A serious son of an equally studious and serious mother, Henry's curiosity regarding seafaring matters was most likely developed whilst as a child growing up close to the Douro riverside in Porto. What motivated Henry is a matter of conjecture but expeditions were still very much bound up with the Crusades. Interest in voyages of discovery were fuelled by talk of the legendary Christian Kingdom of Prester John, and its untold riches, said to lie somewhere in Africa. Conquering Moorish lands in North Africa was a prerequisite to gaining access into the hinterland of that continent; the seeds had been sown to think of wider possibilites.

With a fleet of 200 ships, the building of which Henry himself supervised, he set sail from Porto with his father and brother on a Crusade against Ceuta in North Africa where they won a resounding victory. A lasting impression on Henry was not so much the victory itself but the oriental riches they looted. What of these lands from where such a wealth of gold, silver, silks and spices originated? Henry returned to Portugal a thoughful man but his energies were still channelled into taming the north coast of Africa. Only later, on hearing tales from other sailors, was Henry drawn into the search further afield although he himself remained a landlubber after his foray to north Africa.

Taking himself off down to the untamed wilderness of Sagres in Algarve, Henry established an observatory and school of navigation, where he devoted time, effort and money into improving navigational aids and boat design. Using revenue from his position as Duke of Viseu, Governor of the Algarve and also Governor of the Order of Christ, he gathered together experts in astronomy and astrology, cartography and geography as well as knowledgeable mariners. His shipyard at Lagos built the boats, from where they set sail; the red Cross of Christ emblem of the Order of Christ prominently displayed on their white sails. Trading gradually took over precedence from crusading as Henry developed a tidy business from financing and equipping excursions down the west coast of Africa.

A huge leap forward came in the form of a new boat, the caravel, which Henry and his team designed and perfected. The caravels light weight gave it manoeuverability and speed and a shallow draught the ability to sail close inshore. Another advantage was the need for a smaller crew and thus more storage space for goods.

Under Henry's patronage Gil Eanes finally passed Cape Bojador on Africa's west coast in 1434, a barrier beyond which fifteen earlier expeditions had been too afraid to penetrate. Explorers were encouraged to set up trading posts at each new landing place, where they erected stone pillars (padrðes) topped by crosses and engraved with the Portuguese coat of arms. They also brought back samples of plant life, fruit and nuts. It was to be a further decade before Gil Eanes returned with the first human cargo of African slaves, which prompted an escalation of trade along the west coast of Africa.