Fill in the Blanks CATHOLIC MONARCHSOnline version Some facts about the beginning of Catholic Monarchs government. by Alfonso Poza 1 unification niece War throne week 1469 Treaty Aragon Castile died Monarchs The Catholic Monarchs married on October 19 , , in the city of Valladolid . Isabella was 18 years old and Ferdinand a year younger . At the time of their , Isabella was the heir to the Crown of , while Ferdinand was heir to the Crown of . They met for the first time in Valladolid in 1469 and married within a . It was a step toward the of the Iberian peninsula , which would eventually become Spain . When her brother Henry IV of Castile in 1474 , Isabella claimed the throne , which was contested by her thirteen - year - old Joanna , Henry ? s daughter . Joanna was aided by her husband ( who was also her uncle ) , Alfonso V of Portugal , to claim the . This dispute between rival claimants , niece and aunt , led to the of 1475 ? 1479 . Isabella called on the aid of Aragon , with her husband and his father , Juan II of Aragon providing it . In September 1479 , Portugal and the Catholic of Aragon and Castile signed a peace treaty called the of Alcáçovas , ending war . Isabella began her rule as Queen of Castile .
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