How Did Hernán Cortés Conquer the Aztec Empire?

Hernán Cortés conquered the Aztec Empire between 1519 and 1521, using a combination of military technology, political alliances with indigenous enemies of the Aztecs, bold and sometimes reckless personal leadership, strategic intelligence, and the catastrophic impact of European diseases on the densely populated city of Tenochtitlán. The conquest was not a single event but a campaign that lasted more than two years and that drew on Cortés’s exploitation of deep fractures within the Aztec state. For the full account of the Spanish conquest, see the cluster page Hernán Cortés, Francisco Pizarro, and the Conquest of the Americas.

The Forces at Cortés’s Disposal

Cortés’s expedition was modest by the standards of European warfare. He sailed from Cuba in February 1519 with about 11 ships, 500 Spanish soldiers, 16 horses, a few small cannon, and around 200 Cuban indigenous and African auxiliaries. He was the chief magistrate of the expedition, though he was acting without explicit royal authority, and he faced political rivals in Cuba. His force, however, was the largest single European expedition to have set foot in the Americas to that date, and it included men who had fought in the conquests of the Caribbean.

The Strategic Setting: A Fractured Aztec Empire

Cortés’s success depended on the political structure of central Mexico. The Aztec Empire, ruled by Montezuma II from Tenochtitlán, was not a unified state. It was a tribute empire, and many of the peoples it dominated, including the Tlaxcalteca, the Totonacs, and the Zapotecs, had been forced into the empire by military conquest and resented Aztec rule. The Tlaxcalteca, in particular, were a powerful state that had resisted Aztec conquest for over a century. They became Cortés’s most important allies, providing tens of thousands of warriors to the Spanish-led coalition. Cortés’s success depended as much on the politics of central Mexico as on his own military skills.

Stage 1: The March to Tenochtitlán, 1519

Cortés landed on the coast of Yucatán in March 1519, where he acquired a key ally, the indigenous woman known as La Malinche. La Malinche, a Nahua woman who had been enslaved by the Maya, had been given to Cortés shortly after his landing. She spoke both Maya and Nahuatl, and she became his interpreter, advisor, and intermediary with indigenous peoples throughout the campaign. Her role has been controversial ever since, and the Mexican Spanish word malinchista, meaning traitor, is derived from her name.

Cortés moved up the Gulf Coast, founding the city of Veracruz and establishing an alliance with the Totonacs, who were tributary to the Aztecs. He also took the critical decision of sinking his own ships, to prevent any thought of retreat. The Totonac alliance was followed by an even more important one: the Tlaxcalteca alliance, in which the Tlaxcalteca accepted Cortés as a potential ally against the Aztecs. In November 1519, Cortés entered Tenochtitlán, welcomed by Montezuma, and the Spanish were quartered in the palace of Axayacatl, Montezuma’s father.

Stage 2: The Capture of Montezuma, 1519–1520

Cortés’s decision to take Montezuma hostage was decisive. Rather than attack the Aztec state, he held the emperor captive, hoping to rule through him. The plan backfired when Cortés had to leave Tenochtitlán to deal with a rival Spanish expedition sent by the governor of Cuba. Cortés defeated the rival force, but during his absence, Pedro de Alvarado’s massacre of Aztec nobles in the Templo Mayor triggered a popular uprising. Montezuma was killed during the chaos, either by the Spanish or by his own people. On 30 June 1520, the Spanish were forced to retreat across the causeways of Lake Texcoco in what became known as the Noche Triste (Sad Night), a disaster in which the Spanish and their indigenous allies suffered heavy losses.

