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 →
BRIEF EXPLANATION — THE ESSENTIAL ARGUMENT
The Mexica system fell in 1521 because the empire of the Triple Alliance, the partnership of Tenochtitlan, Texcoco and Tlacopan that fed Tenochtitlan with tribute, had also made enemies, and those enemies, joined by a few hundred Spaniards and an epidemic, turned the city’s lake against it. For decades the Triple Alliance had fought ritualised battles called flower wars, xochiyaoyotl in Nahuatl, fought on agreed fields somewhat like a scheduled tournament with lethal stakes, against the independent city-states of Tlaxcala, Huexotzinco and Cholula, taking captives for sacrifice without conquering them. Tlaxcala, ringed by provinces that paid tribute to the Mexica, lived under a long blockade, and in the west the Tarascan kingdom had crushed a Mexica army around 1478–79. On the map of 1521, blue marks the states independent of or opposed to the Alliance, and it now surrounds the red core around the lake. An empire that had defeated frost and flood was undone by the peoples it ruled and the neighbours it had failed to conquer.
The invasion of 1519 gave those enemies their chance. When Hernán Cortés landed on the Gulf coast in April 1519 with about 500 soldiers, the Totonacs of Cempoala, who paid tribute to the Mexica, and then independent Tlaxcala chose to ally with him. Smallpox, arriving with a second Spanish expedition in 1520, killed vast numbers in central Mexico, including the new ruler Cuitlahuac. In 1521 Spanish brigantines, small sailing warships used on the lake much like modern patrol boats, broke the dike, allies cut the Chapultepec aqueduct and the causeways became battle lines, so the engineered lake became a trap for a starving city that fell on 13 August. Tens of thousands of people, perhaps far more, died in the siege. Most of the besieging army was Indigenous, and historians now describe the fall of Tenochtitlan as a war of Mexican peoples against Mexica rule in which Spaniards played a decisive part.
The full story
The flower wars, ritualised battles fought by agreement to take captives, somewhat like scheduled tournaments with lethal stakes, show how the empire managed enemies it could not, or chose not to, conquer. According to the Texcocan chronicler Fernando de Alva Ixtlilxochitl, the Alliance agreed in 1454, in the last year of the great famine, to fight Tlaxcala, Huexotzinco and Cholula on agreed fields, usually near Atlixco, to take captives for sacrifice while leaving each other’s lands untouched. Diego Durán credits the Mexica adviser Tlacaelel with the idea. Ross Hassig argues that these were deliberate wars of attrition, cheap ways to wear down strong enemies, while Barry Isaac argues that the ritual explanation was invented later to hide a failure to conquer. Meanwhile the Alliance encircled Tlaxcala with tributary provinces, conquered regions that paid regular tribute like a tax, and, according to Tlaxcalan complaints recorded by the Spaniards, cut off its salt and cotton. Exclusion created a neighbour with every reason to seek revenge.
Human sacrifice was central to Mexica religion, which taught that the gods had sacrificed themselves to create the sun and needed human blood to keep the world in motion, and its scale is debated. Chroniclers claimed tens of thousands of victims at the rededication of the Templo Mayor in 1487, with Durán giving 80,400, while an Indigenous pictorial source gives 20,000 and many historians think the larger figures inflated. Excavations of the great skull rack since 2015 have identified 655 skulls, including women and children. Sacrifice mattered politically because many victims were war captives or tribute from subject peoples, which deepened the resentment the empire inspired. When Cortés reached Cempoala in 1519, the Totonac ruler complained of Mexica tribute collectors, and in September Tlaxcala, after fighting the Spaniards, chose to ally with them. The resentment that tribute and sacrifice had built became the raw material of the coalition that destroyed the city.
