King Henry IV of Castile died Death in December 1474 , setting off the War Hostile_encounter of the Castilian Succession between Henry 's daughter Joanna la Beltraneja and Henry 's half-sister Isabella .

The war Hostile_encounter raged from 1475–1479 , setting Placing Isabella 's supporters Supporting and the Crown of Aragon against Joanna 's supporters Supporting , Portugal , and France .

Isabella 's daughter Joanna succeeded to the throne .

Due to Joanna 's mental instability , Castile was ruled Control by the nobles and her father , King Ferdinand II of Aragon , as a regent .

After Ferdinand 's death Death in 1516 , Joanna 's sixteen-year-old son Charles was proclaimed Statement king of both Castile and Aragon .

The rebels chose Choosing Charles ' own mother , Queen Joanna , as an alternative ruler , hoping they could control Control her madness .