This unity of plan is consistently preserved by a rearrangement of the true chronology of events and by the introduction of purely traditional episodes. The shifting of historical values may be due to the fact that when the poem was composed, about 1150, the power of the Moor had really been broken by the conquests of Ferdinand I, Alphonso VI, Alphonso VII and Alphonso VIII of Castile and alphonso I, the Battler, of Aragon. The menace was no longer felt with the keenness of an hundred years before, until the end of the tenth century the Moors had dominated the Peninsula. The growth of the Christian states from the heroic nucleus in northern Asturias was confined to the territory bordering the Bay of Biscay, Asturias, Santander, part of the province of Burgos, León, and Galicia. In the East other centers of resistance had sprung up in Navarre, Aragon and the County of Barcelona. At the beginning of the eleventh century the tide turned. The progress of the reconquest was due as much to the disruption of Moorish unity as to the greater aggressiveness and closer coöperation of the Christian kingdoms. The end of the Caliphate of Cordova was the signal for the rise of a great number of mutually independent Moorish states. Sixty years later there were no less than twenty-three of them. By the middle of the following century the enthusiasm that had followed the first successful blows struck against the Moor had waned, and with it the vividness of their historical significance and order. Let us look at the Cid for a moment as he was seen by a Latin chronicler who confesses that the purpose of his modest narrative was merely to preserve the memory of the Cid of history.