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13 August 1521Primary source · 2 sourcesEstimated

Smallpox and War Destroy Tenochtitlan

A disease that arrived with the Spanish kills faster than either side's soldiers, and the Aztec Empire does not survive it

On the timeline · around 13 August 1521 · Conquest and CircumnavigationConquest and CircumnavigationA Connected WorldSmallpox and War Destroy Tenochtitlan15201525153015351540

Quick facts

Disease
Smallpox
Fall of Tenochtitlan
13 August 1521
Estimated pre-contact population (Valley of Mexico)
15-20 million (disputed)
Estimated population a century later
2-3 million (disputed)

What happened

During the war between Cortes's forces and the Aztec Empire, a smallpox epidemic swept through the Valley of Mexico, likely carried by a member of a Spanish resupply expedition, and spread through a population with no prior exposure to the disease. The epidemic hit while Tenochtitlan was already under siege and killed the emperor Cuitlahuac along with an estimated third to half of the population in the hardest-hit areas. Tenochtitlan fell to Spanish and allied forces on 13 August 1521, two years after Cortes's arrival. Estimates of the pre-contact population of the Valley of Mexico run from 15 to 20 million; within a century the same region held perhaps two to three million people, according to most historians' estimates, though exact figures remain disputed given the limits of the surviving records.

Why it matters

The combination of siege warfare and epidemic disease that destroyed the Aztec Empire became the template for Spanish conquest across the Americas: European disease weakened populations faster and more thoroughly than European weapons did, and the two often arrived together. Historians still debate the surviving population figures because Spanish record-keeping in the decades right after conquest was inconsistent.

How we know

The Mariners' Museum's entry on Cortes states plainly that Spanish diseases, especially smallpox, wiped out much of the native population alongside enslavement; broader population estimates for the Valley of Mexico's decline are treated as approximate by historians because of gaps and inconsistencies in the surviving Spanish census records.

Sources

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