The Portuguese prince Henry the Navigator (1394-1460) launched the first great European voyages of exploration. He sought new lands and sources of revenue for his kingdom and dynasty and searched for eastern Christian allies against Islam.

Born at Oporto on March 4, 1394, Henry was the third son of John I of Portugal and Philippa of Lancaster. He grew to maturity at a time when John I was bringing to a close a confused period of civil strife and war with Castile and securing Portugal's independence. The conflicts of this period had left the nobility decimated and impoverished and the monarchy's revenues greatly depreciated. Thus the ruling families began to look abroad for new worlds of wealth, land, and honors to conquer.

John and his sons became involved in a threefold movement of Portuguese expansion, comprising the campaign to conquer Moorish North Africa; the movement to explore and conquer the...