European voyages around the Cape of Good Hope and across the Atlantic brought revolutionary changes in world history, but the full consequences were slow to appear. European shipping, like other European technology, had developed remarkably during the Middle Ages, but it was not yet vastly superior to Asian shipping. It was not yet what it was to become when industrial power made Europe the unquestioned world leader. Europeans of the sixteenth century were much stronger than they had been in military and naval power, but they were not dominant.

The European “maritime revolution” of the fifteenth and sixteenth centuries was not so much a revolution in ship design as the discovery of the world wind system. Prevailing winds vary with latitude in the Atlantic, Pacific, and the southern Indian Ocean. Strong and regular trade winds blow from the east over about twenty degrees north and south of the equator – from the northeast north of the line, from the southeast south of the line. Still farther north or south, from about forty to sixty degrees north or south, the prevailing winds are from the west. By the middle of the fifteenth century, Portuguese mariners had discovered this pattern off the Saharan coast of Africa. They learned to sail south with the northeast trades and then, on the return, to make a long tack to the north-northwest sailing as close as they could to the prevailing northeasterly winds. In time, this would bring them to the westerlies in the vicinity of the Azores. Columbus had sailed down the African coast before he considered crossing the Atlantic.