When the Abbasid caliphs took over, one of the Ummayads escaped to Spain, and ruled it as an emirate (province). Later it became an independent caliphate. Eventually, though, political power fell to various local rulers, and so the caliphate disintegrated into petty states, of which the Abbadids are one. The same sort of thing had happened in the east, too - by 800 it makes more sense to talk about emirates than caliphates as political units. |