Norse and Aztecs · CHAPTER 11 ·
Fall of the Aztec Empire
Chapter 11 of Climate and Innovation: The Norse and the Aztecs, c. 790–1521: “The Flower Wars and the End of the System”
For decades the Triple Alliance fought ritualised flower wars against Tlaxcala, Huexotzinco and Cholula and blockaded Tlaxcala, making enemies it never conquered. In September 1519 Tlaxcala chose alliance with a few hundred Spaniards, and with an epidemic they turned Tenochtitlan’s lake against it; the city fell in 1521.
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The map above is the world of The Aztec Empire, May–August 1521 — The siege of Tenochtitlan.
Part of IB History: The Norse and the Aztecs →
SHORT EXPLANATION
The Triple Alliance of Tenochtitlan, Texcoco and Tlacopan brought tribute to the island capital, but its power also gave other peoples reasons to oppose it. For decades it fought flower wars, or xochiyaoyotl, against Tlaxcala, Huexotzinco and Cholula: agreed battles for sacrificial captives that left those states independent. Tlaxcala lived under a long blockade, and the Tarascan kingdom in the west had crushed a Mexica army around 1478–79. On the 1521 map, blue states independent of or opposed to the Alliance surround its red core around the lake.
Hernán Cortés arrived on the Gulf coast in April 1519 with about 500 soldiers. The tribute-paying Totonacs of Cempoala and then independent Tlaxcala joined him, turning local grievances into a coalition. Smallpox arrived with another Spanish expedition in 1520 and killed vast numbers in central Mexico, including Cuitlahuac, Tenochtitlan's ruler. In 1521 a largely Indigenous army besieged the city: Spanish brigantines broke through the dike, allies cut the Chapultepec aqueduct and the causeways became battle lines. Tenochtitlan fell on 13 August, after tens of thousands, perhaps far more, had died. Historians increasingly describe its fall as a war of Mexican peoples against Mexica rule, with Spaniards playing a decisive part.
The full story
Why did the Triple Alliance leave Tlaxcala and its neighbors outside its empire while fighting them repeatedly? The answer depends on whom we believe. Fernando de Alva Ixtlilxochitl says that in 1454, the last year of the great famine, rulers agreed to fight Tlaxcala, Huexotzinco and Cholula on fields usually near Atlixco. The combatants would take captives for sacrifice without taking each other's lands. Diego Durán credits the adviser Tlacaelel with the idea. Ross Hassig sees repeated fighting as a relatively cheap way to wear down strong enemies; Barry Isaac treats the ritual story as a later explanation for failure to conquer them. Meanwhile, tributary provinces encircled Tlaxcala. Tlaxcalans told the Spaniards that the blockade had deprived them of salt and cotton. Whatever the wars' purpose, their result was an independent neighbor with a long grievance.
Sacrifice also connected religious obligations to imperial politics. Mexica religion taught that the gods had sacrificed themselves to create the sun and needed human blood to keep the world moving. Many victims were war captives or tribute from subject peoples. The scale remains disputed: for the Templo Mayor's rededication in 1487, Durán gave 80,400 victims, while an Indigenous pictorial source gives 20,000; many historians consider the larger figures inflated. Since 2015 excavations of the great skull rack have identified 655 skulls, including women and children. When Cortés reached Cempoala in 1519, its Totonac ruler complained about Mexica tribute collectors. Tlaxcala fought the Spaniards and then allied with them in September. Existing enemies of the Alliance now had a way to act together.
The coalition's advance brought further violence. At Cholula in October 1519 Spaniards and their allies killed thousands, Cortés acknowledging about 3,000. They entered Tenochtitlan on 8 November. In May 1520 Pedro de Alvarado's men massacred celebrants at the festival of Toxcatl. The Spaniards fled along the Tlacopan causeway on the night of 30 June, suffering heavy losses; after the battle of Otumba they found refuge in Tlaxcala. From about October, smallpox brought by Pánfilo de Narváez's expedition swept Tenochtitlan for sixty days.
