Then King Don Sancho went to Burgos, because it was the season for besieging a town, being winter. And he sent his letters through all the land, calling upon his vassals to assemble together upon the first day of March in Sahagun, upon pain of forfeiting his favour. And they assembled together in Sahagun on the day appointed; and when the king heard in what readiness they were, it gladdened him, and he lifted up his hands to God and said, Blessed be thy name, O Lord, because thou hast given me all the kingdoms of my father. And when he had said this he ordered proclamation to be made through the streets of Burgos, that all should go forth to protect the host and the body of the king their lord. They made such speed that in five days they arrived before Zamora, and pitched their tents upon the banks of the Douro. And he mounted on horseback with his bidalgos and rode round the town, and beheld how strongly it was situated upon a rock, with strong walls, and many and strong towers, and the river Douro running at the foot thereof; and he said unto his knights, Ye see how strong it is, neither Moor nor Christian can prevail against it; if I could have it from my sister either for money or exchange, I should be Lord of Spain. Then the king returned to his tents, and sent for the Cid, and said unto him, Cid, you well know how manifoldly you are bound unto me. I have ever shown favour unto you, and you have ever served me as the loyalest vassal that ever did service to his lord. Now therefore I beseech you as my friend and true vassal, that you go to Zamora to my sister Donya Urraca, and say unto her again, that I beseech her to give me the town either for a price, or in exchange, and I will give to her Medina de Rioseco, with the whole Infantazgo, from Villalpando to Valladolid, and Tiedra also, which is a good Castle; and I will swear unto her, with twelve knights of my vassals, never to break this covenant between us; but if she refuseth to do this I will take away the town from her by force. And my Cid kissed the hand of the king and said unto him, This bidding, sir, should be for other messenger, for it is a heavy thing for me to deliver it; for I was brought up in Zamora by your father's command, with Donya Urraca and with his sons, and it is not fitting that I should be the bearer of such bidding. And the king persisted in requiring of him that he should go, insomuch that he was constrained to obey his will. And he took with him fifteen of his knights and rode towards Zamora, and when he drew nigh he called unto those who kept guard in the towers not to shoot their arrows at him, for he was Ruydiez of Bivar, who came to Donya Urraca with the bidding of her brother King Don Sancho. With that there came down a knight who had the keeping of the gate, and he bade the Cid enter. It pleased the Infanta well that he should be the messenger, and she bade him come before her that she might know what was his bidding.