section_path: Early expansion/Rivalry with Portugal
section_name: Rivalry with Portugal
paragraph_text: Rivalry with Portugal
  
  The Portuguese tried in vain to keep secret their discovery of the Gold Coast (1471) in the Gulf of Guinea, but the news quickly caused a huge gold rush. Chronicler Pulgar wrote that the fame of the treasures of Guinea "spread around the ports of Andalusia in such way that everybody tried to go there". Worthless trinkets, Moorish textiles, and above all, shells from the Canary and Cape Verde islands were exchanged for gold, slaves, ivory and Guinea pepper.
  
  The War of the Castilian Succession (1475–79) provided the Catholic Monarchs with the opportunity not only to attack the main source of the Portuguese power, but also to take possession of this lucrative commerce. The Crown officially organized this trade with Guinea: every caravel had to secure a government license and to pay a tax on one-fifth of their profits (a receiver of the customs of Guinea was established in Seville in 1475—the ancestor of the future and famous Casa de Contratación).
  
  Castilian fleets fought in the Atlantic Ocean, temporarily occupying the Cape Verde islands (1476), conquering the city of Ceuta in the Tingitan Peninsula in 1476 (but retaken by the Portuguese), and even attacked the Azores islands, being defeated at Praia. The turning point of the war came in 1478, however, when a Castilian fleet sent by King Ferdinand to conquer Gran Canaria lost men and ships to the Portuguese who expelled the attack, and a large Castilian armada—full of gold—was entirely captured in the decisive Battle of Guinea.
  
  The Treaty of Alcáçovas (4 September 1479), while assuring the Castilian throne to the Catholic Monarchs, reflected the Castilian naval and colonial defeat: "War with Castile broke out waged savagely in the Gulf until the Castilian fleet of thirty-five sail was defeated there in 1478. As a result of this naval victory, at the Treaty of Alcáçovas in 1479 Castile, while retaining her rights in the Canaries, recognized the Portuguese monopoly of fishing and navigation along the whole west African coast and Portugal's rights over the Madeira, Azores and Cape Verde islands." The treaty delimited the spheres of influence of the two countries, establishing the principle of the Mare clausum. It was confirmed in 1481 by the Pope Sixtus IV, in the papal bull Æterni regis (dated on 21 June 1481).
  
  However, this experience would prove to be profitable for future Spanish overseas expansion, because as the Spaniards were excluded from the lands discovered or to be discovered from the Canaries southward —and consequently from the road to India around Africa —they sponsored the voyage of Columbus towards the west (1492) in search of Asia to trade in its spices, encountering the Americas instead. Thus, the limitations imposed by the Alcáçovas treaty were overcome and a new and more balanced division of the world would be reached in the Treaty of Tordesillas between both emerging maritime powers.