From the Annals of the Conquistadors – In 1520, Hernan Cortes, his army and Tlaxcalan allies were forced to flee Tenochtitlan in what became known at the Noche Triste. The population of Tenochtitlan had risen against them after Pedro Alvarado had slaughtered many Aztec nobles in a brutal and senseless massacre that occurred while Cortes was away quelling a rebellion of Spanish troops on the coast. Upon his return to Tenochtitlan, Cortes quickly realized that their position was untenable and ordered an evacuation from the island capital.
Under cover of darkness, the Spaniards and their allies set out for the mainland via the causeway to Tlacopan. The retreat was hampered by the fact that the Aztecs had removed the bridges over the gaps in the causeways that linked the city to the mainland. However, Cortés’ men constructed a portable bridge with which to cross the openings.They placed the portable bridge in the first gap, but at that moment their movement was detected and Aztec forces attacked, both along the causeway and by means of canoes on the lake. The Spaniards had no choice but to continue to retreat down the narrow causeway.
The retreat quickly turned into a rout as Cortes’ men could not remove the portable bridge unit from the first gap. The bulk of the Spanish infantry, left behind by Cortés and the other horsemen, had to cut their way through the masses of Aztec warriors opposing them. Many of the Spaniards, weighed down by their armor and booty, drowned in the causeway gaps or were killed by the Aztecs. Much of the wealth the Spaniards had acquired in Tenochtitlan was lost. More than two-thirds of the Spanish troops were killed or captured and the Spanish allies suffered heavy losses. Upon reaching the mainland at Tlacopan, Cortes wept over their losses. The old tree (“El árbol de la noche triste”) where Cortés cried is still a monument in Mexico.