The fifteenth century brought about profound changes in that it shaped the history of the world over the next three hundred years. European attitudes were shaped by the Reconquista, a long struggle to rid the Iberian Peninsula of Muslims. Centuries of Christian–Muslim conflict had led to an abhorrence of Muslims as infidels and other religions as heretical, pagan, and barbarian. Meanwhile Europe was on a path to invincible sea power. The development of the caravel with its V-hull and moveable sails opened up the open ocean for exploration, even into the wind through the sailing strategy of tacking. The leader in understanding the possibilities of this new power was the Portuguese Henrique (1394–1460) whose interest in geography and his commissioning of mapmakers led to his reputation as the “Navigator,” though this description came centuries later, and Henry himself never went to sea.

Henry brought an expansive imagination and the caravel together to promote Portuguese expansion beyond Europe. In his lifetime this tiny European nation took control of the Azores and a string of outposts down the coast of Africa. Inspiring vistas opened up. Following Henry's death, the Portuguese sent out successive expeditions south along the African coast, each one pushing farther south until an expedition rounding of the Cape of Good Hope in 1497 and founded a colony at Goa on the coast of India. Meanwhile the Italian-born Christopher Columbus, inspired by visions of Cathay (China), Capango (Japan), and India from The Travels of Marco Polo, dreamed of sailing west to reach the East. After a campaign of persuasion with the Spanish monarchs, King Ferdinand and Queen Isabella, he was outfitted with three ships that took him to a landing in the Americas in 1492.

An issue emerged with Portuguese landings on the coast of Africa that brought them into conflict with the Saracens, the regional name for Muslims. Without hesitation in 1452 Pope Nicholas V issued a papal bull, Dum Diversas (Until Different), that conferred authority on the Portuguese king, Alfonso V, to subdue and conquer the Saracens.