In the year 1480, the valiant King Don Alphonzo died, and was succeeded by his son Don John II. who, in 1481, gave orders to Diego d’Azambuxa to construct the castle of St George del Mina, on the African coast.  In 1484, Diego Caon, a knight belonging to the court, discovered the coast as far as the river Congo, on the south side of the line, in seven or eight degrees of latitude[14], where he erected a stone pillar, with the royal arms and titles of Portugal, with the date of his discovery.  He proceeded southwards from thence along the coast, all the way to a river near the tropic of Capricorn, setting up similar stone pillars in convenient places.  He afterwards returned to Congo, the king of which country sent ambassadors by his ship into Portugal.  In the next year, or the year following, John Alonzo d’Aveiro brought home from Benin pepper with a tail[15], being the first of the kind ever seen in Portugal.

In 1487, King John sent Pedro de Covillan and Alphonzo de Payva, both of whom could speak Arabic, to discover India by land.  They left Lisbon in the month of May, and took shipping in the same year at Naples for the island of Rhodes, and lodged there in the hotel of the Knights of St John of Jerusalem, belonging to Portugal.  From thence they went to Alexandria and Cairo, and then along with a caravan of Moors to the haven of Toro.  There they embarked on the Red Sea, and proceeded to Aden, where they separated; de Payva going into Ethiopia, while Covillan proceeded to India.  Covillan went to the cities of Cananor and Calicut, and thence to Goa, where he took shipping for Sofala, on the eastern coast of Africa.  He thence sailed to Mosambique, and the cities of Quiloa, Mombaza, and Melinda, returning back to Aden, where he and Payva had formerly separated.  Thence he proceeded to Cairo, where he hoped to have rejoined his companion; but he here learnt by letter from the king his master, that de Payva was dead, and he was farther enjoined by the king to travel into the country of Abyssinia[16] He returned therefore, from Cairo to Toro, and thence to Aden; and hearing of the fame of Ormuz, he proceeded along the coast of Arabia by Cape Razalgate to Ormuz.  Returning from the Gulf of Persia to the Red Sea, he passed over to the realm of the Abyssinians, which is commonly called the kingdom of Presbyter John, or Ethiopia, where he was detained till 1520, when the ambassador, Don Roderigo de Lima, arrived in that country.  This Pedro de Covillan was the first of the Portuguese who had ever visited the Indies and the adjacent seas and islands.

In the year 1490, the king sent Gonzalo de Sosa to Congo with three ships, carrying back with him the ambassador of the king of Congo, who had been brought over to Portugal in 1484, by Diego Caon.  During his residence in Portugal, this ambassador and others of his company had been instructed in the Christian religion, and baptized.  Gonzalo de Sosa died during the outward-bound voyage; and Ruy de Sosa, his nephew, was chosen to the command of the expedition in his stead.  Arriving in Congo, the king of that country received them with much joy, and soon yielded himself and the greater part of his subjects to be baptized; to the infinite satisfaction of the Portuguese, who by these means converted so many infidels from paganism to Christianity.