War of the Castilian Succession
Fernando II took part in the War of the Castilian Succession. Following King Henry IV of Castile's death, the King's daughter and heir, Joanna La Beltraneja, married to King Afonso V, was proclaimed "Queen of Castile", but she had the opposition of her half-aunt (the future queen Isabella I of Castile) to contend with. The Portuguese invaded Castile, and during the Battle of Toro, Fernando was responsible for Queen Joanna’s safety.