By June 1520 Hernán Cortés’s improbable position in Tenochtitlan had collapsed. The Spaniards had lived eight months inside the Aztec capital as guests-turned-captors of the emperor Moctezuma II; while Cortés was away on the coast defeating a rival Spanish expedition, his lieutenant Pedro de Alvarado had massacred the celebrants of the festival of Toxcatl in the sacred precinct, and the city had risen. Cortés fought his way back in to find his garrison besieged. Moctezuma, sent to the rooftops to calm his people, was met with stones and arrows and died days later — by Spanish account of his wounds, by native tradition strangled by his guests, now that he was useless. The causeways were cut, the bridges removed, and perhaps 200,000 people surrounded roughly 1,200 Spaniards and a few thousand Tlaxcalan allies.
The causeway
Cortés chose to break out at midnight on 30 June 1520, in rain, over the shortest causeway west to Tlacopan, carrying a portable bridge to span the gaps. First the royal fifth and then the rest of the accumulated treasure was laid out; each man took what he chose. The veterans of Bernal Díaz’s account took little. The newcomers stuffed their clothes and armour with gold.
The column was discovered mid-crossing — a woman drawing water, by tradition, raised the cry — and the lake filled with war canoes. The portable bridge jammed in the first gap under the weight of the retreat. At each further breach the fighting rear pushed the column into the water, until the gaps were bridged by drowned horses, baggage, and men. Those who fell burdened with gold sank; those taken alive were reserved for sacrifice. Perhaps 600 or more Spaniards died that night — some accounts run far higher — along with several thousand Tlaxcalans, most of the horses, all the artillery, and nearly all the treasure, which went to the bottom of Lake Texcoco and has mostly never been found.
Tradition — first written long after — has Cortés sitting beneath an ahuehuete cypress at Tlacopan and weeping among the survivors: la Noche Triste, the Sad Night. The tree, el Árbol de la Noche Triste, stood into modern times and its burnt trunk still has an address in Mexico City.
Whose sad night?
The escape was not the end but the hinge: Cortés won the desperate battle of Otumba days later, reached Tlaxcala, and returned within a year — with brigantines, more allies than ever, and smallpox marching ahead of him — to besiege and destroy Tenochtitlan in 1521.
Mexico has lately revisited the name. In 2021, the quincentenary, Mexico City officially rechristened the commemoration la Noche Victoriosa — the Victorious Night — on the reasonable grounds that whether the night was sad depends entirely on which side of the causeway your ancestors stood.