Henry was 21 when he and his father and brothers captured the Moorish port of Ceuta in northern Morocco. Ceuta had long been a base for Barbary pirates who raided the Portuguese coast, depopulating villages by capturing their inhabitants to be sold in the African slave trade. Following this success, Henry began to explore the coast of Africa, most of which was unknown to Europeans. His objectives included finding the source of the West African gold trade and the legendary Christian kingdom of Prester John, and stopping the pirate attacks on the Portuguese coast.