Alfonso X was King of Castile, León and Galicia from 30 May 1252 until his death in 1284. During the election of 1257, a dissident faction chose him to be king of Germany on 1 April. He renounced his claim to Germany in 1275, and in creating an alliance with the Kingdom of England in 1254, his claim on the Duchy of Gascony as well

The Kingdom of León was an independent kingdom situated in the northwest region of the Iberian Peninsula. It was founded in 910 when the Christian princes of Asturias along the northern coast of the peninsula shifted their capital from Oviedo to the city of León. The kings of León fought civil wars, wars against neighbouring kingdoms, and campaigns to repel invasions by both the Moors and the Vikings, all in order to protect their kingdom's changing fortunes.