Why Europeans sailed: motives for the voyages of discovery
Europe on the Eve of Exploration
In the late fifteenth century, European merchants were hungry for the spices of Asia — pepper, cinnamon, nutmeg and cloves. These goods were not luxuries; they preserved food, masked the taste of spoiled meat and were worth their weight in silver. The problem was distance. Overland routes to Asia ran through the heart of the Ottoman Empire, whose sultans taxed or disrupted Christian merchants at will. The fall of Constantinople in 1453 intensified the pressure to find an alternative route.
The fall of Constantinople to the Ottoman Turks in 1453 blocked reliable overland trade to Asia and gave Spain and Portugal a powerful economic motive to find sea routes instead.
The Rivalry Between Spain and Portugal
By the 1480s, two Iberian kingdoms had emerged as the dominant maritime powers. Portugal had been exploring the African coast since the 1420s under the guidance of Prince Henry the Navigator (1394–1460), who sponsored systematic voyages down the African coast. Castile (soon united with Aragon to form Spain under Ferdinand and Isabella) was a latecomer but equally determined to find its own route to Asia. This rivalry shaped the age of exploration.
In 1494, the two powers signed the Treaty of Tordesillas. An imaginary north–south line was drawn through the Atlantic, roughly 370 leagues west of the Cape Verde Islands. Portugal was allocated territory to the east of the line (giving it access to Africa and Asia); Spain was allocated territory to the west (opening the Americas). The treaty formalised a partnership in colonialism that would define the next century.
Prince Henry never sailed on the voyages he sponsored, but he transformed Portugal into a maritime power. He established a school of navigation at Sagres (or near it — the exact location is debated), attracted astronomers, cartographers and pilots, and commissioned systematic voyages along the African coastline. By the time he died in 1460, Portuguese sailors had reached as far south as Sierra Leone. His initiative gave Portugal a head start of several decades over its rivals.
The Portuguese motivation was partly commercial (finding a direct sea route to the spice markets of India and the East Indies), partly religious (spreading Christianity and countering Islam along the African coast) and partly strategic (finding Prester John — a legendary Christian king in Africa whose alliance might outflank the Ottoman Empire). These three drivers — gold, God and glory — ran through virtually every European voyage of discovery.
The Reconquista and Religious Motivation
Spain’s rulers had just completed the Reconquista — the 700-year struggle to reclaim the Iberian Peninsula from Muslim rule — in January 1492 when Granada fell. The same year, Ferdinand and Isabella expelled Jews from Spain and funded Columbus’s first voyage. This was not coincidence: the Catholic monarchs saw exploration as a continuation of their crusading mission. Spreading Christianity to new peoples was a genuine motive alongside economic gain, and it would powerfully shape how conquistadors justified what they did to indigenous populations.
Historians summarise the motives for exploration as “Gold, God and Glory”: the search for profitable trade routes, the spread of Christianity and the desire for personal fame and royal prestige.
Technological Advances
Without new technology, long ocean voyages would have been impossible. Three innovations were especially important. The caravel was a new type of ship that combined a sturdy hull for ocean conditions with lateen sails that allowed it to sail closer to the wind. Unlike traditional square-rigged vessels, the caravel could make progress even when the wind was unfavourable, making return journeys along the African coast possible for the first time.
Navigation also improved dramatically. The magnetic compass allowed sailors to maintain a bearing even when stars were hidden. The astrolabe allowed navigators to calculate their latitude by measuring the angle of the sun or Pole Star above the horizon. Together, these tools gave pilots enough confidence to leave sight of land and venture into the open Atlantic.
The astrolabe measured the angle of the sun at noon or the Pole Star at night. Because the sun’s angle above the horizon changes predictably with latitude, a navigator could compare their reading against published tables to calculate how far north or south of the equator they were. Longitude — east–west position — remained impossible to calculate accurately until the eighteenth century. Sailors in the 1490s navigated by dead reckoning: combining their known starting point, estimated speed and compass bearing to guess their position. It was imprecise, but combined with the astrolabe it was enough to cross an ocean.
Improved cartography also mattered. The rediscovery of Ptolemy’s Geography in the early fifteenth century gave European cartographers a framework for world maps. Arab and Chinese geographical knowledge was absorbed by Iberian scholars. By 1480, educated Europeans understood that the Earth was a sphere — the question was not whether a westward route to Asia was theoretically possible, but whether it was practically achievable. Columbus believed the distance was shorter than it actually was, a miscalculation that accidentally led him to the Americas.
The Route to Asia: South-East or South-West?
Portugal pursued the south-eastern route: sailing south along Africa, rounding the Cape of Good Hope and crossing the Indian Ocean to reach India. This strategy paid off in 1497–1499 when Vasco da Gama reached Calicut. Spain, blocked from this route by the Treaty of Tordesillas, had to look south-west. Columbus argued that Asia could be reached by sailing west across the Atlantic — a proposition that most informed sailors thought was wrong, not because they believed the Earth was flat, but because they knew the ocean was too wide to cross. Columbus was right that a westward route existed; he was wrong about what lay at the end of it.