How the mighty Tenochtitlan, capital city of the Aztecs, fell to Spanish conquistadors

The Mexica founded Tenochtitlan around 1325, after years of wandering in search of a promised land.

According to legend, priests saw a sign from their god Huitzilopochtli, an eagle perched on a cactus with a serpent in its beak, and chose the island site for their new home.

As they built their city on the lake, they gradually forged alliances with other city-states, including Texcoco and Tlacopan, which formed the Triple Alliance. 

By the reign of Moctezuma I, who ruled from 1440 to 1469, Tenochtitlan had evolved into the dominant force in the region.

His reign expanded on earlier military victories achieved under Itzcoatl, who had established the Triple Alliance and led the initial defeat of the Tepanecs.

The Aztecs imposed tribute on defeated peoples and forced many into military service or sacrificial rituals.

Wealth flowed into the capital, and tribute goods such as cacao, cotton, obsidian, and feathers lined the streets and storehouses.

The city’s population expanded alongside its political reach, because chinampa farming and water channels supported its growth.

Estimates suggest the city held between 200,000 and 300,000 people, making it one of the largest urban centres in the world at the time.

Its streets, canals, and causeways followed a grid-like pattern, and public buildings rose above residential zones and markets that supplied food and trade goods to every district. 

Massive temple-pyramids, such as the Templo Mayor, towered over the city centre, where priests performed sacrifices to honour the gods and ensure the world’s continued survival.

Through both fear and belief, the state enforced loyalty. By the early 1500s, under the rule of Moctezuma II, the empire controlled more than five million people. 

Cortés arrived on the Gulf Coast in early 1519, where he landed near present-day Veracruz.

After he was officially sent to explore, he quickly defied orders from Cuba’s governor and got ready to move inland.

His forces included around 600 men, a handful of horses, and several cannons, but, along the way, they encountered Indigenous peoples who were either hostile or eager to ally with them against the Aztecs. 

A key figure in Cortés’ success was Malintzin, also called Doña Marina by the Spanish.

She was translator, advisor, and cultural mediator, who enabled Cortés to communicate with local leaders and learn about political tensions.

Through her assistance, he gained allies among the Totonacs and later the Tlaxcalans, who provided warriors and intelligence.

The Tlaxcalans, who had long resisted Aztec domination, viewed the Spanish as an opportunity to overturn the regional balance of power.

As the Spanish marched toward the Valley of Mexico, they strengthened their numbers and prepared to confront the empire’s core. 

Moctezuma II received reports of the newcomers’ weapons, animals, and tactics.

Unsure how to respond, he chose to allow the Spanish to enter the capital in November 1519, where he greeted Cortés with gifts and offered hospitality, hoping to control the situation through diplomacy and ceremony.

The Spanish accepted the welcome but quickly used it to their advantage, positioning themselves to take over the city from within. 

After entering Tenochtitlan, Cortés moved to seize control of its leadership. He placed Moctezuma under house arrest and forced him to act as a puppet in order to command obedience from the population.

Then, the Spanish demanded gold and began interfering in religious practice.

Discontent spread throughout the city, though the people remained cautious. 

Cortés left the city in 1520 to confront a rival Spanish expedition sent to arrest him for disobedience.

He defeated the force and recruited additional troops, but during his absence, tensions erupted in Tenochtitlan.

His lieutenant, Pedro de Alvarado, Cortés’ second-in-command, ordered the massacre of hundreds of unarmed nobles during a festival, fearing they planned an uprising.

The killings sparked a revolt that engulfed the city. 

When Cortés returned, he found the population in open rebellion. Aztec warriors surrounded the palace where the Spanish had taken shelter, and Moctezuma, now hated by his own people, attempted to negotiate.

During one such attempt, he suffered injuries from stones thrown by the crowd and later died.

His exact cause of death remains unclear, though Aztec and Spanish sources give conflicting accounts. 