Cortés returned with fewer than a thousand Spaniards, tens of thousands of Indigenous allies and thirteen brigantines, small sailing warships built with Tlaxcalan help. From late May 1521 the attackers cut the aqueduct, contested canoe traffic and advanced along the causeways. These were the connections that had supplied a city of 200,000. Control of them allowed the besiegers to turn the lake's defenses against its inhabitants: hunger, thirst and disease accompanied the fighting until the city fell on 13 August.
FULL EXPLANATION
What were the flower wars for?
A battle fought by agreement can serve more than one purpose, and the evidence for the flower wars has led historians to different conclusions. Durán and Alva Ixtlilxochitl describe rulers arranging combat to obtain captives for the gods and train young warriors. Andrés de Tapia reported Moctezuma II saying that the Mexica kept Tlaxcala independent for this purpose. Ross Hassig proposed another advantage in 1988: an empire could commit only part of its forces to repeated campaigns and gradually exhaust a strong neighbor. He cited Chalco, which resisted for decades before its conquest around 1465. Barry Isaac argued in 1983 that the ritual story reversed the explanation: the Mexica had failed to conquer Tlaxcala, and later writers made the failure look intentional. Frederic Hicks regarded the wars as wars of conquest. The evidence fits a struggle that began as conquest and was later explained as ritual, although its purposes and the timing of any change remain disputed.
Sacrifice: numbers, sources and caution
The competing numbers for Mexica sacrifice cannot be separated from the people who recorded them. Spanish writers could use sacrifice to justify conquest and conversion; Mexica chroniclers could enlarge a ceremony to magnify their rulers' power. For the Templo Mayor's rededication in 1487, Durán, Alvarado Tezozómoc and several annals give 80,400 victims. Chimalpahin and Torquemada give other large figures; the Codex Telleriano-Remensis records 20,000 in Indigenous number signs. Michel Graulich concluded in 1991 that 20,000 was a minimum and 80,400 possible. Others argue that the higher figure would have been logistically implausible. Archaeology lets us count remains without relying on a chronicler's motives, but those remains cannot establish the total for one ceremony. By 2023 the Huei Tzompantli had yielded 655 skulls: about 60 percent male, 38 percent female and 2 percent children. Sacrifice was real, large and politically charged. Its precise scale remains uncertain.
Whose conquest? Indigenous allies and the new history
For centuries a few hundred Spaniards occupied the center of the story of Tenochtitlan's fall. The Indigenous participants become harder to treat as supporting figures once we ask what the Spaniards needed and what their allies wanted. Matthew Restall emphasizes their dependence on Indigenous allies, guides, porters and interpreters, including the Nahua woman Malintzin. Reading Nahuatl annals, Camilla Townsend shows Tlaxcalans, Texcocans, Chalcans and others pursuing their own interests. Laura Matthew and Michel Oudijk's 2007 collection calls the allies Indian conquistadors. The painted Lienzo de Tlaxcala presents the campaign as a Tlaxcalan victory while making a claim for privileges from the Spanish crown. Smallpox killed a large share of central Mexico's people and many rulers before the siege; Spanish weapons and ships mattered too. The conquest can thus be understood as a revolt of subjects and rivals against Mexica power, made decisive by Spanish intervention and disease. It leaves a question for this atlas: how had a system so successful against its environment produced so many people willing to destroy it?
Key places on the map
On this day
Why it happened
Tribute and encirclement created enemies. The tribute that fed Tenochtitlan came from conquered communities that retained their own rulers. Totonac lords complained about its collectors. Tlaxcala remained independent, but tributary provinces surrounded it and, according to complaints recorded by Spaniards, cut it off from salt and cotton. The arrival of an outside force gave subjects and rivals an opportunity to change their position. Many joined the Spaniards within months.
