It was fought primarily in Castile and its coastal waters between the local and allied forces of the reigning king, Peter, and his illegitimate brother Henry of Trastámara over the right to the crown.

His illegitimate brother Henry quickly obtained the support of not only the upper noblesse, but France, Aragon, and the Papacy.

He refused, however, to make good on his dealings with the English and his allies, including the Prince of Wales himself, soon left.

In 1368, Henry and Charles of France signed the Treaty of Toledo whereby the Castilians lent a fleet in the Bay of Biscay to the French in return for military aid on land.

He was acclaimed Henry II and immediately solidified his rule by removing Jews from high office.