Portuguese attempts at Monopoly on the Upper Guinea Coast, 1580–1650

Between 1580 and 1640 the union of the Spanish and Portuguese crowns strengthened the commercial partnership which previously existed with respect to the supply of Guinea slaves to the Spanish Indies. The conduct of the slave trade on the Upper Guinea Coast involved the active participation of the African chiefs, as well as the services of a considerable number of resident Portuguese traders, known as lançados. Before 1640, while Iberian unity prevailed, the main source of discord in the area lay in the fact that the Spanish slave ships, with the help of the lançados and the chiefs, were able to disregard the regulation that all ships loading slaves on the Upper Guinea Coast should pay duties at Santiago (Cape Verde islands), which the Portuguese used as the hub of their administration. After 1640 the restored Portuguese monarch attempted to exclude Spain from the commerce of the Upper Guinea Coast, and in the process, alienated the lançados and the African chiefs.