Unfinished wars left strong rivals. Tlaxcala, Huexotzinco and the Tarascan kingdom had remained beyond Alliance control. Around 1478–79 a Tarascan army destroyed a Mexica force near Taximaroa; Durán's figure of more than 20,000 dead is probably inflated. Fortifications marked the frontier, including Mexica Oztuma and Tarascan strongholds. These undefeated states were potential allies for an invader. Tlaxcala proved especially consequential in 1520, when it sheltered Cortés's broken army and gave it a base for its return.
A new disease met a population without immunity. Smallpox reached central Mexico with Narváez's expedition in 1520. The disease had not previously reached the Americas, and people without immunity faced its rapid spread. Nahua accounts in the Florentine Codex describe victims so covered with sores that they could not move and others starving because no one could care for them. Cuitlahuac died after about eighty days as ruler. The epidemic weakened the city's defenders before the siege, while sparing the Spaniards, most of whom had survived childhood exposure.
The engineered lake had points of failure. An island city needed connections: causeways to land, an aqueduct for drinking water and canoes to carry food. A besieger could attack each one. The attackers severed the Chapultepec aqueduct at the start of the siege, while Spanish brigantines built on the lakeshore broke through the dike that had freshened the lagoon. Indigenous allies provided troops and knowledge of the targets. The works that made the city viable also gave its enemies places to interrupt its supply.
THE TURNING POINT
Tlaxcala chooses alliance, September 1519. Tlaxcala's rulers chose alliance with Cortés in September 1519 after fighting his small force and negotiating with him. Their decision belonged to an independent state's long conflict with the Triple Alliance. It gave the Spaniards soldiers and support, and, after the retreat from Tenochtitlan in 1520, a refuge from which to return. Without Tlaxcala, Cortés would have lacked that secure base and the army of tens of thousands that came back to the lake. Mesoamerican political choices were central to the conquest.
What it changed
The fall of Tenochtitlan. Tenochtitlan fell on 13 August 1521, when Cuauhtemoc, its last ruler, was captured on the lake. Hunger, thirst, disease and violence had killed tens of thousands; chroniclers' totals of up to 240,000 cannot be checked. A plaque erected at Tlatelolco in the 1960s reads, in translation, “It was neither triumph nor defeat; it was the painful birth of the mestizo people that is the Mexico of today.”
A population catastrophe. Smallpox in 1520 was only the beginning of a succession of epidemics. Cocoliztli struck in 1545 during a severe drought recorded in tree rings. Within a century central Mexico's population may have fallen by 80–90 percent, from an uncertain 5–25 million to about 1 million. Along with the devastation of families and communities came the loss of much of the labor that maintained the lake's dikes, canals and fields.
Spain inherits the lake. The Spaniards rebuilt on Tenochtitlan's ruins, but the basin's water problems remained. Much of the Mexica knowledge and labor used to manage them was lost within a generation. Floods in the following century led the newcomers to begin draining the lake. The epilogue follows that choice from the great flood of 1629 to the sinking of Mexico City today.
DISCUSSION QUESTION — Why did the Mexica system, so effective against the environment, prove so vulnerable to its human enemies?
The island concentrated perhaps 200,000 people where canoes and causeways could supply them. Those same connections could be blocked: the besiegers cut the aqueduct, fought along the causeways and used brigantines to contest the lake. The empire that fed the city through tribute had also made enemies among subjects and surrounded rivals. Their tens of thousands of troops gave the Spaniards a coalition capable of conducting the siege. Smallpox, a shock no Mesoamerican society could have anticipated, killed leaders and defenders beforehand. Historians differ in the weight they give Indigenous politics, disease and Spanish technology. Together these forces exposed a vulnerability in a system built to manage water, frost and food.
An interesting fact
In the 1550s Tlaxcala's town council commissioned a great painted cloth, the Lienzo de Tlaxcala, that showed its warriors beside the Spaniards from their first alliance through the siege and later campaigns. The pictures had a practical purpose: the council sought recognition of Tlaxcala's loyalty and exemptions from tribute from the Spanish crown. The original is lost, but later copies, including one made in 1773, preserve an account in which Tlaxcalans are the heroes.
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