Bartolomeu Dias was a squire of the royal court, superintendent of the royal warehouses, and sailing-master of the man-of-war São Cristóvão (Saint Christopher). Very little is known of his early life. King John II of Portugal appointed him, on 10 October 1486, to head an expedition to sail around the southern tip of Africa in the hope of finding a trade route to India. Dias was also charged with searching for the lands ruled by Prester John, a fabled Christian priest and ruler of a territory somewhere beyond Europe.
He left 10 months later in August 1487. In the previous decades Portuguese mariners, most famously Prince Henry the Navigator (whose contribution was more as a patron and sponsor of voyages of discovery than as a sailor), had explored the areas of the Atlantic Ocean off Southern Europe and Western Africa as far as the Cape Verde Islands and modern day Sierra Leone, and had gained sufficient knowledge of oceanic shipping and wind patterns to enable subsequent voyages of greater distance. In the early 1480s Diogo Cão in two voyages (he died towards the end of the second) had explored the mouth of the Congo River and sailed south of the Equator to present-day Angola and Namibia