Alfonso X (1221-1284) was king of Castile and León from 1252 to 1284. Also known as Alfonso the Wise, he was one of the greatest royal patrons of learning of the Middle Ages.

The eldest son of Ferdinand III and Beatrice of Swabia, Alfonso was born in Toledo on Nov. 23, 1221. As a youth, he was tutored in the arts of war and governance. In 1247 he drove the Arabs from Murcia, and in 1248 he played an important role in his father's capture of Seville. The following year he married Violante, daughter of James I of Aragon, who bore him 10 children.

Alfonso became king in 1252 and immediately embarked upon bellicose adventures. He fought Alfonso III of Portugal over some frontier posts in the Algarve. In 1254 he invaded Gascony and soon after laid claim to the throne of Navarre, a move which earned him the hostility of his father-in-law, the King...