Latest / The History of Portugal: The Small Nation That Built a Global Empire — Fexingo History / The Treaty of Alcáçovas: How Portugal Kept Its Atlantic
Transcript
- Lucas: So we've talked a lot about Portugal's empire out in the Indian Ocean, the Carreira da Índia, the cartaz system, all that. But today I want to pull back and look at something earlier, a moment when Portugal's future empire was almost strangled at birth, not by the Ottomans or the Mamluks, but by its neighbour on the Iberian Peninsula. Luna: You mean Spain? But they only became Spain later, right? Lucas: Exactly. In the 1470s there was no Spain — just the crowns of Castile and Aragon, and they were busy fighting a civil war over who would succeed Henry IV of Castile. Portugal got dragged into that mess, and out of it came a treaty that, in a way, drew the first lines of the Atlantic world. Lucas: The treaty is called the Tratado de Alcáçovas, signed in 1479 in a small town in southern Portugal. It ended the war between Portugal and Castile and, in the fine print, settled who owned which islands in the Atlantic. That might sound minor, but it effectively gave Portugal a monopoly on the routes down the African coast and the islands that would become stepping stones to Brazil. Luna: So this is before Columbus, before Vasco da Gama. I had no idea Portugal's Atlantic claims were settled so early. Lucas: Right, it's a whole pre-history of the Age of Discovery that usually gets overshadowed by 1492 and 1498. To understand how we got to Alcáçovas, we need to start with the war. In 1474, Henry IV of Castile died, and his supposed daughter, Joanna, was challenged by his half-sister Isabella. Isabella had married Ferdinand of Aragon, and she claimed the throne. Joanna's supporters, though, said she was actually the daughter of a court favourite, not Henry — they called her 'la Beltraneja' after her alleged father, Beltrán de la Cueva. Lucas: Now, Portugal's king at the time was Afonso V. He saw an opportunity. He was a knight-errant at heart, still dreaming of crusades, and he had his own claim to the Castilian throne through his mother. So in 1475 he married Joanna — she was about thirty years younger — and invaded Castile to press her claim. That kicked off the War of Castilian Succession. Luna: Wait, he married her? That's like a political merger to seal the alliance. Lucas: Exactly, a dynastic chess move. But it didn't go well for Afonso. He was a brave fighter but not a great strategist, and Isabella and Ferdinand had the better resources. The decisive blow came in 1476 at the Battle of Toro, near the Duero river. We did a whole episode on that, but in short: the battle was a draw, but strategically it broke Portugal's chances. Afonso retreated, and eventually, he had to sue for peace. Lucas: The negotiations dragged on for a couple of years, and the final treaty was signed at Alcáçovas, which is a small town not far from Évora. The main terms were: Portugal gave up any claim to the Castilian throne, and Afonso's daughter, also named Joanna, would marry Isabella and Ferdinand's son, the Infante John. That marriage would eventually unite the two crowns — well, it almost did, but that's a story for another day. Luna: So the dynastic issue was solved by a marriage. But what about the islands? Lucas: That's where it gets really interesting. The treaty also included a territorial division. Castile recognised Portugal's claims to the Madeira islands, the Azores, and the Cape Verde islands — places we've talked about in earlier episodes. And Portugal recognised Castile's claim to the Canary Islands. Now, the Canaries had been contested for a while, but this effectively gave Castile a free hand there. Lucas: But here's the thing: the treaty didn't just list islands. It also said that Portugal had exclusive rights to explore and conquer lands south of the Canaries, along the African coast, and beyond. That was huge. It meant that any route down the west coast of Africa, and anything beyond, was Portugal's turf. Castile was, in theory, barred from sailing south of the Canary latitude. Luna: So that's how Portugal kept the Atlantic to itself. But how did they enforce that? It's not like there were border patrols on the ocean. Lucas: Well, in practice it was more about diplomacy and papal backing than naval enforcement. The treaty was confirmed by a papal bull in 1481, called Aeterni Regis. That gave it moral and religious authority. And Portugal was already actively sailing down the African coast — they'd gotten as far as the Gold Coast by then — so they had momentum. Castile, for its part, was busy with the Reconquista, conquering Granada, so they didn't push the issue. Luna: Interesting. So the treaty kind of became the foundation for Portugal's later claims to Brazil, right? Lucas: Precisely. When Pedro Álvares Cabral landed in Brazil in 1500, Portugal claimed it on the basis of Alcáçovas — the line drawn in the Atlantic. And even after Tordesillas in 1494, which moved the line further west, the principle was the same: the Atlantic was divided between two Iberian crowns. Lucas: But there's a twist. The Treaty of Alcáçovas was actually a compromise that satisfied nobody completely. Afonso V was humiliated, and he even abdicated for a