In the 15th century, the Portuguese explored the sea route to India and Pope Nicholas V enacted the Papal bull Romanus Pontifex. This bull granted the patronage of the propagation of the Christian faith in Asia to the Portuguese (see "Padroado") and rewarded them with a trade monopoly for newly discovered areas. After Vasco da Gama arrived at Calicut on the coast of Kerala in India in 1498, the trade became prosperous. In 1510, the Portuguese wrested Goa from the Sultan of Bijapur and finally established themselves in Goa. By 1544, they conquered the districts of Bardez and Salcette in Goa. The initial converts were the native Goan women who married the Portuguese men that had arrived with Afonso de Albuquerque during the Portuguese conquest of Goa.