Triple Alianza (México)

In 1428, the city-states of Tenochtitlan, Texcoco, and Tlacopan joined forces to defeat Azcapotzalco, until then the dominant power in the Valley of Mexico, and sealed the Triple Alliance. That alliance became the core of what is commonly called the Aztec Empire, with tribute from conquered regions flowing to the three capitals.

Over time Tenochtitlan became the dominant partner, a position it held until the Spanish conquest of 1521.