The conquest combined Indigenous alliances, epidemic disease and the lake itself. At Cholula in October 1519 the Spaniards and their allies killed thousands, Cortés admitting about 3,000, and on 8 November they entered Tenochtitlan. In May 1520 Pedro de Alvarado’s men massacred celebrants at the festival of Toxcatl, and on the night of 30 June the Spaniards fled along the Tlacopan causeway with heavy losses, reaching Tlaxcala after the battle of Otumba. Smallpox, which arrived with Pánfilo de Narváez’s expedition, raged through the city from about October 1520 for sixty days. Cortés returned with thirteen brigantines, small sailing warships built with Tlaxcalan help and used on the lake much like modern patrol boats, tens of thousands of Indigenous allies and under a thousand Spaniards. From late May 1521 the aqueduct was cut and the city blockaded until it fell on 13 August, its people dying of hunger, thirst and disease. The siege worked because the aqueduct, causeways and canoe routes that had fed a city of 200,000 were the very points a besieger could cut.
DEEP EXPLANATION — EVIDENCE & INTERPRETATION
What were the flower wars for?
The purpose of the flower wars is one of the classic debates of Aztec history, and each interpretation rests on different sources. The chronicles of Durán and Alva Ixtlilxochitl present them as ritual combat agreed among rulers to supply captives for the gods and training for young warriors, and the conquistador Andrés de Tapia reported Moctezuma II saying that the Mexica kept Tlaxcala unconquered for that reason. Ross Hassig argued in 1988 that the wars were a strategy of attrition, letting a large empire commit a small share of its forces while slowly wearing down powerful neighbours, and he points to Chalco, which was fought for decades before being conquered around 1465. Barry Isaac argued in 1983 that the flowery war idea was a later rationalisation, a face-saving story covering a real inability to conquer Tlaxcala and its allies. Frederic Hicks argued that they were simply wars of conquest. The evidence fits a war that began as conquest and was later explained as ritual.
Sacrifice: numbers, sources and caution
Few subjects require more care in evidence than the scale of Mexica sacrifice, because the sources were written by people with strong reasons to exaggerate or minimise. Spanish writers used sacrifice to justify conquest and conversion, while some Mexica chroniclers magnified their rulers’ power through the size of their ceremonies. For the rededication of the Templo Mayor in 1487, Durán, Alvarado Tezozómoc and several annals give 80,400 victims, Chimalpahin and Torquemada give other large figures, and the Codex Telleriano-Remensis, using Indigenous number signs, gives 20,000. Michel Graulich concluded in 1991 that 20,000 was a minimum and 80,400 possible, while others argue that the logistics make the higher figure implausible. Archaeology offers firmer but partial evidence, because skulls and offerings can be counted and carry no author’s motive. The Huei Tzompantli had yielded 655 skulls by 2023, about 60 percent male, 38 percent female and 2 percent children. Sacrifice was real, large and politically charged, and its precise scale remains uncertain. A responsible account names the range, the sources and their motives, and does not let the numbers stand in for an explanation.
Whose conquest? Indigenous allies and the new history
For centuries the fall of Tenochtitlan was told as the triumph of a few hundred Spaniards, and recent scholarship has transformed that story by taking Indigenous sources and allies seriously. Matthew Restall argues that the Spaniards depended at every stage on Indigenous allies, guides, interpreters and porters, including the Nahua woman Malintzin, who interpreted for Cortés. Camilla Townsend, reading Nahuatl annals, shows Tlaxcalans, Texcocans, Chalcans and others pursuing their own interests, and the essays edited by Laura Matthew and Michel Oudijk in 2007 call the allies Indian conquistadors. Tlaxcalan memory, preserved in the painted Lienzo de Tlaxcala, presents the war as their victory. Smallpox, which killed a large share of central Mexico’s people and many rulers, also weakened the city before the siege. In this reading the end of the Mexica system was a revolt of the empire’s subjects and rivals, made decisive by Spanish weapons, ships and disease. The question for this atlas is how a system so successful against its environment had 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 empire that fed Tenochtitlan rested on tribute from conquered peoples who kept their own rulers and resented the burden, and on the encirclement of independent rivals. Tlaxcala, surrounded by Mexica tributary provinces and reportedly cut off from salt and cotton, nursed long grievances, and Totonac lords complained of tribute collectors. When an outside force appeared, these peoples saw a chance to overturn Mexica rule, and many took it within months.
