Don Sancho, having meantime assumed all three crowns, became anxious to dispossess his sister of Zamorra.  But the Cid refused to take part in so unchivalrous a deed, and thereby so angered the king that he vowed he would exile him.  When the Cid promptly rejoined that in that case he would hasten to Toledo and offer his services to Alfonso to help him recover all he had lost, Sancho repented and apologized.  He did not, however, relinquish his project of despoiling his sister of Zamorra, but merely dispensed the Cid from accompanying him.

Because Zamorra was well defended by Vellido Dolfos,—­the princess’ captain,—­King Sancho was not able to take it.  He so sorely beset the inhabitants, however, that Vellido Dolfos resolved to get the better of him by strategy.  Feigning to be driven out of the city, he secretly joined Don Sancho, and offered to deliver the city into his hands if the king would only accompany him to a side gate.  Notwithstanding adverse omens, the credulous Sancho, believing him, rode off, only to meet his death at the postern gate, inside of which his murderer immediately took refuge.

On learning that his master has been slain, the Cid hastened to avenge him, and, as Sancho had left no heir, proclaimed Alfonso his successor.  We are told that this young prince had already heard of his brother’s death through a message from his sister, and, fearing the Moors would not allow him to depart for good, had merely asked permission to visit his kin.  The wary Moorish king consented, but only on condition Alfonso would promise never to attack him or his sons, should he become king.

When Alfonso arrived at Zamorra, all the Spaniards readily did homage to him save the Cid, who refused to have anything to do with him until he had solemnly sworn he had no share in his brother’s death.  To satisfy the Cid, therefore, Alfonso and twelve of his men took a threefold oath in the church of Burgos; but it is said Alfonso never forgave the humiliation which the Cid thus inflicted upon him.

The new monarch proved to be a wise ruler for the kingdoms of Leon, Castile, Gallicia, and Portugal.  He was not without his troubles, however, for shortly after his succession the Cid quarrelled with one of his nobles.  Next the Moorish kings became disunited and Alfonso’s former host summoned him to his aid.  Not only did Alfonso assist this king of Toledo, but invited him into his camp, where he forced him to release him from the promise made on leaving his city.  Not daring to refuse while in the power of the Christians, the Moorish king reluctantly consented, and was surprised and delighted to hear Alfonso immediately renew the oath, for, while not willing to be friends with the Moors under compulsion, he had no objection to enter into an alliance with them of his own free will.