Castile and Portugal signed the Treaty of Alcáçovas, ending the War of the Castilian Succession and recognizing Portuguese primacy over much of the Atlantic island groups and the Guinea coast—an important diplomatic backdrop to late-15th-century Portuguese Atlantic–African expansion.
The Portuguese established Castelo de São Jorge da Mina (Elmina Castle) on the Gold Coast as a fortified trading post to secure and channel commerce (notably gold) along the Gulf of Guinea—an anchor point for subsequent coastal voyages.
Navigator Diogo Cão became the first European recorded to reach the mouth of the Congo River and erected a stone pillar (padrão) asserting Portuguese presence, extending reconnaissance and claims along West Central Africa.
On a second expedition down the southwest African coast, Diogo Cão reached Cape Cross (in present-day Namibia), pushing Portuguese knowledge further south prior to the Cape-rounding breakthrough.
Bartolomeu Dias sailed from Lisbon with a small squadron to extend exploration beyond prior limits and search for a sea route around Africa—setting the stage for the first successful rounding of the continent’s southern end.
After being blown into the South Atlantic and turning eastward, Dias’s ships made landfall on the southern African coast (east of the Cape of Good Hope), showing that the expedition had passed the continent’s southern tip even before sighting it.
Dias’s expedition planted a stone marker (padrão) at Kwaaihoek, marking the easternmost point of the voyage along the southern African coast and symbolizing Portuguese claims associated with exploration.
On the homeward leg, Dias’s ships passed close enough to sight the Cape of Good Hope area (often dated to May 1488). The cape’s naming is debated in sources, but the voyage decisively demonstrated the feasibility of reaching the Indian Ocean by sea.
Dias returned to Lisbon after roughly 16 months away, having rounded the southern end of Africa and revealed a workable route into the Indian Ocean system—critical groundwork for later expeditions to East Africa and India.
Portugal and Castile signed the Treaty of Tordesillas, adjusting the Atlantic line of demarcation and aiming to reduce conflict over overseas expansion—an important legal framework as Portuguese navigation increasingly used the Atlantic approach to round Africa.
Vasco da Gama left Lisbon with four ships to reach India by sea, explicitly building on navigation knowledge from earlier Atlantic–African exploration, including the oceanic route used to approach and round southern Africa.
Da Gama’s fleet rounded the Cape of Good Hope, validating the Cape passage as a repeatable corridor for state-sponsored fleets and accelerating Portuguese movement from Atlantic coastal exploration toward sustained Indian Ocean operations.
Portuguese Cape rounding and early Atlantic–African coastal exploration (1480–1500)
