In 1580, Philip the Second, king of Spain, was crowned king of Portugal, thus widening an empire which remained so united until 1640. Pirates from enemy kingdoms attacked the commercial domains and routes of the Spanish Crown forcing it to strengthen its towns, villages and prosperous settlements in the overseas colonies.
In 1584, under the command of Philip the Second, Santo Amaro da Barra Grande Fortress was built in Santos Bay. It was designed by Giovanni Battista Antonelli, a military architect who accompanied the Spanish fleet led by Diogo Flores Valdez.

The fleet was made up of 16 caravels, and its mission was to patrol the New World's eastern coastline, going from the Equator to the Magellan Strait, strengthening it.