This is a history of one of the best known peoples of pre-Columbian America. The Aztecs were the upstarts of Meso-America. Until the thirteenth century they were a little-known people practising subsistence agriculture in the north of what is now Mexico. At that time they migrated to the Valley of Mexico, and having first learnt military arts by hiring themselves as mercenaries to the Oaxacans and other established societies, promptly used these skills to subjugate their former masters, and to swallow up a succession of Meso-American kingdoms. By the time Cortes arrived they were the undisputed rulers of a large empire, which they kept subdued by regular human sacrifice and whose people they taxed to the bone (factors used by Cortes to foment rebellion).