MarriageAt the time of their marriage on October 19, 1469, Isabella was eighteen years old and the heiress presumptive to the , while Ferdinand was seventeen and heir apparent to the . They met for the first time in Valladolid in 1469 and married within a week. From the start, they had a close relationship and worked well together. Both knew that the crown of Castile was "the prize, and that they were both jointly gambling for it". However, it was a step toward the unification of the lands on the Iberian peninsula, which would eventually become Spain. They were second cousins, so in order to marry they needed a papal dispensation. Pope Paul II, an Italian pope opposed to Aragon's influence on the Mediterranean and to the rise of monarchies strong enough to challenge the Pope, refused to grant one, so they falsified a papal bull of their own. Even though the bull is known to be false, it is uncertain who was the material author of the falsification. Some experts point at Carrillo de Acuña, Archbishop of Toledo, and others point at Antonio Veneris. Pope Paul II would remain a bitter enemy of Spain and the monarchy for all his life, and is attributed the quote, "May all Spaniards be cursed by God, schismatics and heretics, the seed of Jews and Moors." Isabella's claims to it were not secure, since her marriage to Ferdinand enraged her half-brother Henry IV of Castile and he withdrew his support for her being his heiress presumptive that had been codified in the Treaty of the Bulls of Guisando. Henry instead recognised Joanna la Beltraneja, Joanna of Castile, born during his marriage to Joanna of Portugal, but whose paternity was in doubt, since Henry was rumored to be impotent. When Henry died in 1474, Isabella asserted her claim to the throne, which was contested by thirteen-year-old Joanna. Joanna sought aid of her husband (who was also her uncle), Afonso V of Portugal, to claim the throne. This dispute between rival claimants led to the War of the Castilian Succession, War of 1475–1479. Isabella called on the aid of Aragon, with her husband, the heir apparent, and his father, Juan II of Aragon providing it. Although Aragon provided support for Isabella's cause, Isabella's supporters had extracted concessions, Isabella was acknowledged as the sole heir to the crown of Castile. Juan II died in 1479, and Ferdinand succeeded to the throne in January 1479. In September 1479, Portugal and the Catholic Monarchs of Aragon and Castile resolved major issues between them through the Treaty of Alcáçovas, including the issue of Isabella's rights to the crown of Castile. Through close cooperation, the royal couple were successful in securing political power in the Iberian peninsula. Ferdinand's father had advised the couple that "neither was powerful without the other". Though their marriage united the two kingdoms, leading to the beginnings of modern Spain, they ruled independently and their kingdoms retained part of their own regional laws and governments for the next centuries.
Royal motto and emblemsThe coat of arms of the Catholic Monarchs was designed by Antonio de Nebrija with elements to show their cooperation and working in tandem. The royal motto they shared, ''Tanto monta, monta tanto, Isabel como Fernando, Tanto monta'' ("as much one as the other"), came to signify their cooperation."Liss, "Isabel and Fernando", p. 380. The motto was originally used by Ferdinand as an allusion to the Gordian knot: ''Tanto monta, monta tanto, cortar como desatar'' ("It's one and the same, cutting or untying"), but later adopted as an expression of equality of the monarchs: ''Tanto monta, monta tanto, Isabel como Fernando'' ("It's one and the same, Isabella the same as Ferdinand"). Their emblems or heraldic devices, seen at the bottom of the coat of arms, were a yoke and a sheaf of arrows. ''Y'' and ''F'' are the initials of Ysabel (spelling at the time) and Fernando. A double yoke is worn by a team of oxen, emphasizing the couple's cooperation. Isabella's emblem of arrows showed the armed power of the crown, "a warning to Castilians not acknowledging the reach of royal authority or that greatest of royal functions, the right to mete out justice" by force of violence. The iconography of the royal crest was widely reproduced and was found on various works of art. These badges were later used by the fascist Spanish political party Falange, which claimed to represent the inherited glory and the ideals of the Catholic Monarchs.
