War of the Castilian Succession
In the War of the Castilian Succession, Diego and his father supported Juana la Beltraneja, who lost the battle for the throne. Diego, who had become 2nd Duke of Escalona after the death of his father in October 1474, was pardoned by Isabella I of Castile and allowed to keep his properties. But he wasn't chosen as successor for his father as Grand Master of the Order of Santiago.