<P> Although some popular sources put the number as high as 350,000, the most common estimates of the population are of over 200,000 people . One of the few comprehensive academic surveys of Mesoamerican city and town sizes arrived at a population of 212,500 living on 13.5 km (5.2 sq mi), It is also said that at one time, Moctezuma had rule over an empire of almost five million people in central and southern Mexico because he had extended his rule to surrounding territories to gain tribute and prisoners to sacrifice to the gods . </P> <P> When Cortés and his men arrived in Tenochtitlan, Moctezuma II, who precariously ruled over a large empire, chose to welcome Cortés as an honored guest, rather than risk a war which might quickly be joined by aggrieved indigenous people . Moctezuma may have feared that Cortés was the returning god Quetzalcoatl, because the Spanish arrival coincided with the close of an Aztec calendar cycle consistent with such a return . This claim is found in the Florenino Codex, among other early sources, and accepted as true in many later histories . However, some scholars doubt it . </P> <P> As Cortés approached the great city of Tenochtitlan, the natives put on many events . One particular event was the most important of them all, the celebration of Toxcatl . This event was when the most prominent warriors of altepetl would dance in front of a huge statue of Huitzilopochtli . The Spanish leader, Pedro de Alvarado, who was left in charge, worried that this would be the day that the natives would plan a surprise attack on them . He captured three natives and began to torture them until they confessed that this was indeed true . There was no proof that the natives would attack the Spaniards during this festival, however, Alvarado would plan an attack first by following an old maxim by deciding that the person who would attack first would be successful in this attack . During the festival, the Spaniards came heavily armed and closed off every exit surrounding the courtyard so that no one would escape . This would happen during their last days in Tenochtitlan. . </P> <P> Nobles lined each side along the buildings of the city's main causeway, which extended about a league . Walking down the center came Moctezuma II, who had two lords at his side, one being his brother, the ruler of Iztapalapa . Cortés dismounted, and was greeted by the ruler and his lords, but was forbidden to touch him . Cortés gave him a necklace of crystals, placing it over his neck . </P>

What was the estimated population of the aztec empire in 1519