79: Iberia at the Crossroads: Political Crisis in the 15th Century

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Alfonso de Palencia, Chronicles of Enrique IV, late 15th century
“Immediately Don Enrique, in the presence of all the aforementioned magnates, swore in the Legate's hands that the legitimate succession to the throne belonged to his sister Doña Isabel, princess and true heiress of the kingdoms of León and Castile and of all the other States that are enumerated as corresponding to the crown, notwithstanding what was previously agreed in favor of Doña Juana, daughter of the Queen, with solemn oath given by the Grandes and by the people, according to the custom of Spain.”


At the dawn of the fifteenth century, the Iberian Peninsula looked more like a complex political mosaic than the unified Spain we recognize today. Four major Christian kingdoms—Castile, Aragon, Portugal, and Navarre—shared the peninsula with the Muslim emirate of Granada, each pursuing its own ambitions and fiercely guarding its independence. The legacy of the centuries-long effort to reclaim Iberian lands from Muslim rule profoundly shaped these societies, resulting in militarized nobility and political structures designed for ongoing warfare rather than peaceful governance.

The century saw extraordinary changes: weak kings battling powerful nobles, constitutional crises that reshaped royal authority, and dynastic accidents that shifted the course of European history. By 1468, these seemingly chaotic events had created the conditions for the union of Castile and Aragon.

Throughout this narrative, I will use names in their original linguistic forms when appropriate—Catalan figures appear as Pere, Martí, and Jaume (Zhow-muh), while Castilian figures use Juan, Enrique, and Fernando—reflecting the rich linguistic diversity of medieval Iberia.

When Juan II inherited the Castilian throne in 1406 at age two, his uncle Fernando de Antequera served as regent until his rise to the Aragonese throne in 1412. Fernando's three sons, the Infantes (een-faan-tays) de Aragón, controlled such large territories within Castile that they could challenge royal authority itself. These princes represented what chroniclers called "the epicenter of Castilian instability”; their brotherhood bonds often proved stronger than loyalty to any crown.

For thirty years, the kingdom's fate largely depended on Álvaro de Luna, Juan II's controversial constable. Rising from humble Aragonese beginnings, he became one of the most powerful royal favorites. His enemies spread rumors that he had bewitched the king, preventing Juan from seeing anyone without Luna's permission. More seriously, they accused him of reducing the monarch to a figurehead: "Juan had no other task except to eat."

 Luna's policies anticipated those of the later Catholic Monarchs, Isabel and Ferdinand. He promoted capable lawyers over noble birth, strengthened the system of corregidores(kor-reh-hee-DOR-es) (royal judges), and aimed to centralize royal authority. His most significant victory came at the Battle of Olmedo in 1445, where royal forces decisively defeated the Infantes de Aragón, effectively ending their challenge to Castilian independence. Yet Luna's success bred jealousy among other nobles, and his increasingly tyrannical behavior—including arbitrary imprisonments and executions—created powerful enemies.

The constable's fall was as dramatic as his rise. Queen Isabel, Juan's second wife, developed a deadly hatred for the man who controlled her husband's every move. When Luna murdered the royal treasurer in Burgos Cathedral on Good Friday 1453, the symbolism was too powerful to ignore. Within weeks, the king who had relied on Luna for thirty years ordered his arrest and execution. Juan II died just one year later, leaving his heir Enrique IV to deal with the legacy of royal weakness and noble resurgence.

Enrique IV inherited a kingdom that seemed ready for recovery. The Infantes de Aragón were defeated, royal authority appeared restored, and the new king initially had broad support. Unlike his father, he was physically imposing and personally brave, leading successful campaigns against the emirate of Granada, the last Muslim stronghold on the Iberian peninsula. His first decade saw what contemporaries called "great obedience" from nobles and effective royal justice.

Yet Enrique's character had fatal flaws for a fifteenth-century monarch. His mercy, while admirable, was seen as a weakness. His informality and dislike of ceremony confused contemporaries who expected royal dignity. Most damaging, his alleged impotence became a source of public scandal and political manipulation. His first marriage to Blanche of Navarre was annulled in 1453 after thirteen childless years, with official documents citing witchcraft as the cause of his condition.

