When Hernán Cortés's army made its final march on Tenochtitlan, the Aztec capital, the Spaniards were "maybe one half of one percent in raw numbers of that force," military historian Si Sheppard said on an episode of the Dwarkesh Podcast published October 1, 2026. Everyone else came from Mesoamerican peoples who, in Sheppard's words, saw the campaign as "their final reckoning with the Aztecs."
The episode's title asks how a few hundred Spanish soldiers toppled two empires. Its description puts the Aztec Empire at 6 million people and the Inca Empire at about 10 million, and it presents the conquests as an older precedent for today's talk of AI takeover. Sheppard's answer is that the question is partly misleading. Spanish steel and horses could win battles, he said, but the Spaniards could not have won the war "without the support of those indigenous allies."
His explanation rests on what the two empires were. On a map, he said, the Aztec Empire "seemed impressive. But this was an imperial construct." Both the Aztecs and the Inca ruled many peoples through a small elite. Sheppard noted that only a small number of their subjects spoke the imperial languages, Nahuatl and Quechua. When outsiders arrived with real military power, peoples who resented that rule saw a way out.
Tlaxcala's Hail Mary
The central case is Tlaxcala, a state that had never been absorbed by the Aztecs. When Cortés marched inland after landing on the coast, the Tlaxcalans first tried to expel him; Sheppard compared their reaction to an autoimmune system. He put the forces at a few hundred on Cortés's side against multiple thousands of Tlaxcalans. Cortés fought them to a standstill, and the two sides reached a new arrangement.
Sheppard said the switch made strategic sense for Tlaxcala. It was the last major power in Mesoamerica still able to go "toe-to-toe" with the Aztecs, and it was surrounded. It had been cut off from the coast and from sources of salt. The Aztecs were escalating the ritual "flower wars" they fought with Tlaxcala, and Sheppard said those battles were becoming more and more obviously wars of conquest. Allying with a small band of strangers was "a Hail Mary": a desperate chance to break out of a strategic trap.
Archaeologist David Carballo gives a similar picture in a 2021 essay on Tlaxcala's role. He describes Tlaxcallan as an independent political community that had resisted Aztec expansion for decades. It first met the newcomers with armed force, including Otomi warriors on its frontier, before an alliance formed. Carballo adds that the Tlaxcalans gave more than warriors. They supplied guides, food, refuge and knowledge of how their opponents fought.
The alliance was tested in 1520 after La Noche Triste, the "tragic night" when the Spaniards fled Tenochtitlan with heavy losses. Cortés escaped wounded with a minority of his troops. Sheppard said that if the Tlaxcalans had turned on him then, not one Spaniard would have survived. Instead they took the Spaniards back in. In Sheppard's account, they did this for their own reasons, "not out of any generosity or humanitarian impulse." They still saw the Spaniards as committed to the alliance.
They also set terms. Sheppard said the Tlaxcalans drove a hard bargain: they wanted territory carved out of the Aztecs' lands and their own fortress in Tenochtitlan once the war was over. "They saw this as them using the conquistadors, not the other way around," he said. He pointed to murals in the governor's mansion in Tlaxcala today. They show Tlaxcalan leaders and the conquistadors at the same scale, as diplomatic partners rather than as rulers and subordinates.
That Tlaxcalan view also has a later history. Carballo writes that Tlaxcalan leaders sought a privileged, partly autonomous position under the Spanish Crown. Later Tlaxcalan histories stressed partnership and faithful service to support those claims. Some Indigenous pictorial histories emphasize the first armed clashes, while later ones put diplomacy and loyalty to Spain in front. Researchers at the Getty, discussing the Florentine Codex, stress how Nahuatl, Spanish and pictorial narratives of the conquest diverge, and how Indigenous communities' perspectives differ from one another.
A coalition built from grievances
Tlaxcala was not alone. Sheppard said the Totonacs, whose lands Cortés reached first, had recently been brought under Aztec rule, resented it, and saw the outsiders as a chance to throw it off. The Chalco states on the shores of Lake Texcoco also "chafed under Aztec hegemony," he said. To them, too, the Spaniards offered a way to shake off Aztec demands and, in many cases, to get revenge.
The Spaniards also worked inside the Aztec system itself. The empire was formally the Triple Alliance, which Sheppard said was founded in 1428 as a coalition of three city-states: Tenochtitlan, Texcoco and Tlacopan. In 1516, a few years before Cortés arrived, the king of Texcoco died. Two of his sons fought a civil war over the succession, and Moctezuma II, the Aztec emperor, gave the title to one of them. When the Spaniards showed up, Sheppard said, the other brother sided with them immediately. To him, the newcomers were a path to the throne he felt he was owed, and perhaps a better overlord than the Aztecs. The memoir of the conquistador Bernal Díaz del Castillo describes rival claimants and factions at Texcoco. It says a ruler aligned with the Spaniards supplied labor and urged neighboring communities to join, which made Texcoco a base for the attack on Tenochtitlan.
Sheppard described this as a deliberate method. The Spaniards were "very, very clever," he said, at finding local sub-chiefs beneath the Aztec layer of authority who would listen to a simple pitch: why take orders from the Aztecs when the Spaniards offered a better deal. Sometimes they gave Spanish weapons to especially prized allies, local chiefs and warlords, to signal that they were special. Sheppard said this was effective in binding the coalition together.
