sentences:  The Umayyad regime, despite its administrative centralisation, mercenary army and struggle to gain wider social support, could neither harmonise the various ethnic groups inside al-Andalus nor dissolve the old tribes which still organised sporadic ethnic fighting.During the 11th century, the Caliphate's control waned considerably.Provinces broke free from the central Cordoban administration, and became effectively sovereign states — "taifas" — under the same governors that had been named by the last Umayyad Caliphs.