Fall of Tenochtitlan (1521): Siege of the Aztec Capital

The fall of Tenochtitlan in 1521 ended the Spanish conquest of the Aztec capital after a siege of about 75 days. Hernán Cortés, a few hundred Spaniards and tens of thousands of Indigenous allies blockaded the island city in Lake Texcoco, fought their way along its causeways and destroyed it street by street. On 13 August 1521 the last ruler, Cuauhtémoc, was captured, and on the ruins the Spaniards built Mexico City.

Background: the road to the siege

Tenochtitlan, founded on an island in Lake Texcoco in the 14th century, had grown into one of the largest cities in the world, with perhaps 150,000 to 200,000 inhabitants or more. Linked to the shore by causeways and supplied with fresh water by an aqueduct from Chapultepec, it was the capital of the Mexica and the dominant power of the Triple Alliance that ruled much of central Mexico.

Cortés had entered the city in November 1519 as a guest of Moctezuma II, then held him captive. After Pedro de Alvarado’s massacre of nobles at the festival of Toxcatl in May 1520, the city rose. Moctezuma died, and on the night of 30 June 1520 the Spaniards fled with heavy losses in the episode known as La Noche Triste. They survived a further attack at the Battle of Otumba and took refuge in Tlaxcala.

During the following months, smallpox, brought from the Caribbean with Spanish reinforcements, spread through central Mexico. It killed many thousands, including the new ruler Cuitláhuac, who died in late 1520 after only about 80 days in power. His cousin Cuauhtémoc, a young noble in his early twenties, became ruler early in 1521.

Preparing the siege

Cortés concluded that Tenochtitlan could only be taken if he controlled the lake. On his orders the shipwright Martín López built 13 brigantines, small sailing and rowing vessels each able to carry a gun and a couple of dozen men. They were built in Tlaxcala, then carried in pieces across the mountains by thousands of Tlaxcalan porters and reassembled at Texcoco on the eastern shore.

Texcoco had changed sides. A succession dispute in its ruling family brought to power Ixtlilxóchitl, a rival of the Mexica, who allied with Cortés and supplied large numbers of warriors. During the early months of 1521 Cortés’s forces also campaigned around the lakes, subduing or winning over towns such as Chalco, Xochimilco and Iztapalapa and isolating the capital.

A canal was dug to bring the brigantines to the lake, and they were launched on 28 April 1521. Cortés’s own count of his Spanish force was about 900 men, including 86 horsemen and around 118 crossbowmen and arquebusiers, with three heavy guns and 15 small field pieces. The allied Indigenous troops numbered in the tens of thousands, and Spanish sources claimed well over 100,000; whatever the exact figure, they made up the overwhelming majority of the besiegers.

The siege

In May 1521 Cortés divided his land forces into three divisions. Pedro de Alvarado took the western causeway at Tlacopan (Tacuba), Cristóbal de Olid the southern approach at Coyoacán, and Gonzalo de Sandoval the southeastern route from Iztapalapa. Late in May the besiegers broke the aqueduct from Chapultepec, cutting off the city’s main supply of fresh water. Cortés himself took command of the brigantines, which soon swept the Mexica war canoes from the open lake.

The Mexica defended themselves skilfully. They dug gaps in the causeways and hid stakes in the water to trap the brigantines. By night they rebuilt barricades that the attackers had cleared by day. Warriors fought from canoes, rooftops and canals, and tried to capture Spaniards alive.

At first Cortés hoped to take the city without destroying it, but each day’s gains were lost again at night. On 30 June 1521 a major assault failed when the attackers were caught at a breach in a causeway. Cortés was nearly captured, and dozens of Spaniards were taken alive. Bernal Díaz recorded that the besiegers could see their captured comrades being sacrificed on the temple platforms. Some allied contingents left for a time, believing the Spaniards were beaten.

Cortés then adopted a slower and more brutal method. As each district was taken, its buildings were pulled down and the rubble used to fill the canals, so that horses and guns could operate and the defenders had no cover. Thousands of allied labourers carried out the demolition.

Inside the city conditions grew desperate. The defenders lacked fresh water and food, and Indigenous accounts later collected by Bernardino de Sahagún describe people eating lizards, grass and adobe, and dying of disease and hunger in large numbers.