The king's second marriage to Joanna of Portugal in 1455 was intended to restore royal prestige through a Portuguese alliance. Instead, it led to new problems. Queen Joanna, young and lively, scandalized the Castilian court with her informality and rumored love affairs. When she gave birth to Princess Joanna in 1462, rumors quickly spread that the true father was Beltrán de la Cueva, the king's favored courtier. The princess became known as "la Beltraneja"—Beltrán's daughter—a nickname that would follow her for life.

Enrique's foreign policy was just as disastrous. When Catalans rebelled against Joan II of Aragon in 1462, they pledged loyalty to Castile, creating an unprecedented chance to control the peninsula. Enrique agreed, calling himself Count of Barcelona. However, his intervention fell apart when Louis XI of France ruled against Castilian interests, forcing Enrique to abandon the Catalans in exchange for worthless promises—showing his weakness to enemies both at home and abroad.


While Castile struggled with royal weakness and noble rebellion, the Crown of Aragon faced an even more serious crisis: the extinction of its native dynasty. Joan I, who reigned from 1387 to 1396, embodied both the cultural achievements and political failures of late medieval Catalonia. Known as "the Hunter," he supported literature and learning but neglected governance, preferring the hunt over the council chamber. 

Joan's biggest weakness was his vulnerability to foreign influence, primarily through his French wife, Yolande. Critics argued that "he had a French wife and was entirely French," pursuing policies that favored France over his own lands. When Joan died suddenly in 1396 while hunting, many saw his death without sacraments as divine punishment.

His brother Martí I presented a striking contrast. Known as "the Humane," this contemplative scholar pursued policies that restored much of Crown prestige, including the conquest of Sicily through joint efforts with his son Martí the Younger. Yet when both Martí the Younger and then Martí I died in 1410, his alleged deathbed words—"whoever justice should decide"—created a legal ambiguity.

The succession crisis exposed fundamental weaknesses in the Crown of Aragon's federal structure. Unlike unified kingdoms like France or England, the Crown was made up of separate territories—Catalonia, Aragon, Valencia, and the Mediterranean islands—each with its own laws, institutions, and interests. Martí's death without apparent heirs showed how this diversity could lead to paralysis when decisive action was needed.

Multiple candidates emerged: Jaume, Count of Urgel, had the strongest male-line descent; Louis of Anjou claimed inheritance through Joan I's daughter; Fernando de Antequera advanced his claim through Pere III's daughter.

Initially, Jaume seemed headed for victory with strong Catalan support. The turning point occurred when his supporter assassinated the Archbishop of Saragossa in June 1411, justifying Castilian military intervention. Soon after, three thousand Castilian troops took control of Aragon and Valencia. As one contemporary noted, Fernando earned the crown "with our laws, our money and our men."

The actual decision was made by nine compromisarios (arbitrators) meeting at Caspe from March to June 1412. The makeup of this panel nearly guaranteed Fernando's victory: three Aragonese judges were known supporters of the Castilian candidate, while the three Valencian members included the influential Dominican preacher Vicent Ferrer, a close ally of Pope Benedict XIII, who strongly backed Fernando. On June 24, six compromisarios voted for Fernando as "the nearest legitimate male relation of King Martí."

The Compromiso marked a decisive turning point. A Castilian prince now ruled the Crown of Aragon, bringing foreign interests and constitutional conflicts. As one historian observed, Fernando "never ceased to be a Castilian," viewing his new territories as opportunities to strengthen his family rather than kingdoms needing careful governance.


Fernando died in 1416 after just four years of rule, leading his son, the Infante Alfonso, to ascend the throne at age twenty. Alfonso V earned the nickname "el Magnánimo" for his conquest of Naples and support of Renaissance humanism. Still, his reign showed increasing tensions between Mediterranean imperial goals and Iberian political realities. 

Alfonso's character was shaped by dreams of glory and power. His longing for fame led him to commission bronze sculptures by Donatello, marble triumphal arches, and medals that celebrated his achievements. The inscription on his Neapolitan arch, calling him "Siculus, Italicus," showed his hope to be remembered as an Italian Renaissance prince rather than just an Iberian king. The conquest of Naples took twenty years and a lot of resources, finally ending in 1443 after continuous warfare.

From 1432 until he died in 1458, Alfonso lived permanently in Italy, ruling his Iberian kingdoms through regents. His absence created dangerous power vacuums that worsened internal conflicts. 

