The Aztec Empire that ruled over Central Mexico from 1429 to 1521 was a triple alliance between the Indigenous Nahua city-states of Tetzcoco, Tlacopan and Tenochtitlán. More than 500 small states comprised of an estimated 6 million people lived under the alliance’s rule. Montezuma was named huey tlahtoani, or king, of Tenochtitlán on September 15, 1502. “He was a warrior and well-respected military leader who maintained a vibrant city and culture, both politically and economically,” says Buddy Levy, author of Conquistador: Hernán Cortés, King Montezuma, and the Last Stand of the Aztecs. Montezuma’s empire grew in size, status and wealth despite three years of famine and three earthquakes—disasters that would topple a weaker leader.

Tenochtitlán was twice as large as Seville, the prosperous capital of southern Spain, but with a population as much as 10 times the size. Its dazzling location on an island in the center of Lake Texcoco—along with its towering pyramids and temples, vast plazas and canals that locals traversed by canoe—inspired wonder in the visiting Europeans, who had never seen a city of this scale. In a letter to Spain’s King Carlos V, Holy Roman Emperor, Cortés described bridges where “10 horses can go abreast,” and public squares with markets selling food and “jewels of gold and silver.” Montezuma’s palace complex included a zoo with aviary, art collections, armory, library, pleasure palace and botanic garden.

The Aztec ruler began studying the Spanish as soon as they landed. “The Spanish were constantly surrounded by spies who sent back information back to Montezuma. He wanted to learn more about their world, and it’s not hard to imagine that one day, the Spanish could be part of his,” says Matthew Restall, author of When Montezuma Met Cortés. “If we want to fault him, his sense of his own authority was such that he was not able to see how extensive the Spanish threat was.”

If it sounds too good to be true that the Spanish showed up to conquer a powerful empire and were perceived as gods fated to be its overlords, it’s because it is. “[The Aztecs] did not believe that their god Quetzalcóatl walked among them, nor were they impressed by a vision of [Christianity’s Virgin] Mary or one of the saints,” writes Rutgers University history professor Camilla Townsend in The Fifth Sun: A New History of the Aztecs.

Nor did Cortés—never shy about his exploits—ever mention in his writings that he was mistaken for Quetzalcóatl. The idea of a prophesied god returning was a Christian narrative overlaid on Aztec mythology surrounding Quetzalcoatl, says Restall, made popular in the 16th century by “Franciscans who came to convert the Nahuas to Christianity.” The Florentine Codex, written in 1555 by Nahuas educated in the Franciscan faith, emphasized this prophecy as a way to rationalize the conquest.

When Cortés sailed to Mexico from Cuba, looking for territory to conquer and riches to plunder in the name of the Spanish crown, he was an outlaw defying orders from Cuban Governor Diego Velasquez, who had canceled his exploratory expedition. “Cortés had gone completely rogue,” says Levy.

His letters to King Carlos V needed to justify his disobedience and claim he followed Spanish rules of conquest—which meant giving the Aztecs an opportunity to submit to the crown and Christ.

If Montezuma had immediately surrendered, it would have been something to write home about—but no one wrote home until almost a year later, when the Spanish conquered the city by force. “Throughout the entire 235 days, neither Cortés nor any other Spaniard in Tenochtitlán wrote a letter or report to the king, or to anyone outside the city, detailing their supposed control of city and empire,” Restall writes. “Yet they claimed to have ink and paper—to notarize Montezuma’s surrender.”

Firsthand accounts by locals show Montezuma’s life continuing normally after he takes in his Spanish guests, receiving ambassadors, envoys delivering tribute and giving public speeches. In his later letters to King Carlos, Cortés even reported that Montezuma went hunting and moved around the city with a retinue “of always at least 3,000 men.” Spanish priest and historian Bartolomé de Las Casas wrote to the king and high court officials to say Montezuma’s surrender was a lie. But his letter went unheeded, as accepting the surrender was critical to justifying the siege of Tenochtitlán.

Multiple outbreaks of European-borne disease decimated the Aztecs in the decades after 1519. The largest, lasting from 1545 to 1550, killing a reported 90 percent of the population in some areas. A second wave of the mysterious cocoliztli, the Nahua word for pestilence, came in 1576, bringing the estimated death toll to between 7 and 17 million people in the Mexican highlands. New research suggests that the cause may not have been smallpox, but salmonella.

Survivors were forced to adapt to life on new terms. Securing some degree of safety and possibly status required accepting Christianity and the “official” version of the meeting as part of the surrender—which is why, Restall argues, that version held sway for centuries. “The Aztec royal family continue[d] to have privileges after the conquest for generations,” he says. “They were elite, local rulers with property, wealth and power.” Montezuma’s daughter, Tecuichpochtzin, later known as Doña Isabel Moctezuma Tecuichpo, married conquistador Juan Cano. Her sons were considered Spanish nobles and their hereditary title, Duke of Moctezuma de Tultengo, is still in use.

After the conquest, few people were willing to go on the record about any wrongdoing—there were too many powerful people with something to gain, be it titles, lands, and other spoils of war. “It takes centuries to turn Tenochtitlán into Mexico City,” wrote Restall, “but only a few generations to spread a different kind of history, to tell a whole set of lies about Montezuma and the Aztecs and make them out to be historical truth.”