Tenochtitlan Falls After a 93-Day Siege
Smallpox, Tlaxcalan allies, and thirteen brigantines end the Aztec Empire and open the way for New Spain
Quick facts
- Siege began
- April 1521
- Spanish forces
- c. 700 infantry, 86 horses, 18 field guns
- Indigenous allies
- At least 100,000 Tlaxcalans and others
- Surrender
- 13 August 1521, Cuauhtemoc captured
What happened
Cortes began the siege of Tenochtitlan in April 1521 with roughly 700 infantry, 118 crossbowmen and harquebusiers, 86 horses, and 18 field guns, deploying thirteen purpose-built brigantines onto Lake Texcoco on 28 April to cut the city off. His decisive advantage was Tlaxcalan and other Indigenous allies, at least 100,000 strong, fighting alongside a Spanish force that was small by comparison. A smallpox epidemic in the preceding months had already killed much of the Aztec leadership and civilian population; the Spanish, for whom the disease had long been endemic, were largely unaffected. Spanish columns entered the city from three directions on 22 May, and after 93 days of fighting, starvation, and exhausted supplies, the last Aztec emperor Cuauhtemoc was captured trying to flee by canoe and surrendered on 13 August 1521. Tenochtitlan was sacked, looted, and its temples and monuments destroyed.
Why it matters
The fall of Tenochtitlan ended the Aztec Empire and gave Spain the city it would rebuild, on the same ruins and the same lake-bed foundations, as the capital of New Spain and eventually of modern Mexico. The scale of the human cost, a functioning capital of hundreds of thousands reduced by war, starvation, and epidemic disease within months, set the pattern for the demographic collapse that followed across the rest of the century.
How we know
Spanish military accounts detail troop numbers, the brigantine campaign, and the date of surrender; the smallpox epidemic's role is documented independently in both Spanish and Nahua sources describing mass death in the city before the final assault.
Sources
- World History Encyclopedia. The Fall of Tenochtitlan · Reputable sourceworldhistory.org · The domain "worldhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- Emerging Infectious Diseases, CDC. Megadrought and Megadeath in 16th Century Mexico · Peer-reviewed (author-declared)wwwnc.cdc.gov · Cited as a "journal" source (no stronger domain match).
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Related timelines
- The Aztec Empire → · The full siege, day by day, on the dedicated Aztec Empire timeline.
- The Age of Exploration → · See how the conquest of Mexico fit into Spain and Portugal's broader age of exploration and conquest.