The Aztec Triple Alliance, or Aztec Empire began as an alliance of three Nahua city-states or "altepeme

Altepetl

The altepetl, in Pre-Columbian and Spanish conquest-era Aztec society, was the local, ethnically based political entity. The word is a combination of the Nahuatl words ā-tl, meaning water, and tepē-tl, meaning mountain....

": Tenochtitlan, Texcoco, and Tlacopan

Tlacopan

Tlacopan , also called Tacuba, was a Pre-Columbian Mesoamerican city-state situated on the western shore of Lake Texcoco.Founded by Tlacomatzin, Tlacopan was a Tepanec kingdom subordinate to nearby Azcapotzalco...

. These city-states ruled the area in and around the Valley of Mexico

Valley of Mexico

The Valley of Mexico is a highlands plateau in central Mexico roughly coterminous with the present-day Distrito Federal and the eastern half of the State of Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several pre-Columbian civilizations, including...

 from 1428 until they were defeated by the Spanish conquistador

Conquistador

Conquistadors were Spanish soldiers, explorers, and adventurers who brought much of the Americas under the control of Spain in the 15th to 16th centuries, following Europe's discovery of the New World by Christopher Columbus in 1492...

es and their native allies under Hernán Cortés

Hernán Cortés

Hernán Cortés de Monroy y Pizarro, 1st Marquis of the Valley of Oaxaca was a Spanish Conquistador who led an expedition that caused the fall of the Aztec Empire and brought large portions of mainland Mexico under the rule of the King of Castile in the early 16th century...

 in 1521.

The Triple Alliance was formed from the victorious faction in a war between the city of Azcapotzalco

Azcapotzalco (altepetl)

Azcapotzalco was a pre-Columbian Nahua altepetl , capital of the Tepanec empire, in the Valley of Mexico, on the western shore of Lake Texcoco.The name Azcapotzalco means "at the anthill" in Nahuatl...

 and its former tributary provinces.