Medieval Iberian Kingdoms: Castile and Aragon’s Political Evolution

Posted on Jun 17, 2025 in International Relations

Castile: Administration and Governance

Administrative Structure

Castile’s administrative territorial division included 7 provinces, known as adelantamientos (border provinces) and merindades (inland provinces).

Municipal Councils & Royal Influence

Municipal councils were controlled by regimientos, whose most prominent figure was the corregidor. Tax officials began to appear in León, becoming part of the Royal Council when they served as procuradores of cities, where they protested the handling of moneda (currency). The cities were the mainstay of the Crown against the nobility. Subsidies served to benefit the Crown in exchange for maintaining the value of the moneda.

In the 14th century, Castile and León were unified. They played an important role in the 14th century in dealing with political issues, but in many cities in the 15th century, they lost their representation, which was given to the nobility. The nobility and clergy stopped attending, thus losing their central administrative influence.

Aragon: Institutions and Power Dynamics

The Aragonese Cortes and Generalitat

The Cortes, which controlled the Crown and were integrated by the nobility, church, and civic elite, were called síndicos. They defended feudal interests against the Crown’s attempts to impose its authority.

The Catalan Cortes under Peter IV formed a commission, the Generalitat (autonomous), responsible for defending the nobility’s estamental privileges against the king, to ensure compliance with agreements when the Cortes were not meeting, and for raising taxes for the king. The Cortes had granted important powers, such as the presentation of grievances by each estate against the King’s decisions that were considered “against the law,” and they had legislative authority.

Defenders of Privilege: Justicia, Biga, Busca

  • The Justicia de Aragón: An office charged with defending aristocratic privilege against the King.
  • BIGA: Consisted of big merchants and senior rentiers who dominated municipal imports.
  • BUSCA: Integrated by master craftsmen and small merchants who wanted to control local power and improve their economic situation.

Political Conflicts: Rise of Authoritarian Monarchy

The disintegration of the feudal vassal system led to the appearance of authoritarian monarchy. The king gained power, and nobles lost it. Relying on Roman law, the king governed by laws applicable to all his kingdom.

Castile: Royal Authority vs. Nobility

Early Minorities & Dynastic Wars

  • During the minorities of Ferdinand IV and Alfonso XI, the kingdom was governed by Doña María de Molina, who was supported by Alfonso XI until he came of age, according to the Law of Alcalá.
  • War between the son of Alfonso XI, Pedro I (supported by Jews and the lower nobility), and Enrique de Trastámara (supported by the aristocracy, Aragon, and France). It concluded in the fields of Montiel with the consequence of mercedes (royal grants).

Juan II & Enrique IV: Power Struggles

This period coincided with the reigns of Juan II and Enrique IV. Juan II was a child, and his uncle Ferdinand of Antequera was appointed regent, who later reigned as King of Aragon. The reign of Juan II was presented as a struggle between the monarchy, the Princes of Aragon, and the high nobility. The King’s favorite, Don Álvaro de Luna, was presented as a defender of royal authority and faced the victorious nobility. Enrique IV was forced to appoint his brothers Alfonso and Isabella as heirs, limiting his daughter Juana. When Isabella married Ferdinand of Aragon, the nobility recognized Juan as the legitimate heir, leading to a civil war between his supporters and those of Isabella (Alfonso had died). This war ended with the Treaty of Alcáçovas.

Aragon: Succession and Civil Strife

Peter IV the Ceremonious & Noble Resistance

During the reign of Peter IV the Ceremonious, he faced the nobles of Aragon and Valencia in an attempt to establish institutions to govern his kingdoms. The immediate cause was the appointment of his daughter Constance as heir. The Aragonese and Valencian nobility gathered around the king’s brother, James of Urgell. The king defeated the rebels at the Battles of Epila and Mislata and superseded all noble privileges.

The Compromise of Caspe and Succession

Martin I’s death without issue and without a will caused a power vacuum in the Crown of Aragon for two years. The kingdoms were divided and simultaneously supported various pretenders to the crown. Among them stood James of Urgell and Ferdinand of Antequera, regent for Juan II of Castile. The solution to the conflict was found in the Compromise of Caspe, where representatives from the three kingdoms (Catalonia, Aragon, and Valencia) chose a sovereign by vote, and Ferdinand of Antequera was elected, who then tried to establish an authoritarian monarchy.

Juan II’s Reign: Confrontation and Civil War

Corresponds to the reign of Juan II, who confronted the cities, the clergy, and the nobility. The cause of this confrontation was the disagreements between the king and his heir, the Prince of Viana. His imprisonment in Lleida detonated a civil war that ruined the country.