A major development in the history of Muslim Spain was the dynastic change in 750 in the Arab Caliphate, when an Umayyad Prince escaped the slaughter of his family in Damascus, fled to Cordoba in Spain, and created a new Islamic state in the area. This was the start of a distinctly Spanish Muslim society, where large Christian and Jewish populations coexisted with an increasing percentage of Muslims. There are many stories of descendants of Visigothic chieftains and Roman counts whose families converted to Islam during this period. The at-first small Muslim elite continued to grow with converts, and with a few exceptions, rulers in Islamic Spain allowed Christians and Jews the right specified in the Koran to practice their own religions, though non-Muslims suffered from political and taxation inequities. The net result was, in those areas of Spain where Muslim rule lasted the longest, the creation of a society that was mostly Arabic-speaking because of the assimilation of native inhabitants, a process in some ways similar to the assimilation many years later of millions of immigrants to the United States into English-speaking culture. As the descendants of Visigoths and Hispano-Romans concentrated in the north of the peninsula, in the kingdoms of Asturias/Leon, Navarre and Aragon and started a long campaign known as the 'Reconquista' which started with the victory of the Christian armies in Covadonga in 722. Military campaigns continued without pause. In 1085 Alfonso VI of Castille took back Toledo. In 1212 the crucial Battle of Las Navas de Tolosa meant the recovery of the bulk of the peninsula for the Christian kingdoms. In 1238 James I of Aragon took Valencia. In 1236 the ancient Roman city of Cordoba was re-conquered by Ferdinand III of Castille and in 1248 the city of Seville. The famous medieval epic poem 'Cantar de Mio Cid' narrates the life and deeds of this hero during the Reconquista.