In early 1520, Spanish conquistador Hernan Cortez’ conquest of the Aztec Empire fared poorly. The Aztecs no longer thought he was a god and lost their fear of the Spanish guns, steel, and horses. Increasing Spanish demands of gold, food, and women grated on the Aztecs. Especially chafing was the ban on human sacrifice, which was central to Aztec religion and society. Just prior to initial Spanish contact, the Aztecs held a ceremony during which 80,000 captive men, women, and children had their hearts torn out and eaten. These ceremonies were held regularly, though those so large were reserved for special occasions. To the Aztecs, all of the ills that had befallen their empire and people since European contact were due to the Spanish prohibition on human sacrifice. The Aztecs felt the gods were punishing them since they couldn’t be appeased with human blood.

Exacerbating the volatile situation with the Aztecs was Cotrez’ problems with the Spanish governor of Cuba. Their relationship had deteriorated to the point where the governor sent an expedition to arrest Cortez. Cortez was forced to leave the Aztec capital, Tenochtitlan, to confront the interlopers.

Tenochtitlan was one of the largest cities in the world with a population of over a million. Tenochtitlan by all accounts was absolutely massive, easily larger than the largest European cities at the time, London and Constantinople, both of which topped out at 200,000. Tenochtitlan was even larger before the mumps epidemic (which one of Cortez’ men brought in 1519) that killed about 100,000. Cortez’ kept a tenuous hold on the city with just a few thousand conquistadors and non-Aztec Indian allies.

Cortez left a subordinate to maintain the delicate relations with the Aztecs, while he left the city to deal with the governor’s expedition. Cortez managed to coopt his would-be captors, but he lost Tenochtitlan while he was away. In his absence, the lieutenant whom he left in the capital had arbitrarily slaughtered some Aztec nobles. Their deaths were the final humiliations. The entire city rose against the Spanish. The Aztecs swarmed the conquistadors, despite their technological advantage. The Spanish had harquebuses, crossbows, pikes, halberds, steel breastplates, small cannon, dogs of war, and armored knights on horseback – the very best of early 16th century military technology to fight the Stone Age equipped Aztecs. Dismissing the odds, the 1000 conquistadors in Tenochtitlan killed 30 for every loss. Nonetheless, the Aztecs still came on. The remaining 200 conquistadors were besieged in the emperor’s palace with the Aztec emperor, Montezuma, held captive.

Cortez heard of the news as he returned to Tenochtitlan. He had 1200 conquistadors and 3000 Tlaxalan allies recruited from one of the many Aztec enemies in the region. Cortez felt it was enough to chastise the Aztecs. He entered the city and the Aztecs allowed him to make it to the palace. They then closed the causeways behind him. Montezuma attempted to parley with the besiegers but the Aztecs had had enough. The Aztecs disavowed their emperor, denounced him a traitor, and killed him.

The next day Cortez sent 400 conquistadors to break out. Although the Aztecs took 20,000 casualties, all 400 Spaniards were killed or captured. Cortez was trapped.

On the night of 30 June/1 July 1520, the Spaniards attempted to sneak out, but they were spotted by an old woman fetching water. Soon the city descended upon the expedition and a running battle was fought through the streets. The Aztecs destroyed the causeways to trap the conquistadors but the Spanish filled the gaps with dead Aztecs and crossed over the bodies. The Aztecs disregarded the losses and continued to attack, especially targeting the stragglers. Cortez gave permission for each man to take as much gold as he could carry and the greedy ones were the first to die when they couldn’t keep up. The more gold the individual conquistadors took, the less likely they were to loie to spend it.

Cortez’ entire expedition would have been wiped out but the Aztec way of war centered on capturing not killing. They kept trying to take the Spaniards captive in order to sacrifice and eat them later, particularly Cortez. The Aztecs knew that without his leadership the expedition would have certainly broke up. But each time he was swarmed and hauled off, his men charged and rescued him. Despite grievous losses, the Spanish reached the mainland where the conquistadors could finally unleash the full power of their armored knights. The final charge by the last 20 knights routed the blocking Aztec force of 40,000. The thundering horsemen cut down every warrior with many colorful plumes, a symbol of Aztec status, eventually killing their commander. Only about 250 conquistadors and 1000 Tlaxalans managed to escape what the Spanish would call “La Noche Triste” or “The Sad Night”.

The next morning, the Aztecs resumed their practice of human sacrifice, and many a Spanish and Tlaxalan heart was consumed by the jubilant Aztecs.

The Aztecs would not enjoy their victory for long though. One of the conquistadors who arrived to arrest Cortez eventually joined with him. This particular conquistador was killed on a causeway during La Noche Triste. He fell behind, not because he carried too much gold, but because he was sick and weakened. He had smallpox.

The resulting smallpox epidemic caused by this initial vector killed 250,000 Aztecs in the coming months. When Cortez returned, he found the Aztecs of Tenochtitlan much easier to reconquer.