John II of Portugal takes throne and launches African expansion

John II ascended the throne of Portugal in 1481 and immediately embarked upon measures to exploit his monopoly of European trade in Guinea, to lay the foundations of a Portuguese empire in Africa, and to seek Prester John. His program included the construction of the fortress of São Jorge da Mina, assumption of the title of Lord of Guinea, the voyages of Diogo Cão to the Congo and Angola, colonisation of São Tomé, and the despatch of envoys into the African interior. It was this African policy that led to the decision to send João Afonso d'Aveiro inland to Benin.