An alliance born from civil war
The Aztec Empire emerged from the Triple Alliance formed around 1428 to 1430 between the city-states of Tenochtitlan, Texcoco and Tlacopan, following a civil war that broke out after the death of the dominant regional Tepanec king in 1426. Under rulers including Itzcoatl and later Moctezuma I and Ahuitzotl, the alliance expanded steadily between 1440 and 1502, eventually controlling much of central Mexico and reaching both the Gulf of Mexico and the Pacific coast by the early sixteenth century. The empire’s history ended abruptly with the Spanish conquest, a campaign led by Hernán Cortés that ran from his 1519 arrival to the fall of Tenochtitlan on 13 August 1521.
A history possibly burned by its own ruler
Reconstructing the empire’s history is complicated by a significant gap in its own surviving records: it has been alleged that Tlacaelel, an administrative officer who served across several reigns, ordered the burning of most existing Aztec books for political reasons, which would mean much of the empire’s own contemporaneous self-documentation simply does not survive. What remains includes pictographic codices such as the Codex Mendoza and Codex Boturini, compiled partly after the conquest, Spanish accounts including those of the conquistador Bernal Díaz del Castillo, and archaeological evidence from sites such as the Templo Mayor in modern Mexico City, together forming a record built substantially by outsiders and by later reconstruction rather than by the empire’s own contemporary voice.
Expansion under a handful of kings
The empire’s expansion rested on a tribute system extracted from conquered city-states across central Mexico, a structure that generated considerable resentment among subject populations, resentment that would later prove decisive when Cortés arrived. Groups such as the Tlaxcaltecs and Totonacs, long weary of Aztec dominance, allied with the Spanish rather than with fellow Mesoamerican peoples, a choice that reflected pre-existing regional grievances rather than any inherent Spanish appeal, and which gave Cortés a far larger indigenous force than his roughly several hundred Spanish soldiers alone could have provided, without which the campaign against Tenochtitlan’s much larger population would have been considerably harder to sustain.
A ruler’s cooperation still disputed
A central and still unresolved dispute concerns Moctezuma II’s own conduct during the initial Spanish contact: historians disagree over whether he cooperated with Cortés willingly, perhaps out of political calculation, or was effectively held prisoner and coerced, with the available Spanish and indigenous sources offering conflicting impressions that have not been reconciled. A related debate concerns how much credit for the conquest’s outcome belongs to European military technology, including cavalry described by some historians as decisive, against the role of smallpox, which devastated the population independently of any battle, and against the sheer scale of indigenous alliance defection working against the Aztec state from within.
Allies as decisive as weapons
The empire’s fall came only after a serious Spanish setback: a 1520 massacre of Aztec nobles by a subordinate commander triggered an uprising that forced a catastrophic Spanish retreat, remembered as the Night of Sorrows, in which roughly a thousand Spaniards and a similar number of indigenous allies died. Cortés returned with reinforcements, including brigantines that gave him control of the lake surrounding Tenochtitlan, and a three-month siege ended with the city’s fall in August 1521. Smallpox, introduced with the Spanish, caused catastrophic mortality across the wider population independently of the fighting, with estimates for disease deaths across the region running into the millions.
A city that became another city
This is a genuinely rewarding subject because it forces you to reckon with how much of the historical record was shaped by the conquerors and by the empire’s own possible self-erasure of records, rather than by any neutral contemporary account. It rewards attention for the tribute system and alliance politics that made the conquest possible as much as for the conquest itself. It leaves the question of Moctezuma’s own agency genuinely open rather than resolved, which will frustrate readers wanting a clear verdict on his choices. That open verdict is arguably more honest than a confident answer would be, given how thoroughly the surviving sources on both sides were shaped by their authors’ own competing interests.