Sailing south down the African coast is easy. The wind and the current run that way. The difficulty, and the reason nobody had made a business of it, is the return.
The Portuguese solution took decades to work out and it is counterintuitive. Instead of beating back up the coast against the wind, you stand out into the open Atlantic, far from land, on a long arc to the north west, until you reach the latitude of the westerlies, and then run east for home. It requires nerve, because you are deliberately sailing away from your destination for weeks, and it requires the ability to know your latitude, which meant measuring the height of the sun or the pole star with a quadrant or a mariner's astrolabe and comparing it against tables.
The ship that made it practical was the caravel: small, shallow, with lateen sails that let it work closer to the wind than a square rigged vessel, and cheap enough to risk. Later voyages used bigger mixed rigs, square sails for running before the wind and lateen for handling.
None of this is a European invention out of nothing. The lateen sail, the astrolabe and much of the navigational mathematics came from the Mediterranean and the Islamic world, as chapter ten described. What was new was the systematic application, funded and recorded by a state, of a method for getting home from further away each time.
Not for spices at first, and not because the Ottomans had closed the routes, which they had not.
The first motive was gold. West African gold reached Europe across the Sahara, through a chain of Muslim intermediaries who took a margin at every stage. If you could reach the source by sea you cut all of them out. The Portuguese built a fortified trading post on the Gold Coast in 1482 for exactly this purpose, and it worked.
The second was slaves, and it started early. Portuguese ships were bringing enslaved Africans back from the 1440s, first as a raiding sideline and then as a purchase from established African merchants, and using them on the Atlantic islands to grow sugar. Madeira and then São Tomé became the model that was later transplanted across the ocean: a plantation island, a single export crop, and an enslaved workforce imported because the labour requirement was brutal and the mortality high.
Third, crusade, which was not decorative. Portuguese expansion began with the capture of a Moroccan port in 1415, papal grants authorised the enterprise in the language of holy war, and the hope of finding a Christian ally behind the Muslim world was a serious strategic objective for a century.
The spices came into focus later, once the shape of Africa became clear. A ship reached the southern tip in 1488, and in 1498 a fleet crossed the Indian Ocean with a local pilot and arrived at Calicut.
Not an empty sea. The Indian Ocean was the most sophisticated trading system in the world, with Gujarati, Arab, Persian, Malay, Chinese and East African merchants operating a network of ports, credit, shipping and law that had run for centuries.
The Portuguese arrived into it with goods nobody wanted. The presents offered at Calicut were reportedly laughed at. What they had that was distinctive was ships built to carry guns and to fight at sea, in an ocean where trade had been largely unarmed because there had been no state trying to control it.
So they took the one position available to them, which was force. Over the following two decades they seized key choke points, and operated a licensing system requiring other ships to buy a pass and call at Portuguese ports to pay duty, enforced by sinking those that did not. It was, in effect, a protection racket imposed on an existing economy.
It was also never dominant. Portuguese Asia was a chain of forts and factories with a few thousand Europeans, dependent on local allies and local finance, and Asian shipping continued in volume alongside it. What it did do was demonstrate that a European state could project armed force to the other side of the world and pay for it, and that lesson was learned by the Dutch and the English, who arrived a century later with joint stock companies and did it at scale.
Columbus was wrong. He believed the earth to be considerably smaller than it is and Asia to extend much further east, so that Japan lay a manageable distance west of the Canaries. The Portuguese experts who reviewed his proposal rejected it because their own estimates of the circumference were better, and they were right.
He was lucky rather than correct, and he never accepted what he had found. Four voyages later he was still describing the islands as the outskirts of Asia.
The immediate consequence was a diplomatic problem, solved in 1494 by a treaty dividing the unexplored world along a meridian in the Atlantic, Portuguese to the east and Castilian to the west. The line was drawn by two states, endorsed by a pope, and never accepted by anybody else.
Then the mainland conquests: a Spanish force took the Aztec capital in 1521, and another took the Inca empire in 1532. The question of how a few hundred men overturned states of millions has a mostly unglamorous answer.
Disease did most of it. Smallpox reached Mexico in 1520 and killed a large part of the population, including the ruler, during the campaign; a wave of epidemics ran ahead of the Spanish into the Andes and had already killed the Inca emperor and set off a civil war before Pizarro landed. Second, allies: the force that took the Aztec capital was overwhelmingly composed of indigenous troops from cities that hated the Aztec tribute system, and they were fighting their own war. Steel, horses and firearms mattered at the margin, in particular engagements, and they are not the explanation.
