Treaty of Alcáçovas

The Treaty of Alcáçovas (also known as Treaty or Peace of Alcáçovas-Toledo) was signed on 4 September 1479 between the Catholic Monarchs of Castile and Aragon on one side and Afonso V and his son, Prince John of Portugal, on the other side.It put an end to the War of the Castilian Succession, which ended with a victory of the Catholic Monarchs on land[1] and a Portuguese victory on the sea.[2][1] The four peace treaties signed at Alcáçovas reflected that outcome: Isabella was recognized as Queen of Castile while Portugal reached hegemony in the Atlantic Ocean.

The treaty intended to regulate:

  • The renunciation of Afonso V and Catholic Monarchs to the Castilian throne and Portuguese throne, respectively
  • The division of the Atlantic Ocean and overseas territories into two zones of influence
  • The destiny of Juana de Trastámara
  • The contract of marriage between Isabella, the eldest daughter of the Catholic Monarchs, with Afonso, heir of Prince John. This was known as Tercerias de Moura, and included the payment to Portugal of a war compensation by the Catholic Monarchs in the form of marriage dowry.[3]
  • The pardon of the Castilian supporters of Juana

War of the Castilian Succession

Ferdinand and Isabella

After Henry's IV death in 1474, the Castilian crown was disputed between the half-sister of the king, Isabella I of Castile, married to Prince Ferdinand II of Aragon, and the king's daughter, Juana de Trastámara, popularly known as la Beltraneja – because her father was alleged to be Beltrán de la Cueva. In the subsequent civil war, Afonso V of Portugal married Juana and invaded Castile (May 1475), defending her rights.[4]

Parallel to the dynastic struggle, there was a fierce naval war between the fleets of Portugal and Castile to access and control overseas territories − especially Guinea – whose gold and slaves were the heart of the Portuguese power. The main events of this war were the indecisive[5][6] battle of Toro (1 March 1476), transformed[7] in a strategic victory by the Catholic Monarchs and the battle of Guinea[8] (1478), which granted Portugal the hegemony in the Atlantic Ocean and disputed territories.

Historian Stephen R. Bown wrote:[9]

When Ferdinand an Isabella secured their rule after the Battle of Toro on 1 March 1476- effectively eliminating the threat of Portuguese invasion but not officially ending the war- they renewed the twenty-year-old Castilian claim to their "ancient and exclusive" rights to the Canary Islands and the Guinea coast .... They encouraged Spanish merchant ships to take advantage of the political disruption and considered making direct attacks on Portuguese vessels returning from Guinea, with the objective of seizing the monopoly.... In 1478 a Spanish fleet of thirty-five caravels was intercepted by an armed Portuguese squadron. Most of the fleet was captured and taken to Lisbon. [I]n 1479 ... the two nations concluded terms for peace with the treaty of Alcáçovas, ending the struggle for the succession as well as their battle at sea.