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The Triple Alliance

1428 – 1521

Not one empire but three cities sharing the tribute

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"The Aztec empire" is a name posterity gave it. Contemporaries knew an alliance between three cities on the lake in the Valley of Mexico, and it lasted ninety-three years.

The Triple Alliance

Tenochtitlan, Texcoco and Tlacopan joined in 1428 after overthrowing the city that had ruled them. They divided the spoils in fixed shares — two-fifths to each of the two largest, one-fifth to the smallest — and brought most of central Mexico under them within three generations.

Timeline

1325
Tenochtitlan is founded on an island in Lake Texcoco
1428
the Triple Alliance is formed
1440
Moctezuma I; expansion accelerates
1450
four years of drought and famine
1487
the Great Temple is dedicated
1502
Moctezuma II becomes ruler
1519
Cortés lands; the Tlaxcalans join him
1520
smallpox breaks out in the city
1521
Tenochtitlan falls after a 93-day siege

Tribute, not government

The alliance did not conquer in order to rule directly. Defeated cities kept their own rulers, their gods and their laws, and paid tribute in return: maize, beans, cotton cloth, feathers, cacao, jade, gold. A surviving tribute roll, the Codex Mendoza, records what came in from each province and how often.

That made the empire cheap to run and brittle to defend. No garrisons to speak of, no common administration — and every tributary city had reason to want out.

Why the city fell

Cortés had around five hundred Spaniards. What toppled Tenochtitlan was tens of thousands of Tlaxcalan and other allies who had been waiting for the opportunity, and a smallpox epidemic that ravaged the city for sixty days just before the decisive assault, carrying off its ruler.

To call it a Spanish conquest is to take the victors' word for it. It was a rising among the tributary cities, with Spanish weapons and Spanish leadership — and with a new disease setting the timing.

The city they found

Bernal Díaz, who was there, wrote that the soldiers asked one another whether what they saw was real. Tenochtitlan held around 200,000 people, larger than any city in Europe at the time. It had aqueducts of fresh water, streets swept daily, botanical gardens, and a market Cortés himself estimated at sixty thousand people a day.

It was levelled, and Mexico City was built on top.

For children

Three cities on the lake in the Valley of Mexico joined in an alliance and brought much of Mesoamerica under them. They conquered not to rule directly but to exact tribute — food, textiles, feathers and cacao flowed into Tenochtitlan.

Sources

  • Berdan, Aztec Archaeology and Ethnohistory (2014)
  • Restall, Seven Myths of the Spanish Conquest (2003)

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Part of Terra Saga — the story of Earth on a timeline. terrasaga.org · Last changed 2026-08-16