When the Spanish found themselves trapped in the city, they planned an escape.

On the night of 30 June 1520, they attempted to flee across the causeways under cover of darkness.

That failed escape became known as La Noche Triste, the Night of Sorrows, because Aztec warriors attacked with canoes and weapons from both land and lake.

Many Spanish soldiers drowned under the weight of gold they tried to carry, and hundreds of their Indigenous allies died beside them. 

The survivors limped away from the city and retreated to Tlaxcala. There, Cortés regrouped his forces, requested reinforcements, and began plotting revenge.

Meanwhile, disease had already begun to devastate the Aztec population. The smallpox epidemic began with an infected African slave, possibly named Francisco de Eguía, who had arrived with the Narváez expedition.

Smallpox spread rapidly and killed thousands. Some regions lost over half their population in only a few months.

Among the victims was Cuitláhuac, Moctezuma’s successor, who had taken command during the uprising. 

The Spanish returned months later with a rebuilt army. They carried newly constructed brigantines, which they assembled at the lake’s edge to control the waters around the city.

They destroyed towns by using their Indigenous alliances, blocked supply routes, and began a siege that would destroy Tenochtitlan from the outside in. 

Cortés launched the siege in May 1521, dividing his forces into three groups that advanced along the main causeways.

The brigantines patrolled the lake and cut off the city’s access to food and water.

Aztec warriors resisted fiercely, defending barricades and counterattacking with canoes, but the pressure increased with each passing day. 

Cortés employed a harsh campaign of destruction, and his forces demolished neighbourhoods and killed civilians to weaken morale.

Though some sources claim wells were poisoned, there is no clear evidence that this was a deliberate tactic.

The Spanish also used captured prisoners to send messages demanding surrender.

Yet Cuauhtémoc, the new emperor, refused to yield. Cuauhtémoc was a young but determined leader around 25 years old and had earned respect for his courage and military skill.

He continued to lead resistance from within the shrinking city. 

Unfortunately, famine struck hard, with survivors later described people eating weeds, leather, and even human flesh to stay alive.

The canals, once used for transport and farming, filled with bodies. The smell of death lingered across the island.

Those who attempted escape were killed or captured by the Spanish and their allies. 

Spanish artillery and brigantine fire pounded what remained of the city’s defences.

As the population dwindled, Cuauhtémoc tried to organise a final defence, hoping that the gods would intervene or that the Spanish might falter.

His warriors continued to fight, but they no longer had the strength or numbers to prevent defeat. 

Cuauhtémoc attempted to flee the city in a canoe in August 1521, but Spanish forces captured him on the lake.

He was brought before Cortés and asked to order a surrender. On 13 August, after nearly three months of siege, the city fell.

The Spanish entered the ruined capital, where they looted the remains and executed some of the surviving defenders.

Others were taken prisoner or enslaved. Bernal Díaz del Castillo, one of Cortés’ soldiers, later wrote that the destruction was so complete that “we could not walk without treading on the bodies and blood of the dead.” 

The destruction of Tenochtitlan was the moment of the fall of the Aztec Empire.

Temples had been toppled, homes destroyed, and streets choked with corpses.

Historians estimate that over 100,000 Aztecs died during the siege, with tens of thousands more perishing in the aftermath.

The city that had once rivalled the largest in Europe lay buried beneath rubble and ash. 

In the months that followed, the Spanish founded Mexico City on the ruins. They enslaved many survivors, imposed Christianity, and built churches where temples had once stood.

A new colonial order replaced the old, enforced by violence and justified by religion.

Indigenous traditions survived in hidden corners, but Spanish rule changed every system of life.

Even in defeat, Aztec language, cuisine, and customs endured in Mexican identity, long after the empire’s fall. 

Ultimately, Tenochtitlan fell because of a perfect storm of war, betrayal, disease, and starvation.

Though the empire collapsed, memories of its splendour persisted in Indigenous memory and Spanish records.