Royal CouncilsThe establishment of Polysynodial System, System of Royal Councils to oversee discrete regions or areas was Isabella succeeded to the throne of Castile in 1474 when Ferdinand was still heir-apparent to Aragon, and with Aragon's aid, Isabella's claim to the throne was secured. As Isabella's husband was king of Castile by his marriage and his father still ruled in Aragon, Ferdinand spent more time in Castile than Aragon at the beginning of their marriage. His pattern of residence Castile persisted even when he succeeded to the throne in 1479, and the absenteeism caused problems for Aragon. These were remedied to an extent by the creation of the Council of Aragon in 1494, joining the Council of Castile established in 1480. The Council of Castile was intended "to be the central governing body of Castile and the linch-pin of their governmental system" with wide powers and with royal officials who were loyal to them and excluded the old nobility from exercising power in it. The monarchs created the Holy Office of the Inquisition, Spanish Inquisition in 1478 to ensure that individuals converting to Christianity did not revert to their old faith or continue practicing it. The :es:Consejo y Comisaría de Cruzada, Council of the Crusade was created under their rule to administer funds from the sale of crusading bulls. In 1498 after Ferdinand had gained control of the revenues of the wealthy and powerful Spanish military orders, he created the :es:Consejo de las Órdenes, Council of Military Orders to oversee them. The conciliar model was extended beyond the rule of the Catholic Monarchs, with their grandson, Charles V, Holy Roman Emperor establishing the Council of the Indies, the :es:Consejo de Hacienda, Council of Finance, and the :es:Consejo de Estado (España), Council of State.
Domestic policyThe Catholic Monarchs set out to restore royal authority in Spain. To accomplish their goal, they first created a group named the Hermandad, Holy Brotherhood. These men were used as a judicial police force for Castile, as well as to attempt to keep Castilian nobles in check. To establish a more uniform Judiciary, judicial system, the Catholic Monarchs created the Royal Council, and appointed magistrates (judges) to run the towns and cities. This establishment of royal authority is known as the Pacification of Castile, and can be seen as one of the crucial steps toward the creation of one of Europe's first strong nation-states. Isabella also sought various ways to diminish the influence of the ''Cortes Generales'' in Castile, though Ferdinand was too thoroughly Aragonese people, Aragonese to do anything of the sort with the equivalent systems in the Crown of Aragon. Even after his death and the union of the crowns under one monarch, the Aragonese, Catalan, and Valencian ''Corts'' (parliaments) retained significant power in their respective regions. Further, the monarchs continued ruling through a form of medieval contractualism, which made their rule pre-modern in a few ways. One of those is that they traveled from town to town throughout the kingdom in order to promote loyalty, rather than possessing any single administrative center. Another is that each community and region was connected to them via loyalty to the crown, rather than bureaucratic ties.
