Itzcoatl was the natural son of tlàtoāni Acamapichtli and an unknown Tepanec woman from Azcapotzalco. He was elected as the king when his predecessor, his nephew Chimalpopoca, was killed by Maxtla of the nearby Tepanec āltepētl (city-state) of Azcapotzalco. Allying with Nezahualcoyotl of Texcoco, Itzcoatl went on to defeat Maxtla and end the Tepanec domination of central Mexico. After this victory, Itzcoatl, Nezahualcoyotl, and Totoquilhuaztli, king of Tlacopan, forged what would become known as the Aztec Triple Alliance, forming the basis of the eventual Aztec Empire.