It is worth recording that the conquest was contested in Spain at the time, in public, by Spaniards, and that the arguments are on paper.
A Dominican friar preached a sermon in Hispaniola in 1511 asking the settlers by what right they held these people in servitude, and telling them they were in mortal sin. One of the men who heard it, Bartolomé de las Casas, was an encomienda holder who later gave up his own grant, became a friar, and spent fifty years documenting and denouncing what was being done, in books that are still among the main sources for the early Caribbean.
The crown responded with legislation, repeatedly. Laws of 1512 and 1542 restricted forced labour and forbade the enslavement of indigenous people. The settlers in Peru rose in armed revolt against the 1542 laws and the crown backed down on the central provisions. Law made in Madrid and enforced across an ocean by men whose income depended on ignoring it is not law in any strong sense.
In 1550 the emperor ordered a formal debate at Valladolid on whether the wars of conquest were just. Las Casas argued that the indigenous peoples were rational beings with legitimate rulers and property, that conversion must be peaceful, and that the wars were unlawful. His opponent argued from Aristotle that some peoples are natural slaves and are improved by subjection. No verdict was published.
Two things follow, and both matter. The idea that nobody knew any better is false; the arguments against were made at the time, by insiders, in the language of the conquerors' own law and religion. And they lost. Las Casas also, for a period, proposed importing African slaves instead to spare the indigenous population, and later repudiated it, which is worth stating because it shows how narrow even the humane position was.
The biological consequences were the largest, and they ran in both directions.
Out of the Americas came potatoes, maize, cassava, tomatoes, chillies, beans, squash, cacao, vanilla, tobacco and quinine. The potato and maize in particular raised the calorie output of European and Asian land significantly, and the population growth of the following two centuries is not explicable without them. The Irish, Chinese and African diets were all reshaped by American crops.
Into the Americas came wheat, rice, sugar, cattle, pigs, sheep, horses and the diseases. Smallpox, measles, influenza, typhus and later malaria and yellow fever entered populations with no prior exposure. Estimates of the resulting mortality vary widely and the field argues hard about the pre contact population, but the direction is not in dispute: a decline of somewhere between half and nine tenths across the century after contact, which is among the largest demographic catastrophes in recorded history. It was not planned, though it was frequently exploited, and in a few documented cases deliberately assisted.
The labour vacuum that resulted, combined with sugar, is what industrialised the Atlantic slave trade. The transatlantic voyage database compiled from surviving ships' records documents around twelve and a half million Africans embarked and about ten and a half million surviving the crossing over roughly four centuries. The plantation model of the Atlantic islands was applied to Brazil, the Caribbean and the North American mainland.
And the silver. Enormous deposits were found in the Andes in 1545 and in Mexico, worked by forced indigenous labour under lethal conditions. The output was so large that it raised prices across Europe for a century, funded Spanish wars including the ones in chapters twenty seven and twenty eight, and flowed to China, which was monetising its economy in silver and would take almost any quantity. For the first time there was a genuinely global circuit of exchange, and its hinge was a mountain in Bolivia.
Firm: the voyages, the treaties, the trading posts, the cargo records, and the slave trade database, which is built from customs records and ships' papers and is one of the most rigorous quantitative resources in history.
Firm: the crops and the silver flows.
Contested, seriously: pre contact American population. Estimates in the literature range from about eight million to over a hundred million for the hemisphere, and the mortality percentage depends entirely on which you start from. What is not contested is that whole societies ceased to exist.
Soft: the conquest narratives. Almost all our accounts are by the conquerors or by later writers using indigenous informants under colonial conditions, and the pattern of a handful of Europeans defeating an empire owes a good deal to men writing petitions for reward.
A myth to retire. Columbus did not prove the earth was round and nobody serious thought it was flat. Its rough size had been calculated in antiquity, medieval scholars taught it, and the argument against Columbus was that the distance was too great, which was correct. The story of a flat earth council opposing him was invented by an American novelist in 1828 and has been repeated ever since.
A framing to be careful with. Discovery, exploration and the New World are all words written from one side. The places were not new to the people living in them, and the encounter is better described as two previously separate networks being joined, extremely violently, by one of them.