In the conversation, the situation was compared to Russia and Ukraine after a century of trench warfare, with Russians sacrificing tens of thousands of Ukrainians. If a foreign force then offered Ukrainians help to march on Moscow, the comparison went, it would probably find takers. Sheppard agreed: "The old phrase is, the enemy of my enemy is my friend."
Spanish technology, local muscle
Sheppard's examples from the final campaign show Spanish know-how relying on local manpower. To take a city in the middle of a lake, Cortés needed to control the lake. One expedition climbed the volcano Popocatépetl, and men dangled on ropes inside the crater to scoop out sulfur for gunpowder. Another built brigantines, small sailing warships, in sections. Sheppard said "untold numbers of porters" carried the pieces over the mountains to be assembled and launched on the lake.
Díaz's memoir puts numbers on that effort. He reports 8,000 Indigenous carriers moving the materials from Tlaxcala, escorted by 8,000 warriors, with another 2,000 carrying provisions. The parts were assembled near Texcoco, and thousands more people worked each day to dig a canal for launching the boats.
Cusco: more allies at the end than at the start
Sheppard saw the same pattern in Peru. Francisco Pizarro's conquest of the Inca Empire began about a decade after Cortés's. After Pizarro seized Cusco, the Inca capital, and went to the coast to found what became Lima, he left his half-brothers in charge. In Sheppard's account, they provoked Manco Inca, whom Pizarro had installed as a puppet ruler, into open rebellion. Manco's forces besieged Cusco, a siege that lasted from 1536 into 1537. A handful of Spaniards were holed up in a couple of fortified buildings under attack day and night.
Sheppard said they would have been wiped out except for two things. Cusco's open plazas suited their cavalry. And local peoples kept coming over to their side. Among them were the mitmaq, communities the Inca had forcibly relocated, and the yanacona, whom Sheppard called serfs. He described them as the defeated and subordinated peoples the Inca had forced into the empire. Others came from much farther away: the Cañari from Ecuador and the Chachapoya from the Amazon basin. Even the Ayarmaca joined, a people who had once been rivals of the Inca for control of Cusco itself. Over many months, Sheppard said, the Spaniards ended the siege with more allies than they began with. "Without that, they would have been wiped out at Cusco."
Historian María Concepción Bravo Guerreira's 2003 study of Cañari and Chachapoya alliances supports this. Drawing on sixteenth-century chronicles and Indigenous petitions, it ties those alliances to earlier Inca conquest, forced relocation and reprisals during the Inca civil war. It records that relocated communities in Cusco helped the Spaniards. Mark Cartwright's history of the siege adds that Indigenous allies brought supplies into the city at night. The alliances did not end with the siege. Bravo Guerreira finds descendants of these groups serving as guards and messengers in colonial times, exempt from tribute, and Chachapoya auxiliaries fighting on the royal side in later wars among Spaniards.
Why the defenders could not do the same
The Spaniards were divided too. Diego Velázquez, the governor of Cuba, was furious that Cortés had gone beyond his orders. He sent Pánfilo de Narváez with a force that Sheppard said was larger than the one Cortés had first brought. Cortés left his lieutenant Pedro de Alvarado in Tenochtitlan, marched to the coast, beat Narváez in a minor battle and won over most of his men. Sheppard said Cortés's pitch was, in effect: why are we fighting, when the empire is at my disposal and we can share the riches? The question put to Sheppard also noted that in Peru, Pizarro's second-in-command Diego de Almagro, angry over the spoils, besieged and captured Cusco.
Sheppard was asked why the Spaniards could exploit native divisions while Moctezuma and Manco Inca could not exploit Spanish ones. His answer was that the two kinds of division were different. The conquistadors were nearly all Castilians with shared backgrounds, and their quarrels were personal rivalries within one system. Faced with a real common threat, he said, they would have united. The divisions among Indigenous peoples, by contrast, were "differences between entire societies."
There was an attempt. Sheppard said Cuitláhuac, who succeeded Moctezuma after the Spaniards were driven out of Tenochtitlan, sent envoys to the Tlaxcalans and to the Tarascans, another power that had stayed independent of the Aztecs, proposing a new alliance of native peoples against the outsiders. The younger generation of Tlaxcalans thought about it. But the old men who still held power had fought the Aztecs for decades and saw them as the real existential threat, so they rejected it. The Tarascans, Sheppard said, wanted nothing to do with the Aztecs. In his paraphrase of their attitude: this is your problem, and if you get taken out, it is no loss to us.
Cortés's own letter to Charles V, dated October 30, 1520, reports that communities near Veracruz shifted toward Narváez because his expedition looked stronger. Indigenous communities could, in that account, choose between rival Spaniards. But the rivalry ended quickly when Cortés captured Narváez.
The only way to turn the tables, Sheppard argued, would have been to play rival European powers against each other. That did happen to some degree later. But in these early decades, he said, the Spanish were "the only game in town." If the English, French, Dutch or even the Ottomans had been players in colonizing the Americas at that stage, local peoples might have recognized different cultures and used them against each other.
What the allies did not foresee
Sheppard said many Indigenous elites thought they were using the Spaniards to their advantage. What they could not imagine was how many Spaniards, and later other Europeans, would follow. Their closed worlds, he said, did not let them think that people from such distances could arrive in such numbers. In the long run that demographic tide worked against them. As in Australia and New Zealand, Sheppard said, they became a minority in their own country. Carballo makes a related point about Tlaxcala's allies: the Aztec Empire had mostly ruled through indirect tribute, while the Spanish colonial government that followed brought much more intrusive political, religious and economic control.