Title given to those who succeeded the Prophet Muhammad as real or nominal ruler of the Muslim world, ostensibly with all his powers except that of prophecy. Controversy over the selection of the fourth caliph, 'Ali, eventually split Islam into the Sunnite and Shi'ite branches. 'Ali's rival, Mu'awiyah I, established the Umayyad dynasty of caliphs, which produced 14 caliphs (661–750). The 'Abbasid dynasty (750–1258), the most widely observed caliphate, associated with 38 caliphs, moved the capital from Damascus to Baghdad. The Mongol conquest of Baghdad in 1258 effectively ended the dynasty. Other Muslim leaders created caliphates with limited success. The Fatimid dynasty proclaimed a new caliphate in 920; 'Abd al-Rahman III announced one in opposition to both the 'Abbasids and the Fatimids in 928. A scion of the 'Abbasid line was set up by the Mamluk dynasty as a sort of puppet caliph after 1258. This caliphate exercised no power whatsoever, and, from 1517 until it was abolished by the Republic of Turkey in 1924, it resided in Istanbul under the control of the Ottoman Empire. Modern Muslim militants consider the abolition of the caliphate a catastrophic event, and its return has been a central pillar of their political program.