Unfinished wars left strong rivals. The Alliance never conquered Tlaxcala, Huexotzinco or the Tarascan kingdom, whose army destroyed a Mexica force near Taximaroa around 1478–79, killing, by Durán’s probably inflated count, over 20,000 men. Fortified frontiers faced each other, with the Mexica fortress of Oztuma against Tarascan strongholds. These undefeated neighbours gave any invader potential allies and a secure base, which Tlaxcala provided for Cortés in 1520 when he retreated from the city with his army broken.
A new disease met a population without immunity. Smallpox had never reached the Americas, so nobody had immunity, and it spread rapidly after arriving with Narváez’s expedition in 1520. The Nahua accounts in the Florentine Codex describe victims too covered with sores to move and many who starved because nobody could care for them. The epidemic killed the ruler Cuitlahuac after about eighty days in power and weakened the defenders before the siege, while sparing the Spaniards, most of whom had survived childhood exposure.
The engineered lake had points of failure. Tenochtitlan depended on causeways for land access, an aqueduct for drinking water and canoes for food, all of which could be cut. The dike that had freshened the lagoon became an obstacle that Spanish brigantines, small sailing warships built on the lakeshore, broke through, and the aqueduct from Chapultepec was severed at the start of the siege. The very works that had made the city great gave a besieger clear targets, and the Spaniards’ allies knew exactly where they were.
THE TURNING POINT
Tlaxcala chooses alliance, September 1519. The decision of Tlaxcala’s rulers to ally with Cortés in September 1519, after defeating and then negotiating with his small force, is the hinge of this chapter. Without Tlaxcala the Spaniards would have had no secure base, no army of tens of thousands and no refuge after their flight from Tenochtitlan in 1520. The choice was made by an independent state pursuing its own long war against the Triple Alliance. It shows that the fall of the Mexica system came from within Mesoamerica’s own politics as much as from outside.
What it changed
The fall of Tenochtitlan. The city fell on 13 August 1521 when Cuauhtemoc, the last ruler, was captured on the lake. Tens of thousands of people had died of hunger, thirst, disease and violence, and the chroniclers’ figures of up to 240,000 cannot be checked. A plaque set up 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 followed by further epidemics, including the cocoliztli of 1545, which struck during a severe drought recorded in tree rings. Central Mexico’s population fell by perhaps 80–90 percent within a century, from an uncertain starting point of perhaps 5–25 million to about 1 million. The labour that had maintained the lake system, its dikes, canals and fields, largely disappeared.
Spain inherits the lake. The Spaniards rebuilt the city on the ruins and inherited its hydraulic problems without the Mexica knowledge or labour that had managed them. Floods in the following century led them to begin draining the lake, a choice whose consequences, from the great flood of 1629 to the sinking of Mexico City today, the epilogue examines. The skills and labour that had kept the lake in balance were lost within a generation.
DISCUSSION QUESTION — Why did the Mexica system, so effective against the environment, prove so vulnerable to its human enemies?
The Mexica system was built to manage water, frost and food, and the same features that made it effective against nature made it exposed to a coordinated human attack. Concentrating perhaps 200,000 people on an island made the city efficient to feed by canoe and causeway, but it also meant that cutting the aqueduct, controlling the lake with brigantines and blocking the causeways could starve it. The tribute empire that supplied food also produced resentment among subject and encircled peoples, who provided the tens of thousands of allies without whom the Spaniards could not have won. Smallpox, a shock no Mesoamerican society could have anticipated, removed leaders and defenders at the decisive moment. Historians differ on the weight of each factor, with Restall and Townsend stressing Indigenous politics and others stressing disease and Spanish technology. The transferable insight is that systems optimised for one kind of threat can concentrate vulnerability to another.
An interesting fact
The most detailed Indigenous picture of the conquest was painted to win privileges from the Spanish crown. Around the 1550s the town council of Tlaxcala commissioned the Lienzo de Tlaxcala, a great painted cloth showing scene after scene of Tlaxcalan warriors fighting beside the Spaniards, from the first alliance to the siege of Tenochtitlan and later campaigns. Its purpose was to prove Tlaxcala’s loyalty and earn exemptions from tribute. The original cloth has been lost, and historians study it through later copies, including one made in 1773, as a Tlaxcalan account in which the Tlaxcalans are the heroes.
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