The dynasty of caliphs who governed the Islamic Empire from 750 until 1258 CE.
The Abbasid Dynasty was founded on two disaffected Islamic populations: non-Arabic Muslims and Shi'ites. For the most part, the Islamic impetus to the Abassid revolution lay in the secularism of the Umayyad caliphs. The Umayyads had always been outsiders—as a wealthy clan in Mecca, they had opposed Muhammad—and the secularism and sometime degeneracy that accompanied their caliphate delegitimized their rule for many devout Muslims. The Abassids took their name from al-'Abbas, a paternal uncle of Muhammad and early supporter of the Prophet. Their close kinship to Muhammad and the position of al-'Abbas as a Companion of the Prophet served them well in gaining support. As early as 718 AD, during the reign of Umar II, Muhammad ibn 'Ali, a great-grandson of al-'Abbas, began to proselytize in Persia to rally support for returning the caliphate to the family of the Prophet, the Hashimites.