The last stand at Tlatelolco

By late July the defenders had been pushed into Tlatelolco, the northern twin city of Tenochtitlan, home of the great market (see Tlatelolco’s Conquest by Tenochtitlan). Alvarado’s men reached its main temple and set it on fire. The remaining population was crowded into a small area near the lakeshore, under constant attack.

On 13 August 1521, the feast of Saint Hippolytus, Cuauhtémoc attempted to escape across the lake in a canoe. He was intercepted by a brigantine commanded by García Holguín and brought before Cortés. With his capture, organised resistance ended, and the surviving inhabitants were allowed to leave the ruined city.

Key people

• Hernán Cortés (1485–1547): Spanish commander who organised the siege and directed the brigantines.
• Cuauhtémoc (c. 1500–1525): the last Mexica ruler of Tenochtitlan, who led the defence.
• Pedro de Alvarado and Gonzalo de Sandoval: Cortés’s leading captains on the causeways.
• Ixtlilxóchitl of Texcoco: ruler of Texcoco and an important ally of the Spaniards.
• Martín López: the shipwright who built the 13 brigantines.
• The Tlaxcalans: Cortés’s most important allies throughout the war.

By the numbers

Consequences and legacy

The fall of Tenochtitlan broke the power of the Mexica and the Triple Alliance. Many former tributary states submitted to the Spaniards, while others were conquered in campaigns over the following years. For the Indigenous allies the victory at first seemed to promise freedom from Mexica rule, and Tlaxcala gained privileges from the Spanish crown, but all of central Mexico came under Spanish authority.

Cuauhtémoc remained a prisoner. Spaniards searching for the treasure lost on the Noche Triste tortured him by burning his feet. In 1525 Cortés took him on an expedition to Honduras and had him hanged, accused of plotting rebellion.

Cortés decided to build the capital of the new colony on the ruins. Mexico City rose on the site, its cathedral and palaces built partly with stone from the destroyed temples, and in 1535 it became the seat of the Viceroyalty of New Spain. Epidemics continued to devastate the Indigenous population in the decades that followed.

Myths and facts

• Myth: a few hundred Spaniards conquered the Aztec Empire alone. The siege was won by a coalition in which Indigenous allies far outnumbered the Spaniards. Many historians describe the war as partly a revolt of Mesoamerican peoples against Mexica dominance.
• Myth: the Mexica thought Cortés was the god Quetzalcoatl. The story that the Mexica believed Cortés was a returning god appears only in sources written decades later, and many historians now doubt it.
• Fact: disease mattered greatly. The smallpox epidemic of 1520 killed a large part of the population and the ruler Cuitláhuac before the siege began.

In Mexico the fall of Tenochtitlan is remembered as both an ending and a beginning. Cuauhtémoc is honoured as a national hero, with monuments such as the statue on Mexico City’s Paseo de la Reforma. At the Plaza of the Three Cultures in Tlatelolco, a plaque recalls 13 August 1521 not as a triumph or a defeat but as the painful birth of the mestizo nation.

Archaeology continues to uncover the old city beneath the modern one, above all at the Templo Mayor, the great temple excavated in the centre of Mexico City since 1978.

Timeline

• 1520, 30 June – 1 July: The Spaniards flee Tenochtitlan on the Noche Triste.
• 1520, late: Smallpox kills Cuitláhuac; Cuauhtémoc becomes ruler early in 1521.
• 1521, 28 April: The 13 brigantines are launched at Texcoco.
• 1521, late May: The besiegers take up positions on the causeways and cut the Chapultepec aqueduct.
• 1521, 30 June: A major Spanish assault fails; captured Spaniards are sacrificed.
• 1521, late July: The defenders are driven into Tlatelolco.
• 1521, 13 August: Cuauhtémoc is captured and resistance ends.
• 1525, February: Cuauhtémoc is executed during the Honduras expedition.

Why it matters

The fall of Tenochtitlan destroyed the most powerful state in Mesoamerica and opened three centuries of Spanish rule in Mexico. It set the pattern for later conquests in the Americas, combining a small European force, Indigenous alliances and the devastating effect of new diseases, and it is the founding event of modern Mexico City, a key moment in the wider Spanish conquest of the Aztec Empire.