The Reconquista

Conclusion of the Reconquista and start of the Spanish Inquisition
The monarchs oversaw the final stages of the Reconquista of Iberian territory from the Moors with the conquest of Granada, conquered the Canary Islands, and expelled the Jews from Spain under the Alhambra Decree. Although until the 13th century religious minorities (Jews and Muslims) had enjoyed considerable tolerance in Castile and Aragon – the only Christian kingdoms where Jews were not restricted from any professional occupation – the situation of the Jews collapsed over the 14th century, reaching a climax in 1391 with large scale massacres in every major city except Ávila.

Over the next century, half of the estimated 80,000 Spanish Jews converted to Christianity (becoming "conversos"). The final step was taken by the Catholic Monarchs, who, in 1492, ordered the remaining Jews to convert or face expulsion from Spain. Depending on different sources, the number of Jews actually expelled, traditionally estimated at 120,000 people, is now believed to have numbered about 40,000.

Over the following decades, Muslims faced the same fate; and about 60 years after the Jews, they were also compelled to convert ("Moriscos") or be expelled. However, sufficient numbers of Moriscos stayed that Muslim culture remained influential in Spain. Jews and Muslims were not the only people to be persecuted during this time period. All Roma (Gitano, Gypsy) males between the ages of 18 and 26 were forced to serve in galleys – which was equivalent to a death sentence – but the majority managed to hide and avoid arrest.

Isabella and Ferdinand authorized the 1492 expedition of Christopher Columbus, who became the first known European to reach the New Worldsince Leif Ericson. This and subsequent expeditions led to an influx of wealth into Spain, supplementing income from within Castile for the state that would prove to be a dominant power of Europe for the next two centuries.

Isabella ensured long-term political stability in Spain by arranging strategic marriages for each of her five children. Her firstborn, a daughter named Isabella, married Afonso of Portugal, forging important ties between these two neighboring countries and hopefully ensuring future alliance, but Isabella soon died before giving birth to an heir. Juana, Isabella's second daughter, married into the Habsburg dynasty when she wed Philip the Fair, the son of Maximilian I, King of Bohemia (Austria) and likely heir to the crown of the Holy Roman Emperor.

This ensured an alliance with the Habsburgs and the Holy Roman Empire, a powerful, far-reaching territory that assured Spain's future political security. Isabella's only son, Juan, married Margaret of Austria, further strengthening ties with the Habsburg dynasty. Isabella's fourth child, Maria, married Manuel I of Portugal, strengthening the link forged by her older sister's marriage. Her fifth child, Catherine, married King Henry VIII of England and was mother to Queen Mary I of England.