In Catalonia, social tensions escalated into open conflict between the Biga and Busca factions in Barcelona. The Biga, representing the established patricians, controlled the municipal government through traditional oligarchic networks. The Busca, made up of merchants, artisans, and workers, demanded political representation and economic reforms. Alfonso supported the Busca in hopes of gaining control of Barcelona.

The countryside experienced its own upheavals through the remensa issue. These peasants, tied to the land in a form of serfdom, organized to demand freedom from the malos usos (evil customs) that kept them subjugated. Alfonso alternately supported and abandoned the remensas as political circumstances changed, using their grievances as leverage against noble opponents while never providing consistent leadership for reform.

When Alfonso’s brother, Juan II (or Joan II in Catalan), ascended the throne at age sixty, he presented a fundamentally different personality than his brother. Born in Castile and immersed in Castilian politics, he saw Aragonese territories as tools for his main ambitions. He believed kings ruled by divine right with unchecked authority, declaring that "the aforesaid Majesty is not bound to give reasons for his acts, except to God." This worldview was incompatible with Catalan pactismo—the contractual theory that royal power was limited by law and custom.

The crisis stemmed from Juan's conflict with his son Charles of Viana over the inheritance of the Kingdom of Navarre. When Juan arrested Charles at Lérida on December 2, 1460, while the Catalan Corts, the Iberian equivalent of parliament, were in session, it violated multiple constitutional protections. The arrest turned a family dispute into a constitutional crisis that would last for the next decade. 

The Catalan response was quick and unprecedented. For the first time, the usually divided Catalans showed unity, as the rival Biga and Busca factions joined forces against royal oppression. As one contemporary marveled, "the union of the hearts of Catalans is such that there is no discrepancy between the rich, the middle class, and the people."

Juan's refusal to listen led to formal defiance, and the Catalans' military threat forced him into the humiliating Capitulation of Villafranca (June 21, 1461), acknowledging the revolution's legality and limiting royal authority. 

Charles's death on September 23, 1461, significantly changed the situation. He quickly became a martyr-saint in Catalan consciousness, but his death also broke apart unity as the opposition lost its unifying figure. Juan's desperation drove him to ally with Louis XI of France, literally selling Catalan territory, in particular Roussillon and Cerdagne, for military help.

The ten-year civil war wrecked Catalonia. The Catalans had looked to foreign kings for protection against their own, pledging loyalty to Castile, Portugal, and Anjou. Each intervention failed because of diplomatic isolation and internal conflicts. When Barcelona finally surrendered in 1472 after a siege and starvation, the war's destruction had permanently weakened Catalonia's position.

Meanwhile, in Castile, Enrique IV’s favoring of new favorites, especially Beltrán de la Cueva, stirred jealousy among the established nobles. The Marquis of Villena, Enrique's childhood friend and former chief minister, felt betrayed when the king awarded Cueva the mastership of Santiago—the most prestigious military order in Castile. Villena's wounded pride would soon give rise to a deadly conspiracy.

The transformation of court rivalries into rebellion started when Villena teamed up with his brother Pedro Girón and the Archbishop of Toledo, Alfonso Carrillo. They demanded the "liberation" of Enrique’s half-siblings, Alfonso and Isabel, who were living in relative obscurity at Arévalo. Their manifesto from Burgos in September 1464 accused the king of poor governance, heavy taxes, and unfairly promoting unworthy favorites. More alarmingly, they began questioning Princess Joanna's legitimacy, implying that Enrique's supposed impotence cast doubt on her parentage.

Enrique's weakness led to his downfall. Instead of quashing the localized rebellion, he opted for a compromise. The Concord of Medina del Campo (October 1464) accepted most rebel demands: Alfonso was recognized as heir and placed in Villena's custody, while Cueva was effectively exiled. This surrender only encouraged further demands that turned Enrique into a figurehead.

The "Farce of Ávila" on June 5, 1465, marked the lowest point of royal dignity. Outside the city walls, a wooden effigy representing Enrique IV was stripped of crown, scepter, and sword as charges of tyranny, heresy, and incompetence were read aloud. The eleven-year-old Alfonso was then crowned as a rival king while crowds of nobles praised the child who could not possibly rule on his own.