Religious policyFile:Capitulação de Granada - Vicente Barneto y Vazquez.png, upleft, Capitulation of Granada 1492. Painting of the 1900s. Along with the desire of the Catholic Monarchs to extend their dominion to all the kingdoms of the Iberian Peninsula, their reign was characterised by religious unification of the peninsula through militant Catholicism. Petitioning the pope for authority, Pope Sixtus IV issued a bull in 1478 to establish a Holy Office of the Inquisition in Castile. This was to ensure that Jews and Muslims who converted to Christianity did not revert to their previous faiths. The papal bull gave the sovereigns full powers to name inquisitors, but the papacy retained the right to formally appoint the royal nominees. The inquisition did not have jurisdiction over Jews and Muslims who did not convert. Since in the kingdom of Aragon it had existed since 1248, the Spanish Inquisition was the only common institution for the two kingdoms. Pope Innocent VIII confirmed Dominican Tomás de Torquemada, a confessor of Isabella, as Grand Inquisitor of Spain, following in the tradition in Aragon of Dominican inquisitors. Torquemada pursued aggressive policies toward converted Jews (conversos) and moriscos. The pope also granted the Catholic Kings the right of Patronato real, patronage over the ecclesiastical establishment in Granada and the Canary Islands, which meant the control of the state in religious affairs. The monarchs began a series of campaigns known as the Granada War (1482–1492), which was aided by Pope Sixtus IV's granting the tithe revenue and implementing a crusade tax so that the monarchs could finance the war. After 10 years of fighting the Granada War ended in 1492 when Emir Muhammad XII of Granada, Boabdil surrendered the keys of the Alhambra Palace in Granada to the Castilian soldiers. With the fall of Granada in January 1492, Isabella and Ferdinand pursued further policies of religious unification of their realms, in particular the expulsion of Jews who refused to convert to Christianity. After a number of revolts, Ferdinand and Isabella ordered the Alhambra Decree, expulsion of all Jews from Spain. People who converted to Catholicism were not subject to expulsion, but between 1480 and 1492 hundreds of those who had converted (''conversos'' and ''moriscos'') were accused of secretly practicing their original religion (crypto-Judaism or crypto-Islam) and arrested, imprisoned, interrogated under torture, and in some cases burned to death, in both Castile and Aragon. The Inquisition had been created in the twelfth century by Pope Lucius III to fight heresy in the south of what is now France and was constituted in a number of European kingdoms. The Catholic Monarchs decided to introduce the Inquisition to Castile, and requested the Pope's assent. On 1 November 1478, Pope Sixtus IV published the papal bull ''Exigit Sinceras Devotionis Affectus'', by which the Inquisition was established in the Kingdom of Castile; it was later extended to all of Spain. The bull gave the monarchs exclusive authority to name the inquisitors. During the reign of the Catholic Monarchs and long afterwards the Inquisition was active in prosecuting people for violations of Catholic orthodoxy such as crypto-Judaism, heresy, Protestantism, blasphemy, and bigamy. The last trial for crypto-Judaism was held in 1818. In 1492 the monarchs issued a decree of expulsion of Jews, known formally as the Alhambra Decree, which gave Jews in Spain four months to either convert to Catholicism or leave Spain. Tens of thousands of Jews emigrated to other lands such as Portugal, North Africa, the Low Countries, Italy and the Ottoman Empire.
Foreign policyAlthough the Catholic Monarchs pursued a partnership in many matters, because of the histories of their respective kingdoms, they did not always have unified viewpoint in foreign policy. Despite that, they did have a successful expansionist foreign policy due to a number of factors. The victory over the Muslims in Granada allowed Ferdinand to involve himself in policy outside the Iberian peninsula. The diplomatic initiative of King Ferdinand continued the traditional policy of the Crown of Aragon, with its interests set in the Mediterranean, with interests in Italy and sought conquests in North Africa. Aragon had a traditional rivalry with France, which had been traditional allies with Castile. Castile's foreign interests were focused on the Atlantic, making Castile's funding of the voyage of Columbus an extension of existing interests. Castile had traditionally had good relations with the neighboring Kingdom of Portugal, and after the Portuguese lost the War of the Castilian Succession, Castile and Portugal concluded the Treaty of Alcáçovas. The treaty set boundaries for overseas expansion which were at the time disadvantageous to Castile, but the treaty resolved any further Portuguese claims on the crown of Castile. Portugal did not take