To Isabella and Ferdinand, one of the most renowned royal couples in history, their primary achievement was not funding conquistadors to expand their empire overseas or uniting disparate kingdoms into what eventually became modern Spain. The couple believed their most important legacy was ridding Spain of the Muslims.
When Isabella, the daughter of King John II of Castile, and Ferdinand, the son of King John I of Aragon, were married in October 1469, Muslims had ruled large parts of the Iberian Peninsula for more than 700 years. Propelled by their Christian faith to pursue an expensive, bloody, 10-year battle to unite their land under Christian leadership, the couple finally conquered the last Muslim stronghold in January 1492.
With peace assured at home, Ferdinand and Isabella quickly agreed to sponsor an expedition across the Atlantic Ocean to be led by a sea captain named Christopher Columbus. This voyage of discovery was not first time Isabella showed an interest in strengthening Spain's commercial prospects overseas. Fifteen years earlier, she made her initial attempt to challenge Portugal's dominance at sea by claiming Spain's first overseas territories, the three largest Canary Islands. She sent several expeditions to conquer the indigenous Canarians, who managed to hold out until 1496. Although she forbade the vanquished people to be sold as slaves, her orders were ignored, foreshadowing later events in the New World.
When Columbus returned to Spain in 1493 after visiting several islands in the Caribbean, the Spanish age of discovery in the Americas was underway. Between 1500 and 1502 alone, the Crown authorized twelve new expeditions to the region including Columbus' fourth and final voyage.
In Europe, to bolster their forces against their primary enemy, France, Ferdinand and Isabella signed treaties with England, Holy Roman Emperor Maximilian I, and the Hapsburg family. They set the course for Spain's great rise in the coming decades by marrying two of their four children off to the Hapsburgs, who ruled much of central Europe. Their daughter, Catherine of Aragon, became the first wife of England's future king, Henry VIII.
Isabella died in 1504, and the following year Ferdinand remarried. He had spent much of the previous decade fighting the French in Italy, where he showed great diplomatic prowess by founding the Holy League, an alliance of Italian states that included the pope. The League repeatedly drove the French out of Italy, allowing Spain to maintain control of Naples and Sicily. In his final conquest, Ferdinand invaded Navarre, in the northeast region of the Iberian Peninsula, and brought it under his rule.
For three decades, Isabella and Ferdinand ruled most of the land that makes up modern day Spain, uniting the kingdoms of Castile and Aragon through their marriage and expanding their territory into previously unknown continents. Although they did not completely unify Spain, by the time of their deaths the country was on its way to becoming the most powerful in Europe.