Though Moctezuma followed Cortés' instructions in continually assuring his subjects that he had been ordered by the gods to move in with the Spaniards and that he had done so willingly, the Aztecs suspected otherwise.

Under constant attack, with gunpowder, food, and water in short supply, Cortés decided to break out of the city by night.

In order to put the Aztecs off their guard, he sent messengers asking for a one-week ceasefire, at the end of which the Spaniards would return any treasure of which they were in possession and would be permitted to leave the city peacefully.

This invitation would lead to the demise of many soldiers who, overburdened with treasure, found it impossible to navigate the causeways and other obstacles encountered on the way out of the city.

Cortés selected the western causeway to Tlacopan, needing the quickest route out of Tenochtitlan with all his provisions and people.

The causeway was apparently unguarded, and the Spaniards made their way out of their complex unnoticed, winding their way through the sleeping city under the cover of a rainstorm.

[2]: 298, 305  [discuss] The alarm was then shouted by others, first by a woman drawing water, and then by the priest of Huītzilōpōchtli from atop Templo Mayor.

[3][5]: 85 As the alarm spread, numerous Aztec warriors, noblemen and commoners alike, emerged from their houses and began attacking the Spaniards at every direction from their canoes or on the causeway with macuahuitl swords, spears, arrows, and stones thrown from slings.

As the Spaniards and their native allies reached the causeway, hundreds of canoes appeared in the waters alongside to harry them.

Amid a vanguard of horsemen, Cortés pressed ahead and reached dry land at Tacuba, leaving the rest of the expedition to fend for itself in the treacherous crossing.