The Mexica Aztec Empire or the Triple Alliance (Nahuatl: Ēxcān Tlahtōlōyān, [ˈjéːʃkaːn̥ t͡ɬaʔtoːˈlóːjaːn̥]) began as an alliance of three Nahua ""altepetl"" city-states: Mexico-Tenochtitlan, Texcoco, and Tlacopan. These three city-states ruled the area in and around the Valley of Mexico from 1428 until they were defeated by the combined forces of the Spanish conquistadores and their native allies under Hernán Cortés in 1521.The Triple Alliance was formed from the victorious faction in a civil war fought between the city of Azcapotzalco and its former tributary provinces. Despite the initial conception of the empire as an alliance of three self-governed city-states, Tenochtitlan quickly established itself as the dominant partner militarily. By the time the Spanish arrived in 1520, the lands of the Alliance were effectively ruled from Tenochtitlan, and the other partners in the alliance had assumed subsidiary roles.The alliance waged wars of conquest and expanded rapidly after its formation. At its height, the alliance controlled most of central Mexico as well as some more distant territories within Mesoamerica such as the Xoconochco province, an Aztec exclave near the present-day Guatemalan border. Aztec rule has been described by scholars as ""hegemonic"" or ""indirect"". Rulers of conquered cities were left in power so long as they agreed to pay semi-annual tribute to the alliance as well as supplying military support for the Aztec war efforts. In return, the imperial authority offered protection and political stability as well as facilitating an integrated economic network of diverse lands and peoples with significant local autonomy despite their tributary status.