John III (John the Fortunate), 1502–57, king of Portugal (1521–57), son of Manuel I. His reign saw the Portuguese empire at its apogee. The great Asian possessions were extended by further conquest, and systematic colonization of Brazil was begun. However, in Portugal itself decadence had set in with the decline of both agriculture and the population. Portugal's African exploits were abandoned, but many black slaves were brought into the country. The Inquisition was introduced (1536) by John, who was devoted to the clerical party. The court was corrupt, though the king was not. Literature flourished early in his reign, but Portugal was falling into the stagnation that characterized the disastrous reign of Sebastian, who succeeded him.