The Mexica Empire: Tenochtitlan and the Triple Alliance

The Mexica, or Aztecs, were among the Chichimec peoples who migrated into the Valley of Mexico during the twelfth and thirteenth centuries CE, setting out, according to tradition, from a mythical place called Aztlán under the guidance of their patron god Huitzilopochtli. Arriving late and finding the valley already occupied by established lordships such as Culhuacán and Azcapotzalco, the Mexica endured a period of servitude before being expelled first from Chapultepec and later from Culhuacán. Tradition dates the founding of Tenochtitlan to 1325 CE, on a marshy islet in Lake Texcoco, at the spot where the migrants reportedly saw an eagle devouring a serpent while perched on a prickly pear cactus — an image later adopted as the founding emblem of Mexico itself. A splinter group soon founded the sister city of Tlatelolco nearby, and the lakeside site, initially a disadvantage for lack of dry land, was gradually transformed through chinampa farming into a natural fortress.