The Umayyad Caliphate or the Umayyad Empire (US: ; Arabic: ٱلْخِلَافَة ٱلْأُمَوِيَّة, romanized: al-Khilāfa al-Umawiyya) was the second caliphate established after the death of the Islamic prophet Muhammad and was ruled by the Umayyad dynasty from 661 to 750. It succeeded the Rashidun Caliphate, of which the third caliph, Uthman ibn Affan, was also a member of the Umayyad clan. The Umayyad family established hereditary rule under Mu'awiya ibn Abi Sufyan, the long-time governor of Greater Syria, who became caliph after emerging victorious in the First Fitna following the assassination of Ali in 661. Syria remained the Umayyads' core power base thereafter, with Damascus as their capital. After Mu'awiya's death in 680, Umayyad authority was challenged in the Second Fitna, during which the Sufyanid line was replaced in 684 by Marwan ibn al-Hakam, who founded the Marwanid line that restored Umayyad rule over the Caliphate. The Umayyads continued the early Muslim conquests, conquering the Maghreb, Transoxiana, Sindh and Hispania. At its greatest extent, the Umayyad Caliphate covered an area of 11,100,000 km2 (4,300,000 sq mi), making it one of the largest empires in history in terms of geographical size. The dynasty was overthrown by the Abbasids in 750. Survivors of the Umayyad dynasty established an emirate and then a caliphate in al-Andalus with its capital at Córdoba, which became a major centre of science, medicine, philosophy and invention during the Islamic Golden Age. The Umayyad Caliphate ruled over a vast multiethnic and multicultural population.