King of Castile and León (1252–84). His reign was a contrast between the failure of his political ambitions and his scholarly success as a law‐giver. He spent fruitless years trying to become Holy Roman Emperor and failed to complete his father’s Crusade against the Moors in southern Spain. His indecision caused his son, Sancho IV, to rebel and isolate him in Seville. Of real importance was his Siete Partidas (1256), a collection of constitutional, civil, and criminal law, the first such work to be written in Spanish.