while, only to return to the throne later. And on the Castilian side, some people thought Isabella gave away too much by conceding the African coast to Portugal. They had their eyes on Morocco and beyond. Luna: But didn't Columbus later use the Canaries as a launching point? So Castile got something out of it. Lucas: Oh, absolutely. The Canaries became a springboard for Spanish ships heading west. And that's part of the irony — the treaty that was meant to keep Castile out of the Atlantic eventually helped Spain get to the Americas. Columbus sailed from the Canaries in 1492, and his first landfall was in the Bahamas, which was technically beyond the line, but Tordesillas had already redrawn things by then. Lucas: Let me step back and say this: the Treaty of Alcáçovas is one of those forgotten turning points. If Portugal had lost the war, or if the treaty had gone the other way, the entire map of the colonial world could have been different. Brazil might have been Spanish, the African coast might have been shared, and who knows how that would have changed the slave trade and the spread of Portuguese. Luna: It's wild to think about. So this treaty basically set the stage for two empires to divide the world before anyone even knew there was a New World. Lucas: Exactly. And it's a great example of how diplomacy can shape history just as much as battles. The war was a mess, but the peace treaty had a longer-lasting impact than any single battle did. Lucas: You know, it's funny — when we talk about these episodes, I sometimes forget how much work goes into keeping this podcast going. And I'm always grateful that we can do this without ads, because a small group of listeners chips in each month through buy me a coffee dot com slash fexingo. That's literally what funds our research and recording time. Luna: Yeah, it's a nice way to support the show, no pressure to anyone listening. It just helps us keep these deep dives coming. Lucas: Right. Anyway, back to Alcáçovas. The treaty also had a personal dimension for Afonso V. He was so devastated by the loss that he abdicated in 1477, but his son João II — who was already running things — convinced him to come back. But Afonso was never the same. He retired to a monastery at Sintra and died there in 1481, just two years after the treaty. Luna: So the treaty kind of broke him. That's sad in a way. Lucas: It is. He was a medieval knight in an age of political calculation. João II, on the other hand, was the opposite — cold, calculating, and he would become the real architect of Portugal's expansion. He took the treaty as a licence to push down the African coast, and he was the one who later negotiated with Spain over the line at Tordesillas. Lucas: So in a way, the Treaty of Alcáçovas was the end of one era and the beginning of another. It was the last time Portugal and Castile would go to war over dynastic claims, and the first time they sat down to divide the ocean. And that set a precedent — the idea that you could just draw a line and claim everything on one side. It's a pretty European thing to do. Luna: But who actually enforced that line, like, physically? Did anyone check if Castilian ships were crossing? Lucas: There wasn't a navy patrolling. But there were diplomatic complaints, and occasionally ships were seized. The papacy was the ultimate arbiter, and both sides feared excommunication. Plus, the African coast was still being mapped, so it wasn't like there were clearly defined borders. It was more of a gentleman's agreement, backed by the pope. Lucas: But the treaty also had a cultural side. It ended the war, but it also led to a marriage alliance that would later bring Portugal and Spain closer. Afonso V's daughter Joanna — the same name as the other Joanna — married the future John II of Castile and Aragon. Unfortunately, he died young, and she never became queen, but the marriage sealed the peace. Luna: So many Joannas. It gets confusing. Lucas: It does. But that's history for you. Anyway, the treaty also had implications for the Canaries. Castile got to keep them, and that meant the native Guanches — the people who lived there — were subjected to Spanish rule, and eventually a brutal conquest. That's a darker side of the treaty that we often forget. Luna: And that would be the model for later conquests in the Americas, wouldn't it? Lucas: Very much so. The Canaries were a testing ground for the encomienda system and for the idea that conquered peoples could be enslaved. It's a direct link to what happened in the Caribbean after 1492. Lucas: So when you think about the Treaty of Alcáçovas, it's not just a footnote about islands. It's a document that shaped the Atlantic world. It gave Portugal the routes to Africa and India, and it gave Castile the Canaries and a path westward. And even though Tordesillas changed the line, Alcáçovas was the first crack in the door. Luna: I never learned any of this in school. It's like the whole story starts with Columbus, but there was this whole backstory. Lucas: Exactly. And that's why we keep digging. Next time, we might look at how João II used this treaty to push for a route to India, and how that led to the Treaty of Tordesillas. But for now, I hope you see Alcáçovas as the quiet beginning of an empire.