and acknowledged her as the sole heir to the crown of Castille, her supporters had extracted concessions. Juan II died in 1479, and Ferdinand succeeded to the throne in January of that year.

In September 1479, Portugal and the Catholic Monarchs of Aragon and Castile resolved major issues between them through the Treaty of Alcáçovas, including the issue of Isabella's rights to the crown of Castile. Through close cooperation, the royal couple were successful in securing political