The Treaty of Tordesillas and Rivalry with Portugal
A Diplomatic Crisis Made by Columbus
When Columbus sailed into Lisbon harbour on his return voyage in March 1493, King John II of Portugal was waiting. The Portuguese crown understood almost immediately that something had gone wrong for them. For nearly a century Portugal had invested in the African route to Asia: the fort at El Mina, decades of royally funded voyages under Prince Henry, the rounding of the Cape of Good Hope by Bartolomeu Dias in 1488. A westward Castilian voyage that claimed to have reached Asian islands threatened all of that overnight. King John warned Columbus that under previous treaties the new lands belonged to Portugal — an opening shot in what could easily have become a Iberian war.
The papal bull Inter caetera (1493) drew a line 100 leagues west of the Cape Verde Islands; the Treaty of Tordesillas (1494) moved it to 370 leagues west — far enough to give Portugal an unintended claim on Brazil in 1500.
The Papal Solution: Inter Caetera (1493)
Ferdinand and Isabella moved fast. Their man in Rome was Rodrigo Borgia, who had become Pope Alexander VI just the previous year. Pope Alexander was Spanish-born, depended on Ferdinand and Isabella’s backing in Italian politics, and had no wish to side with Portugal. In May 1493 he issued the papal bull Inter caetera, drawing a line of demarcation from pole to pole, 100 leagues west of the Cape Verde Islands. Everything west of the line was reserved for Spain; everything east, including the African route, was Portugal’s. The bull explicitly framed Spanish exploration as a duty to spread Christianity, allowing Ferdinand and Isabella to present any seizure of land as a religious mission rather than naked conquest.
For Spain, this was a gift: a religiously underwritten title to half the unknown world before they had any clear idea what was in it. For Portugal, the line was unacceptable. King John II protested that the boundary cut too close to Portuguese-held islands and ignored Portuguese knowledge that land lay in the western Atlantic closer than Inter caetera assumed.
The Treaty of Tordesillas, 7 June 1494
Rather than risk war, the two crowns negotiated directly. Their representatives met at Tordesillas, a small town in Castile on the river Duero. The resulting Treaty of Tordesillas, signed on 7 June 1494, moved the line significantly westward, to 370 leagues west of the Cape Verde Islands. In return, Portugal accepted Spanish title to everything west of the new line. The pope ratified the new line in 1506. From a Castilian point of view, this looked like a concession; from John II’s point of view, it was a victory bought with quiet inside knowledge.
Tordesillas only divided the ‘new world’ between Spain and Portugal — it had no consultation with anyone living in the lands divided. The Indigenous peoples of the Americas, the Tainos, Mexica, Inca, Quechua and dozens more, were not party to the treaty and would not have recognised either crown’s authority. The treaty also said nothing about the rest of Europe: France, England and the Netherlands all eventually rejected its legitimacy and built their own American empires anyway. So Tordesillas was decisive between two crowns — and irrelevant to most of the people whose lives it affected.
Alexander VI — Rodrigo Borgia — was Spanish-born from Valencia. He had secured his election in 1492 with promises and payments to Italian cardinals, was a controversial figure even by the standards of the Borgia family, and depended on Ferdinand and Isabella’s political backing in Italian disputes. Issuing Inter caetera in their favour cost him nothing politically and earned him Spanish gratitude. Critics at the time and since have argued that the bull was less a neutral religious decision than a political favour — a reminder that papal authority in this period operated inside European power politics, not above them.
The Cabral Surprise (1500)
Why did King John II push so hard for the line to be moved further west? Portugal had been gathering reports for years that land lay much closer to the African coast in the southern Atlantic than the original bull assumed. Six years after Tordesillas, Pedro Álvares Cabral was sailing for India when his fleet, taking the wide southern Atlantic curve to catch the trade winds, made landfall in 1500 on what is now Brazil — east of the new line. Brazil therefore fell to Portugal entirely by Tordesillas’ definition. Whether Cabral’s landing was an accident or a deliberate confirmation of insider Portuguese knowledge is still debated. What is not debated is that the renegotiated line gave Portugal a foothold in the Americas it would otherwise not have had.
Why Tordesillas Mattered for the Period
For the option as a whole, Tordesillas matters in three ways. First, it gave Spain unchallenged Catholic title (within Europe) to everything west of the line, which Cortes, Pizarro and the encomenderos would later use to justify conquest. Second, it embedded a religious framing that Spanish colonialism never abandoned: the ‘Requerimiento’ (drafted 1513) was based on the papal donation. Third, it became the template for later imperial agreements — European powers dividing the rest of the world among themselves without consulting any of its inhabitants. Tordesillas is therefore not just a date to remember; it is the legal scaffolding for the whole Spanish enterprise that follows.
Tordesillas underwrote Spanish claims throughout the conquest era: it justified Spanish title in Catholic eyes, framed conquest as a Christian mission (used in the 1513 Requerimiento), and inadvertently gave Portugal Brazil after Cabral’s 1500 landing.
A Treaty No One Else Recognised
It is worth ending on the limits of Tordesillas. France’s King Francis I famously demanded to see ‘the clause in Adam’s will’ that gave the world to Spain and Portugal. England, the Netherlands and France all eventually built American empires in defiance of the treaty — the very fact that they had to defy it shows how serious a tool of legitimacy it had become for the Spanish and Portuguese crowns. Indigenous peoples never recognised it. Within the Catholic Iberian world, however, Tordesillas gave Spanish empire-builders a piece of paper that turned conquest into mission, and that paper would be cited in encomienda awards, viceroyalty grants and missionary orders for the next 250 years.