Overview
The term “Catholic Kings” — Los Reyes Católicos — refers to the joint sovereigns Ferdinand and Isabel, whose determined policies united Spain, completed the Reconquista and propelled a once-peripheral kingdom into a major world power.
Throughout the Middle Ages, the Christian kingdoms of the Iberian Peninsula fought to reclaim territory conquered by Muslim powers since the 8th century. Although significant advances were made in the 13th century under Ferdinand III of Castile and Jaime I of Aragon, by the late 14th century the Christian states — Castile, Aragon, Portugal and Navarre — remained politically and culturally distinct. Rivalries and disunity slowed the Reconquista to a halt.
By the mid-15th century Castile, the key Christian kingdom, was weakened by poor governance and civil war. Doubts about the legitimacy of King Henry IV’s daughter led to the succession passing to his sister Isabel. Her marriage in 1469 to her cousin Ferdinand, heir to the Aragonese throne, created a powerful political union between the peninsula’s two strongest Christian states. Isabel was proclaimed queen in Segovia in 1474.
This marriage shaped the future of Spain. It provided both Mediterranean and Iberian orientation, joined Castile’s population and resources with Aragon’s commercial and political strengths, and set both kingdoms on a unified course that would revive the Reconquista. Their personal commitment to ruling jointly — expressed in their motto Tanto monta, monta tanto — created the conditions for a recognisably modern Spanish state to emerge.
The achievements of the Catholic Kings include:
- Completion of the Reconquista
- Establishment of a strong, centralised Spanish monarchy
- Expansion of Spanish power in Europe — especially in Italy
- Sponsorship of Columbus’s voyages
- Identification of national unity with the Catholic faith — leading Pope Alexander VI to grant them the title “Catholic Kings” in 1494
Civil War and Reconquest
The Castilian-Aragonese union initially faced opposition, particularly from southern supporters of the Portuguese claim. Ferdinand’s military skill prevailed, and Portugal was defeated at Toro in 1476. Thereafter, Ferdinand and Isabel devoted their full attention to the Reconquista.
Beginning in 1482, they waged a long war of attrition against the Nasrid kingdom of Granada. Avoiding grand cavalry battles, Castilian infantry — largely hardy peasants — captured territory piece by piece. Internal conflict weakened Granada, and the fall of Málaga in 1487 sealed its fate. After extended negotiations, Granada’s ruler Boabdil surrendered the city on 2 January 1492.
The New Spain
With the last Muslim stronghold removed, Spain was unified. Only Portugal and France remained as land frontiers. A new governmental structure was needed, as each former kingdom had long maintained its own medieval laws and traditions. Castile had been a feudal monarchy dominated by powerful nobles, whereas Aragon’s monarchy was contractually bound to representative institutions (corts).
The Catholic Kings strengthened royal authority by ensuring that titles, offices and municipal charters could only be granted by the Crown; justice was administered solely through royal courts (audiencias); and taxes were collected by royal agents, making revenue independent of the cortes. A rural police force (La Hermandad) was revived, though its role was largely symbolic.
The most significant innovation was the creation of the corregidor after 1500 — a royal official who combined administrative, judicial and supervisory powers at the local level. Although implementation varied regionally, this reshaped relations between state and community and became the backbone of Spanish administration until the 19th century. Enforcing this system would later spark revolts, including the Castilian uprising of 1520 and the Catalan revolt of 1640.
Spanish Expansion
The union brought with it Aragon’s Mediterranean possessions: Sicily, Naples and Sardinia. When France seized Naples in 1495, Spain intervened. Under the brilliant general Gonzalo de Córdoba — “El Gran Capitán” — Spain defeated the French and by 1504 controlled Italy south of Rome. His innovations, including the tercio formation, made Spanish infantry the most formidable in Europe.
Even more consequential was expansion into the New World following Columbus’s voyages. Although initially hesitant, the Catholic Kings — particularly Isabel — embraced his plan once Granada had fallen, seeing it as a continuation of Christian mission. Expeditions to the Americas were joint ventures of the Crown and private enterprise. Officially, all new lands fell to Castile.
At Isabel’s death in 1504, neither she nor Columbus fully understood the scale of the new continents or the civilisations they contained. Nonetheless, without their early support, Spain’s vast American empire would not have emerged.
The Religious Question
The fall of Granada raised pressing religious issues. A unified Spain, in the mindset of the time, required a unified faith. Initially, the Moors of Granada were treated leniently under the terms of surrender, and early clerics were impressed by Islamic charitable traditions. But in 1499 Cardinal Cisneros instituted forced conversions, sparking revolt. After its suppression, Muslims were given a stark choice: conversion or exile. Many departed for North Africa, though isolated communities preserved some customs for generations.
The Jews of Spain, present since Roman times and influential in commerce, scholarship and diplomacy, faced an even harsher fate. Although long tolerated by both Muslim and Christian rulers, they became targets of resentment — from nobles who opposed Jewish influence and from common people who associated Jews with usury or occult practices. Anti-Jewish riots had erupted in 1391 and 1446.
The establishment of the Inquisition in 1478 signalled a new era of religious scrutiny. In 1492, amid increasing hostility, the Edict of Expulsion was issued. More than three-quarters of Spain’s 200,000 Jews left, taking with them skills and intellectual traditions whose loss later generations deeply regretted. Modern historians have even speculated on Jewish origins for figures such as Columbus and Cervantes.
Legacy
Ferdinand and Isabel rank among Europe’s most influential rulers. Their consolidation of the Spanish state, completion of the Reconquista, sponsorship of transatlantic exploration and expansion of power in Europe forged Spain into the first great modern empire.
Yet their zeal in religious and racial policy sowed seeds of intolerance that would echo through Spanish history, contributing to later periods of conflict and repression.