasty of caliphs, who built their capital in Baghdad after overthrowing the Umayyad caliphs from all but the Al Andalus region.
The Abbasid caliphate was founded by the descendants of the Islamic prophet Muhammad’s youngest uncle, Abbas ibn Abd al-Muttalib, in Harran in 750 CE and shifted its capital in 762 to Baghdad. It flourished for two centuries, but slowly went into decline with the rise to power of the Turkish army it had created, the Mamluks. Within 150 years of gaining control of Persia, the caliphs were forced to cede power to local dynastic emirs who only nominally acknowledged their authority. The caliphate also lost the Western provinces of Al Andalus, Maghreb and Ifriqiya to an Umayyad prince, the Aghlabids and the Fatimids, respectively.
The Abbasids’ rule was briefly ended for three years in 1258, when Hulagu Khan, the Mongol khan, sacked Baghdad, resuming in Mamluk Egypt in 1261, from where they continued to claim authority in religious matters until 1519, when power was formally transferred to the Ottomans and the capital relocated to Constantinople.