Stage 3: The Siege of Tenochtitlán, 1521

The siege of Tenochtitlán, beginning in May 1521, was the culminating campaign. Cortés had rebuilt his army with fresh Spanish forces, indigenous allies from Tlaxcala and other Mexican states, and thirteen small ships that had been built in sections on the coast and reassembled on Lake Texcoco. The siege lasted about 75 days. The Spanish and their allies cut off the city’s water and food supplies, used the new ships to control the lake, and gradually reduced the city block by block. The city was also suffering from a devastating smallpox epidemic, which had arrived with the Spanish and was spreading through the densely populated urban population. The Aztec emperor Cuauhtémoc, the last Aztec emperor, was captured in August 1521, and Tenochtitlán fell shortly afterward.

The Reasons for Cortés’s Success

Steel, Horses, and Gunpowder

European swords, pikes, and crossbows were more effective in close combat than the wooden macuahuitl clubs and spears of indigenous warriors. The Spanish also had steel armor, which indigenous weapons could not easily penetrate. Cannon and firearms added to the Spanish advantage, though the small numbers of firearms meant that they were not the central factor. The Spanish horses were decisive: domesticated horses had been extinct in the Americas for thousands of years, and indigenous warriors had no defenses against cavalry charges. The horses also provided a psychological shock, since the indigenous peoples had no word for them and often thought they were divine.

Indigenous Alliances

Cortés’s most important strategic decision was the alliance with the Tlaxcalteca. The Spanish were too few to conquer the Aztec Empire without indigenous support, and with tens of thousands of Tlaxcalteca and other indigenous allies, Cortés could sustain a long campaign against Tenochtitlán and besiege a city of perhaps 200,000 people. Many of the peoples who joined Cortés did so because they were enemies of the Aztec Empire and saw the Spanish as potential allies in their own political struggles.

Intelligence, Culture, and Disease

Cortés was unusually effective at gathering and using intelligence. La Malinche was critical, and Cortés also benefited from the political sophistication of the peoples he encountered. He understood the tribute structure of the Aztec Empire and the potential for indigenous rebellion. He was also a brilliant propagandist, presenting himself as the agent of the Spanish king, using religious imagery and ritual, and exploiting Aztec prophecies of returning gods. Perhaps the most important factor in the conquest was one that Cortés did not control: disease. Smallpox, measles, and influenza, brought by the Spanish, had been spreading through central Mexico since 1519. The Aztec state had no acquired immunity, and the densely populated Tenochtitlán was particularly vulnerable. The 1520 smallpox epidemic is to have killed Montezuma II, his successor Cuitláhuac, and a substantial fraction of the city’s population. The disease weakened the Aztec military and political system, making the Spanish-led coalition much more effective than it would have been against a healthy population, and it remains one of the most important elements of the demographic catastrophe of the Columbian Exchange.

What the Conquest Meant

The fall of Tenochtitlán in 1521 was the central event in the Spanish conquest of Mexico. Within a generation, the Aztec political system had been destroyed, the indigenous populations had been decimated, and Spanish colonial institutions had been established. The city of Mexico City was built on the ruins of Tenochtitlán and remains one of the largest cities in the world. The conquest also established the pattern of Spanish colonization in the Americas: a small European elite ruling over a much larger indigenous population, with the support of new Christian missions and a coercive labor system. The same pattern was followed in the conquest of the Inca Empire by Francisco Pizarro. The Spanish Empire, which lasted three centuries, was the direct institutional descendant of Cortés’s campaign.

Cortés in Historical Memory

Cortés has been one of the most contested figures in world history. In the 19th and early 20th centuries, he was celebrated as a civilizer and nation-builder, and statues were erected in many Mexican cities. Since the Mexican Revolution of 1910, the indigenous perspective on the conquest has been emphasized, and Cortés has been reevaluated as a violent conqueror. Statues have been removed, and the conquest has been reinterpreted in Mexican education and public culture. Modern historiography tends to emphasize the agency of indigenous peoples, the catastrophic costs of the conquest, and the role of disease, while still recognizing Cortés’s strategic brilliance. The conquest of the Aztec Empire is one of the central events of the Age of Exploration, and its consequences are still being worked out.