What actually happened
The conquest of the Aztec Empire was not the work of a few hundred Spaniards defeating a continent. The campaign of Hernan Cortes between 1519 and 1521 succeeded because it grew into a large war in which Indigenous allies supplied most of the fighters, an epidemic disrupted the capital, and political divisions inside the empire worked against Moctezuma II’s successors. The accounts that survive were written mostly by the Spanish, with some important Nahua testimony recorded afterward, and they should be read with that in mind.
Landing and alliances, 1519
Cortes sailed from Cuba in early 1519 with several hundred men and some horses, in defiance of the governor Diego Velazquez. After landing on the Gulf Coast he founded a town, Veracruz, and had himself named its leader, which gave his expedition a claim to legal independence. An Indigenous woman known as Malintzin, or Dona Marina, became his interpreter, working with a Spaniard, Geronimo de Aguilar. Her role was central to every negotiation that followed.
The road inland led through Tlaxcala, a confederation that had remained free of Aztec control. After a few hard battles in September 1519, the Tlaxcalans made peace and allied with the Spaniards, seeing a chance to defeat an old enemy. In October the Spaniards and their allies massacred many people at Cholula, a move that is generally described as a warning to others.
Entering Tenochtitlan
On 8 November 1519 Cortes and his men entered Tenochtitlan along a causeway and were received by Moctezuma. They were housed in the city, and within days the Spanish seized the ruler and held him in effect as a hostage. Reports that the Mexica believed Cortes to be a returning god are widely repeated, but modern historians consider them largely a later invention or exaggeration. Moctezuma probably acted for political reasons, balancing caution with hospitality.
In 1520 Cortes left to deal with a Spanish force sent by Velazquez under Panfilo de Narvaez, and defeated it, adding many men to his own army. In his absence Pedro de Alvarado, left in charge, ordered a massacre during the festival of Toxcatl in May. The city rose against the Spaniards.
The Noche Triste
When Cortes returned the Spaniards were besieged within the city. Moctezuma died in Spanish custody in June 1520; Spanish and Nahua accounts disagree about whether he was killed by his own people or by the Spanish. On the night of 30 June to 1 July the Spaniards tried to flee along the Tacuba causeway. Many were killed or captured, and much of the gold they carried was lost. The episode is remembered as the Noche Triste, the “sad night”.
Cortes and the survivors retreated to Tlaxcala, where the alliance held. Without these allies the Spanish expedition would very likely have ended there.
Smallpox
In late 1520 smallpox, a disease new to the Americas, spread through the Valley of Mexico. Epidemic outbreaks are well documented, and one of the victims was Cuitlahuac, who had succeeded Moctezuma as ruler and died after only a short reign. He was followed by Cuauhtemoc. Estimates of the death toll vary and are uncertain, but the epidemic was serious and disrupted leadership, food supplies and the ability to organise defence. Later outbreaks continued to hit Indigenous populations across the sixteenth century, and ancient DNA research has since been used to study some of them.
The siege, 1521
Cortes prepared carefully. At Tlaxcala his carpenters built thirteen brigantines, small sailing ships that were carried in pieces to Lake Texcoco and assembled there. Spanish accounts speak of very large Indigenous armies, in the tens of thousands, joining the campaign, among them the Tlaxcalans and people from Texcoco. Numbers are uncertain.
The siege began in the spring of 1521. The brigantines gave control of the lake, the aqueduct from Chapultepec was cut and the causeways were attacked one by one. Fighting in the city was fierce, house by house, and hunger and disease worsened conditions. Cuauhtemoc was captured in a canoe on 13 August 1521, and this date is used for the fall of Tenochtitlan. Much of the city was destroyed, and the Spanish later built Mexico City on its ruins.
Why the empire fell
- Many subject cities and rivals saw a chance to throw off Aztec tribute.
- Epidemic disease weakened the capital and its leadership.
- Indigenous allies far outnumbered the Spanish in the field.
- Steel weapons, horses and some firearms gave the Spanish real advantages, but not decisive ones alone.
The conquest was only the beginning of Spanish rule. Fighting continued for years in other regions, and the Spanish conquest of Yucatan against the Maya took decades, while in the Andes the later story of Pizarro and Atahualpa followed a similar pattern of alliances, disease and political division, though with its own details. Disease also moved ahead of the invaders: some scholars suggest an epidemic reached the Tawantinsuyu empire before Pizarro did, though the evidence is debated.
Nahua people have kept their own account of these events. The Florentine Codex records a version told from the Mexica side, and the descendants of the peoples involved live in Mexico today.