From the formation of the Triple Alliance in 1428 the Mexica of Tenochtitlan and their allies conquered a tribute empire across central Mesoamerica, imposing tribute recorded in pictorial registers, installing governors and garrisons, and settling Nahua colonists in frontier provinces after the removal or destruction of local populations. Warfare was structured partly around the taking of captives: prisoners from campaigns and from the ritualised xochiyaoyotl or flower wars with Tlaxcala and Huexotzinco were sacrificed at the Templo Mayor and provincial temples. Sources on the scale of sacrifice are unreliable in a specific way: the dedication of the rebuilt Templo Mayor in 1487 is reported in colonial-era annals as involving 20,000 to 80,400 victims, figures modern scholars treat as ideological rather than countable, while excavation of the Huei Tzompantli skull rack beneath Mexico City from 2015 has recovered hundreds of skulls and confirms institutionalised display of sacrificial dead. The empire's structure — tribute, garrison colonies and captive-taking — is what the Spanish conquest of 1519-1521, already in the atlas, dismantled and partly reused.
The Triple Alliance of Tenochtitlan, Texcoco and Tlacopan subjugated city-states across central Mesoamerica, planted colonists in frontier provinces, and took war captives for sacrifice at the imperial temples
There is no census; the figure rests on modern reconstructions from early colonial tribute registers and archaeological settlement survey, and scholars differ by a factor of two or more. Sanders, Parsons and Santley put central Mexico at roughly 11-12 million in 1519, Whitmore's simulation at about 16 million, and Borah and Cook's much-criticised high count at 25 million; the Triple Alliance's directly tributary provinces held a subset of perhaps 5-6 million.
No defensible total can be given. Colonial-era annals report tens of thousands sacrificed at single dedications; these are rhetorical. Archaeology at the Huei Tzompantli establishes that sacrifice was institutionalised and repeated over decades but cannot yield an empire-wide rate. Deaths in the wars of conquest themselves were never recorded.
The Codex Mendoza and Matricula de Tributos record tribute and labour obligations, and excavation of the Huei Tzompantli by Mexico's INAH documents institutionalised sacrificial killing.
Mexico