Exploration
John II famously restored the policies of Atlantic exploration, reviving and broadening the work of his great-uncle, Henry the Navigator. The Portuguese explorations were his main priority in government, patronising both local and foreign men, such as João Afonso de Aveiro and Martin Behaim, to further his goals. Portuguese explorers pushed south along the known coast of Africa with the purpose of discovering the maritime route to India and breaking into the spice trade. During John II's reign, the following achievements were realised:
1482 – Foundation of the coastal fortress and trade post of São Jorge da Mina.
1484 – Discovery of the Congo River by Diogo Cão.
1488 – Discovery and passage of the Cape of Good Hope by Bartolomeu Dias in Mossel Bay.
1493 – Start of the settlement of the São Tomé and Príncipe islands by Álvaro Caminha.
Funding of land expeditions by Afonso de Paiva and Pêro da Covilhã to India and Ethiopia in search of the kingdom of Prester John.
In 1484, John appointed a Maritime Advisory Committee, the Junta dos Mathematicos, to supervise navigational efforts and provide explorers with charts and instruments.
Around the same time, Christopher Columbus proposed his planned voyage to John. The king relegated Columbus's proposal to the Committee, who rejected it, correctly, on the grounds that Columbus's estimate for a voyage of 2,400 nmi was only a quarter of what it should have been. In 1488, Columbus again appealed to the court of Portugal, and John II again granted him an audience. That meeting also proved unsuccessful, in part because not long afterwards Bartolomeu Dias returned to Portugal with news of his successful rounding of the southern tip of Africa (near the Cape of Good Hope). Columbus then sought an audience with the Catholic Monarchs and eventually secured their support.
While returning home from his first voyage early in 1493, Columbus was driven by storm into the port of Lisbon. John II welcomed him warmly but asserted that under the Treaty of Alcáçovas previously signed with Spain, Columbus's discoveries lay within Portugal's sphere of influence. The king then prepared a fleet under Francisco de Almeida to claim the new islands. Anxious to avoid war, the Catholic Monarchs arranged negotiations in the small Spanish town of Tordesillas. The result of this meeting would be the famous Treaty of Tordesillas, which sought to divide all newly discovered lands in the New World between Spain and Portugal.