Isabella of Castile (1451–1504)

Queen of Castile whose marriage to Ferdinand of Aragon was the foundation of a united Spanish kingdom. Born in Madrigal, in the kingdom of Castile, she was the daughter of King John II of Castile and Queen Isabella of Portugal. In 1454, her half brother Henry IV became the Castilian king. When Henry sought to deny the succession to his brother, Afonso, supporters of Afonso rebelled, fighting with Henry's army at the Battle of Olmedo in 1467. In the next year, Afonso died, and the rebels then supported Isabella as their candidate for the throne. In 1469, Isabella married Ferdinand, prince of the kingdom of Aragon. Henry conferred the succession on his daughter Juana, a candidate supported by the monarch of Afonso V of Portugal.

In 1474, on the death of Henry IV, Isabella was crowned Queen of Castile, but she was challenged by Afonso and Joan. Ferdinand's army defeated the Portuguese at the Battle of Toro in 1476, after which Afonso gave up his opposition to Isabella. Three years later, Ferdinand became the king of Aragon. Ferdinand and Isabella united the courts of Castile and Aragon. A new parliament, the Cortes, began meeting, and a new system of laws and administration laid the groundwork for a united kingdom of Spain.

Determined to establish her legitimacy as queen, which had been so forcefully challenged, Isabella set out to enlarge and enhance the kingdom and her own authority. She led the campaign to recapture the kingdom of Granada, the last vestige of Moorish control of the Iberian Peninsula. Over ten years, the Spanish armies laid siege to a series of fortified towns while the Moors laid waste to the countryside. This campaign ended with final victory at Granada in 1492, ending the centuries-long campaign against the Moors known as the Reconquista.

In the meantime, Isabella had been rejecting the request of an Italian navigator, Christopher Columbus, to support a voyage of discovery to the west, where Columbus believed he would find an easy route to the spices and other riches of the East Indies. Such a route, Columbus promised, would allow Spain to bypass the Indian Ocean, which was under the control of the Portuguese, and build its own trading empire in Asia. In August 1492, she finally gave in, and Columbus's voyage to the New World that fall began Spain's conquest of colonies in the Western Hemisphere. The rivalry between Spain and Portugal was partially resolved by the Treaty of Tordesillas in 1494, by which the two nations divided the world into two spheres of colonization.

At home, Isabella was transforming Spain into a purely Christian state. Ferdinand and Isabella had established the Inquisition in 1478 to investigate charges of false conversion and heresy. The 1492 Decree of Alhambra called for all Jews to either convert to Christianity or leave the kingdom. In 1502, after a revolt, Muslims were subject to forced baptism or exile. Isabella also vigorously pursued a policy of strengthening Spain's ties to other European realms through marriage. She allied Spain with the Habsburg monarchy by arranging the marriage of her son Juan and daughter Joanna into the Habsburg dynasty. She also engaged her daughter Isabel to the king of Portugal, Manuel, and after the death of Isabel engaged her second daughter Maria to the same king. Her grandson Charles became king of Spain as Charles I and Holy Roman Emperor as Charles V. Her astute marital diplomacy raised Spain's importance in European affairs, while her sponsorship of Columbus established a realm of overseas colonies that would enrich the Spanish treasury for the next two centuries.

See Also: Charles V; Columbus, Christopher; Ferdinand II of Aragon; Inquisition