Facts and Events
Born at Zamora, Sancho was the eldest son of Ferdinand I of Castile and Sancha of León, the eventual heiress to the Leonese crown. He was married to Alberta, a possible daughter of William I, king of England. He succeeded in Castile while his younger brother Alfonso succeeded in their mother's inheritance of León and Galicia was given to the youngest son García.
In 1068, Sancho defeated his cousins Sancho IV of Navarre and Sancho of Aragon in the War of the Three Sanchos. He reconquered Bureba, Alta Rioja, and Álava, which his father had given to Sancho of Navarre's father, García, in return for aid against Bermudo III of León. In that year, he defeated Alfonso, his brother, at Llantada, but he soon teamed up with him to conquer Galicia. They succeeded (1071) and partitioned it, but Sancho then turned on Alfonso. With the aid of his alférez El Cid, he defeated Alfonso at Golpejera (1072). He then forced him into exile in Toledo and took over León as king, being crowned in the city of León on 12 January 1072.
Some Leonese resistance still persisted, and his sister, Urraca, Lady of Zamora, held that city against his rule. He had surrounded the city and begun a siege, when a Zamoran noble, named Vellido Dolfos, assassinated Sancho on 6 October 1072. Vellido had gained entry to Sancho's camp pretending to be a deserter, and sought a private conference with Sancho to tell him the weakness of the Zamoran defence. Once before Sancho, however, he used the king's own sword to impale him in the back. Fleeing, he was chased back to Zamora by El Cid but escaped into the town through a gateway since called Portillo del Traidor ("gateway of the traitor"). Sancho was succeeded in his kingdoms by the brother he had previously deposed, Alfonso. He was buried in San Salvador de Oña.