Three wars and a marriage treaty that failed to unite Portugal and Castile
The Fernandine Wars were a trio of medieval conflicts sparked by a disputed succession. King Ferdinand I of Portugal fought the Crown of Castile for years, eventually attempting to secure peace through a complex marriage pact. Yet, this diplomatic effort ultimately collapsed, triggering a national crisis and a fight for independence.
The Fernandine Wars, occurring between 1369 and 1382, were a series of three distinct military engagements between the Kingdom of Portugal and the Crown of Castile. These conflicts were rooted in the death of King Peter of Castile in 1369, which prompted Ferdinand I of Portugal to assert his own claim to the Castilian throne. This struggle was not an isolated regional dispute but functioned as a component of the broader Hundred Years' War, drawing the two Iberian powers into a cycle of hostility that lasted over a decade.
In 1383, the two kingdoms sought to resolve their differences through the Treaty of Salvaterra de Magos. To solidify this peace, Ferdinand I arranged the marriage of his daughter, Beatrice, to King John I of Castile. The treaty was meticulously designed to prevent the total absorption of Portugal by its neighbor. It stipulated that upon Ferdinand's death, his wife, Queen Leonor Telles de Menezes, would serve as regent until a son born to Beatrice and John reached the age of 14. The agreement included specific clauses to ensure the kingdoms remained separate, requiring the consent of the Cortes for any potential unification.
Despite these elaborate legal safeguards, the arrangement failed to hold. The succession plans were challenged during the Portuguese interregnum, a period of civil war lasting from April 1383 until August 1385. During the famous Cortes of Coimbra in 1385, the lawyer João das Regras argued that the Treaty of Salvaterra had been breached, effectively barring Beatrice and John I of Castile from the Portuguese throne. This legal maneuver paved the way for John, Master of Aviz, to claim the crown, marking a definitive end to the diplomatic experiment and the conclusion of the Fernandine era.
Source: Fernandine Wars
