The Abbasieds were the dynasty of caliphs who ruled the Islamic Empire from 750 until the Mongol conquest of the Middle East in 1258. The dynasty takes its name from its ancestor al-Abbas, the uncle of the Prophet Muhammad صلى الله عليه وسلم. In 750 the Abbasids defeated the Umayyads and transferred the capital of the Caliphate from Damascus to Baghdad, thereby shifting the empire's center from Syria to Iraq.
The Abbasied period may be divided into two parts. In the period from 750 to 945 the authority of the caliphs gradually declined, while the Turkish military leaders gained increasing influence. The dynasty's power peaked in the reign (786-809) of Harun Al-Rashid. In the later period, from 945 to 1258, the caliphs generally held no more than nominal suzerainty; real power, even in Baghdad, passed to dynasties of secular sovereigns.
The Abbasieds' 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.