Repercussions

Smallpox, measles, typhus, and influenza entered populations with no acquired immunity and killed on a scale without parallel in recorded history. Smallpox reached Tenochtitlan in 1520 with Narváez's men and ran ahead of the Spanish everywhere afterward — it had already killed the Inca emperor Huayna Capac and triggered the civil war before Pizarro ever set foot in Peru. Estimates for the indigenous population decline of the Americas over the following century run from 50% to 90%. The demographic catastrophe was the single most consequential outcome of the conquest and no one intended it. It emptied the land the Spanish then claimed was empty, destroyed the labour base the encomienda depended on, and drove the transatlantic slave trade that replaced it.

In fourteen years the two largest states in the Americas ceased to exist. Tenochtitlan — one of the world's great cities, with perhaps 200,000 inhabitants — was razed and Mexico City built on its rubble. Cuzco was looted and its temples stripped. The Aztec Triple Alliance ended outright in 1521; the Inca state fragmented in 1533 and its last redoubt at Vilcabamba held out until 1572. Two independent civilisations with their own writing, astronomy, engineering, and statecraft were destroyed as functioning polities within a single generation, and their institutions were replaced wholesale by a viceregal system ruled from Madrid.

The silver mountain at Potosí, found in 1545, and the mines at Zacatecas poured bullion into Spain on a scale that reshaped world trade. Much of it did not stay in Europe: the Manila galleons carried American silver directly across the Pacific to China, whose economy had monetised in silver, creating the first genuinely global trade circuit. It also fuelled a century of price inflation across Europe. American silver financed the Habsburg wars, connected Asia and Europe through the Americas for the first time, and left Spain itself hollowed out — the bullion passed through, paying for imports and armies rather than industry.

The conquest permanently connected two biological worlds that had been separate since the last ice age. Maize, potatoes, tomatoes, cacao, chillies, vanilla, and tobacco went east; wheat, sugar, cattle, pigs, sheep, horses — and the diseases — came west. The potato alone would reshape the demography of northern Europe, and the horse would remake the culture of the North American plains. Arguably the largest ecological event since the end of the Pleistocene. It underwrote European population growth for centuries, and there is no Italian cuisine without tomatoes, no Irish history without potatoes, and no Plains horse culture without Spanish strays.

The conquistadors were rewarded with encomiendas — grants of indigenous labour and tribute — that amounted to slavery in all but name. In Peru the Spanish adapted the Inca labour draft into the mita, which conscripted men from across the highlands to work Potosí. Mortality in the mines and the mercury works at Huancavelica was appalling, and whole communities fled or were destroyed by the levy. The mita's economic geography is still measurable: districts subject to the draft remain measurably poorer today than neighbouring districts that were not, four centuries later.

The conquest produced a new population almost immediately. Cortés's son by La Malinche, Martín, was among the first of millions. Over centuries a stratified caste system — peninsulares, criollos, mestizos, indigenous, and enslaved Africans — sorted colonial society by ancestry, but the boundaries blurred constantly, and Spanish, Nahuatl, Quechua, and Aymara mixed alongside the people. Modern Latin America — its languages, its religion, its cuisine, its populations — is the direct product of this fusion, and Spanish became one of the most widely spoken languages on earth.

The scale of the killing produced Europe's first sustained argument about the rights of conquered peoples. Bartolomé de las Casas, a former encomendero turned Dominican, documented the atrocities in his 'Short Account of the Destruction of the Indies' and argued at Valladolid in 1550–51 against Juan Ginés de Sepúlveda, who held that the indigenous were natural slaves. The New Laws of 1542 tried, largely unsuccessfully, to curb the encomienda. The debate is a founding moment in the history of international law and human rights — the first time a European power formally argued with itself about whether conquest was legitimate. It also fed the 'Black Legend,' Protestant Europe's propaganda image of uniquely Spanish cruelty.

Spanish clergy systematically destroyed indigenous books as idolatrous. Bishop Diego de Landa's auto-da-fé at Maní in 1562 burned the Maya libraries; of the thousands of Maya codices that existed, four survive. Aztec pictorial manuscripts fared little better. Temples were demolished and churches built from their stones, often on the same platforms. The written record of two literate civilisations was almost entirely erased, and much of what is known about them now comes from archaeology or from post-conquest texts written under Spanish supervision — including, ironically, Landa's own account of what he destroyed.

The conquest established a repeatable method: land a small force, find the local enemies of the local power, arm them, decapitate the leadership, and rule through a compliant successor. Cortés's and Pizarro's campaigns were studied and imitated for centuries, and the conquistadors themselves fanned out to apply them — Alvarado to Guatemala, de Soto to Florida, Valdivia to Chile. Divide-and-rule via indigenous allies became the standard operating procedure of European colonialism from India to Africa. Almost no empire was ever built by Europeans alone; nearly all were built with local allies who expected to be partners and became subjects.

Spain became the first empire on which the sun never set, holding territory from California to Tierra del Fuego and across the Pacific to Manila. But the indigenous labour force it had counted on was collapsing from disease, and the plantations and mines needed workers. The crown turned to the Atlantic slave trade, and Spanish America imported enslaved Africans in enormous numbers from the sixteenth century onward. The demographic void left by the epidemics was filled with enslaved Africans — the conquest of the Americas and the Atlantic slave trade are not two separate histories but one causal chain, and their consequences are still being litigated across the hemisphere.