advantage of Castile's and Aragon's focus on the reconquest of Granada. Following the reestablishment of good relations, the Catholic Monarchs made two strategic marriages to Portuguese royalty. The matrimonial policy of the monarchs sought advantageous marriages for their five children, forging royal alliances for the long term benefit of Spain. Their first-born, a daughter named Isabella of Asturias, Isabella, married Afonso, Prince of Portugal, Afonso of Portugal, forging important ties between these two neighboring kingdoms that would lead to enduring peace and future alliance. Joanna of Castille, Joanna, their second daughter, married Philip I of Castile, Philip the Handsome, the son of Holy Roman Emperor Maximilian I, Holy Roman Emperor, Maximilian I. This ensured alliance with the Holy Roman Empire, a powerful, far-reaching European territory which assured Spain's future political security. Their only son, John, Prince of Asturias, John, married Margaret of Austria, Duchess of Savoy, Margaret of Austria, seeking to maintain ties with the Habsburg dynasty, on which Spain relied heavily. Their fourth child, Maria of Aragon (1482-1517), Maria, married Manuel I of Portugal, strengthening the link forged by Isabella's elder sister's marriage. Their fifth child, Catherine of Aragon, Catherine, married Arthur, Prince of Wales and heir to the throne of England, in 1501; he died at the age of 15 a few months later, and she married his younger brother shortly after he became King Henry VIII of England in 1509. These alliances were not all long lasting, with their only son and heir-apparent John dying young; Catherine was divorced by Henry VIII; and Joanna's husband Philip dying young, with the widowed Joanna deemed mentally unfit to rule. Under the Catholic Monarchs an efficient army loyal to the Crown was created, commanded by Castilian Gonzalo Fernández de Córdoba, known as the '' Great Captain ''. Fernández de Córdoba reorganised the military troops on a new combat unit, Tercio , tercios reales, which entailed the creation of the first modern army dependent on the crown, regardless of pretensions of the nobles.
Voyages of ColumbusThrough the Capitulations of Santa Fe, Genoese mariner Christopher Columbus received finances and was authorised to sail west and claim lands for Spain. The monarchs accorded him the title of Admiral of the Ocean Sea and he was given broad privileges. His voyage west resulted in the European colonization of the New World, Americas and brought the knowledge of its existence to Europe. Columbus' first expedition to the supposed Indies actually landed in the Bahamas on October 12, 1492. Since Queen Isabella had provided the funding and authorization for the voyage, the benefits accrued to the Kingdom of Castile. "Although the subjects of the Crown of Aragon played some part in the discovery and colonization of the New World, the Indies were formally annexed not to Spain but to the Crown of Castile."John Huxtable Elliott, Elliott, J.H. ''Imperial Spain 1479–1716''. New York: New American Library 1963. He landed on the island of Guanahani, and called it San Salvador. He continued onto Cuba, naming it Juana, and finished his journey on the island of the Dominican Republic and Haiti, calling it Hispaniola, or ''La Isla Española'' ("the Spanish [Island]" in Castilian). On his second trip, begun in 1493, he found more Caribbean islands including Puerto Rico. His main goal was to colonize the existing discoveries with the 1500 men that he had brought the second time around. Columbus finished his last expedition in 1498, and discovered Trinidad and the coast of present-day Venezuela. The colonies Columbus established, and conquests in the Americas in later decades, generated an influx of wealth into the new unified state of , leading it to be the major power of Europe from the end of the sixteenth century until the mid-seventeenth century, and the largest empire until 1810.
DeathIsabella's death in 1504 ended the remarkably successful political partnership and personal relationship of their marriage. Ferdinand remarried Germaine of Foix in 1505, but they produced no living heir. Had there been one, Aragon would doubtless have been separated from Castile. The Catholic Monarchs' daughter Joanna succeeded to the crown of Castile, but was deemed unfit to rule and following the death of her husband Phillip the Fair, Ferdinand retained power in Castile as regent until his death. He died in 1516 and is buried alongside his first wife Isabella in Granada, the scene of their great triumph in 1492. Joanna's son Charles V, Holy Roman Emperor, Charles I of Spain (also Charles V, Holy Roman Emperor) came to Spain, and until his mother's death she was nominal co-ruler of both Castile and Aragon. With her death, Charles succeeded to the territories that his grandparents had accumulated and brought the Habsburg territories in Europe to the expanding Spanish Empire.