Multiple rebellions erupted as cities chose sides, but despite controlling a significant amount of territory and having noble support, the rebels could not achieve a decisive victory. Enrique maintained significant resources and popular backing, while his enemies were divided by personal rivalries and conflicting ambitions. The only major battle, fought at Olmedo on August 20, 1467, ended in a royal victory, but the betrayal of Segovia shortly afterward by Enrique's own treasurer showed how completely royal authority had collapsed.

The sudden death of Alfonso "XII" on July 5, 1468, at age fourteen changed everything. Officially attributed to the plague, many suspected poisoning, adding another martyr to the rebels' cause. When the nobles offered the crown to Isabel, her response showed remarkable political maturity: she refused to become a rebel puppet while maintaining that if she had any right to the throne, it came from legitimate inheritance rather than noble conspiracy. 

The rebellion's failure exposed its core weakness: without a royal figurehead, nobles couldn't maintain a unified opposition.


Isabel's refusal of the rebel crown showed both family loyalty and strategic wisdom, positioning herself as a constitutional instead of revolutionary claimant. Her upbringing at Arévalo, where she lived with her mentally ill mother, gave her unconventional lessons in adversity and the ability to tell genuine loyalty from opportunistic service.

The question of Isabel's marriage then became central to Castilian politics as various suitors made their claims. Alfonso V of Portugal, nearing sixty, sought the hand of the eighteen-year-old princess as part of a larger plan to influence Castilian affairs. His proposal received support from key nobles who believed a Portuguese alliance would benefit their interests.

However, Isabel's correspondence with Ferdinand of Aragon suggested other possibilities. Ferdinand proposed uniting the two major Christian kingdoms while keeping Castilian independence, unlike a Portuguese alliance that could lead to foreign subordination.

While Isabella was willing to accept Enrique as king, she refused to recognize his six-year-old daughter, Joanna, as the legitimate heir and started styling herself as the rightful successor. Despite Enrique's promises to his wife that he would protect Princess Joanna's inheritance rights, Isabella sought a compromise that led to the historic meeting at Los Toros de Guisando on September 18, 1468. The week-long negotiations took place at a roadside inn south of Ávila. They met in an open field within sight of the Jeronymite friary and near the ancient carved bulls that gave the place its name.  

The pact signed on September 19, 1468, represented a diplomatic compromise that temporarily resolved Castile's succession crisis. Isabella and her supporters submitted to Enrique as their sovereign, while Enrique recognized Isabella as his legitimate heir. This was achieved through the misleading argument that Enrique's marriage to Joanna of Portugal lacked proper papal dispensation for consanguinity, making Princess Joanna illegitimate under canon law and unable to inherit the throne. 

The agreement's key provision was that Isabel's future marriage needed approval from both the king and the leading nobility. 

However, the agreement failed to bring peace to the kingdom, as the noble factions remained split. Archbishop Carrillo stayed with Isabella, working to steer her away from the king and toward the Aragonese alliance. 

The Pact of Los Toros de Guisando solved Castile's immediate succession crisis, but the deeper issues that had troubled both major kingdoms throughout the century remained unaddressed. Royal authority in both Castile and Aragon had been repeatedly challenged by noble rebellion, constitutional resistance, and foreign intervention.

The agreement was a temporary compromise rather than a permanent solution. While Isabel had earned recognition as Enrique IV's heir, the questions about Princess Joanna's legitimacy remained unresolved, deliberately hidden by diplomatic language that satisfied no one completely. The king's authority to approve Isabel's marriage, along with noble consultation requirements, made future conflicts likely rather than unlikely.

The broader Iberian scene provided little hope for future stability. The Crown of Aragon remained drained from the decade-long Catalan civil war, with its Mediterranean territories ruined and its constitutional disputes unresolved. Juan II's victory had technically restored royal authority, but at a huge expense to the Crown's economy and public support. Meanwhile, Portugal's successful Atlantic expansion and France's control of Roussillon and Cerdagne showed how Iberian fragility allowed foreign powers to take advantage.

When Isabel secretly married Ferdinand of Aragon in 1469 without royal approval, she triggered the very succession crisis the Los Toros de Guisando pact aimed to prevent.

In our next episode, the marriage between Isabel and Ferdinand and the war for the Castilian succession.

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