Treaty Of Alcáçovas: Background, Causes And Consequences

The Treaty of Alcáçovas was an agreement signed between the kingdoms of Castile and Portugal, celebrated in the Portuguese town of the same name in 1479. It had two objectives: to end the civil war caused by the succession of the Kingdom of Castile and to delimit the properties and rights of each kingdom in the Atlantic Ocean.

This treaty is also known as the Peace of Alcaçovas-Toledo or the Treaty of Alcáçovas-Toledo. By means of this treaty, the property of the Canary Islands was transferred to the kingdom of Castile. As compensation, Portugal was granted other possessions in West Africa.

Treaty of Alcáçovas

In principle, the treaty was signed by the ambassadors of Castile and Portugal on September 4, 1979. On September 27, it was ratified by the kings Isabel and Fernando II of Castile and Aragon, and in 1780 by the kings of Castile and Portugal.

The most relevant consequence of the treaty was the delay in the expedition of Christopher Columbus to the New World.


The problems between the kingdoms of Castile and Portugal began with the succession to the Castilian throne. In 1474, on the death of Enrique IV, King of Castile, there was a confrontation between the nobility. The ascension to the throne of the only daughter of Enrique IV, Juana la Beltraneja, was questioned because it was believed that she was not a legitimate daughter.

On the other side was Isabel la Católica (of Castile), stepsister of King Enrique, who also claimed the throne. Isabel was supported by her husband, King Ferdinand of Aragon, and Juana had the support of her fiancé, King Alfonso V of Portugal, as well as a good part of the Castilian high nobility. The rest of the nobility supported Isabel.

The Castilian civil war broke out in 1475. The confrontations for the occupation of territories in the northern plateau of Castile ended in 1476 in favor of Isabel with the battle of Toro.

Hostilities continued at sea between the Portuguese and Castilian fleets; both competed for the fisheries and mineral riches they extracted from Guinea in Africa.

The frictions between Portugal and Castile had been going on for a long time due to the exploitation of the fishing riches of the Atlantic Ocean. Both kingdoms forced merchants and fishing fleets to pay taxes, but the controversy arose because it was not known to which kingdom they really corresponded.

The control of the territories of La Mina and Guinea, rich in precious metals (especially gold) and slaves, was key in the conflict. The other was the law on the Canary Islands. The Portuguese had been benefited by papal bulls between 1452 and 1455 to control various territories of Guinea.

With such permits, Portuguese vessels used to assault Castilian ships loaded with goods from Guinea.

This was the antecedent that led to the diplomatic confrontation between both kingdoms. However, King Henry IV of Castile preferred not to escalate hostilities.

Despite the defeat of the Castilians at sea, Portugal could not win the war on land. Then, in 1479, the peace negotiations began.


At the beginning of the war, in August 1475, Queen Isabel I of Castile began the naval confrontation in the Atlantic Ocean. Having taken possession of the kingdom, he authorized the Castilian ships to transit and navigate freely without the permission of Portugal. The queen claimed the territories of Africa and Guinea as her own.

King Alfonso V of Portugal did not agree in any way that his niece Juana had been ousted from the Castilian throne. Alfonso obtained a papal permission to marry his own niece. Its objective was to unite the kingdoms of Portugal and Castile.

Seeing his plans to expand the Portuguese kingdom defeated, Alfonso formed an army to claim the Castilian throne. He based his claim on the fact that he and Juana were the legitimate heirs to the throne of Portugal, Castilla y León.

As for overseas trade, King Alfonso sought to benefit from maritime trade in Africa and the Atlantic. He granted permits to foreign merchants subject to Portugal in exchange for paying taxes. When being harmed, the kingdom of Castile also implemented this “open” trade policy.


The first major consequence of the signing of the Treaty of Alcáçovas was the delay in Columbus’s expedition to America. Some historians believe that the real reason for the delay of the Catholic kings to authorize Columbus’s trip was the legal uncertainty around the ownership of the territories and waters to be discovered.

There is a controversy among historians on this point. Some believe that the Treaty of Alcáçovas only referred to the “sea of ​​Africa”. That is, the waters already discovered adjacent to the African continent that were occupied by Portugal and Castile.

Others consider that the Treaty granted Portugal rights over the entire Atlantic Ocean, except the Canary Islands. According to this interpretation, all the islands and territories discovered by Christopher Columbus belonged to Portugal, because the treaty establishes Portugal’s ownership of “the lands and waters to be discovered”.

According to this criterion, the delay of the kings Isabel and Fernando to authorize the expedition of Columbus was deliberate. The trip was authorized once the kings of Castile were sure of the ascension to the throne of Alexander VI (Rodrigo Borgia), who was their ally.

They were aware that any controversy with Portugal for this reason would be immediately neutralized by means of a papal bull.

Treaty of Tordesillas

Portugal’s protest was swift, which sparked a series of new diplomatic negotiations between the two kingdoms.

As planned, in 1493 the Catholic kings obtained several papal bulls (Alexandrian bulls); These bulls established a new division of the Atlantic Ocean, effectively repealing the Treaty of Alcáçovas.

Before Columbus’s second voyage, the Portuguese reminded him of the ban on touching the territories of Guinea and the Mine in Africa.

The protests of King Juan of Portugal concluded with the signing of the Treaty of Tordesillas in 1494, in which a new distribution was made a little more favorable to Portugal than that established in the Alexandrian bulls.

Moura third parties

The Treaty of Alcáçovas established the recognition of Isabel as Queen of Castile and the transfer of the Canary Islands to the Spanish kingdom. In addition, the monopoly of Portuguese trade in Africa and the exclusive collection of the tax (fifth real) were recognized.

Apart from this, this treaty resulted in other agreements negotiated in parallel, known as the Tercerías de Moura. In these it was established that the princess Juana de Castilla (Juana la Beltraneja) had to renounce all her rights and titles in the kingdom of Castile.

Likewise, Juana had to choose between marrying Prince Juan de Aragón y Castilla, heir to the Catholic kings Isabel and Fernando, or cloistered for 14 years in a convent. She decided the latter.

Another of the agreements was the wedding of the Infanta Isabel de Aragón, the first-born of the Catholic kings, with Prince Alfonso, the only son of King Juan II of Portugal.

The gigantic dowry paid by the Catholic kings in this marriage was considered a war indemnity to Portugal.


  1. Foundations of the Portuguese Empire, 1415-1580. Retrieved on March 31, 2018 from
  2. Treaty of Alcaçovas. Retrieved from
  3. The Treaty of Alcáçovas-Toledo. Consulted of
  4. Treaty of Alcaçovas. Consulted from
  5. Treaty of Alcáçovas. Consulted of
  6. Treaty of Alcaçovas. Consulted of

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