The Battle of Colhuacatonco was fought on 30 June 1521 during the late stages of the Siege of Tenochtitlan between Spanish-Tlaxcalan forces and the Mexica Empire (also typically referred as Aztec Empire). It is regarded as the most important victory achieved by the Mexica during the siege.
The battle was fought as a result of the Spanish soldiers growing dissatisfied with the lack of progress done during the siege thus far, as the Spanish-Tlaxcalan forces had failed to take any important amount of territory since the beginning of June. Captain Hernán Cortés of the Spanish decided to launch a massive assault onto the city to take the market of Tlatelolco. The Spanish faced a much stronger resistance than expected and were eventually forced to retreat, suffering their worst losses since La Noche Triste and the Battle of Otumba a year earlier.
Though much of the fighting occurred elsewhere in Tlatelolco, northern Tenochtitlan and Tacuba, the battle became known as such because most of the fighting occurred in this neighborhood; the Spaniards suffered their worst losses in this battle in this site.
The battle became famous among modern historians as a result of the Spanish defeat, which was perceived as humiliating and retroactively seen as a demonstration of indigenous resistance against colonialism even in the most dire circumstances, as by this point the city was already facing widespread starvation and disease and yet still achieved victory, though the battle did not stop the city from falling to the Spanish Empire in August of the same year. The battle also became famous because Cortés narrowly escaped death during the fighting, as he was captured by multiple Mexica warriors, who typically didn't spare their prisoners, before he was rescued.
Background
The siege of Tenochtitlan
In late April 1521, during the late stages of the Spanish Conquest of Mexico, the troops under the command of the Spanish captain Hernán Cortés began preparations to lay under siege the city of Mexico-Tenochtitlan, de facto capital of the Mexica Empire known today as Mexico City. In the 28th, 13 brigantines were launched from Texcoco and protected by thousands of war canoes from their allies to assert their dominance over Lake Texcoco, where the city was settled (though one of them was eventually scrapped due to its vulnerable size), and in May 22 they destroyed the Chapultepec aqueduct to cut the city's water supply. Mexico and Spain had been in a state of war since May 1520, and the Spanish were aided by an alliance with Tlaxcala, a nation which had been at war with Mexico for many years, which was formed in September 1519 and brought them thousands of warriors. They were also aided by many different cities and towns in the Valley of Anáhuac which allied the Spanish and Tlaxcalans as a result of their desire for aid against the empire's domination. Among the most important of these allies was Ixtlilxóchitl II, who was the de facto ruler of Texcoco since Cacamatzin's arrest in early 1520. He supplied the Spanish about 50,000 warriors who proved vital for the war effort, though his support for the Spaniards gave him a reputation of being a traitor among the Mexica. According to Cortés, by the time the Battle of Colhuacatonco took place the Spanish had an army of 150,000 indigenous warriors protecting them.
During this period, Cuauhtémoc was emperor since early 1521, being crowned after the sudden death of his uncle Cuitláhuac due to smallpox. Despite being no older than 25 years, his hatred towards the Spaniards and ability as a warrior made him a serious rival for the Spanish and Tlaxcalans. As the population of Tenochtitlan was being evacuated to Tlatelolco at the north of the city, Cuauhtémoc stationed his headquarters in the site of Yacacolco, in the calpolli (neighborhood) of Atenantitech, near the market of Tlatelolco.
Cortés then divided his troops to settle themselves into three garrisons to cut the resources of the city: one in Tlacopan (today known as Tacuba) at the west under the command of Pedro de Alvarado, another in Coyoacán at the southwest under Cristóbal de Olid, and the third and largest one in Iztapalapa at the south under Gonzalo de Sandoval. Cortés settled himself in Acachinanco, the point where the Iztapalapa causeway forks to Tacubaya and Coyoacán at the west and Iztapalapa, Mexicatzinco and Colhuacan at the south. By the early days of June, these positions had been successfully captured after the Spanish won various battles for control of the lake, the western parts of the valley and Iztapalapa. Sandoval was eventually relocated to Coyoacán, where he fought and defeated the local defenders, as Cortés joined forces with Olid, prepared his camp and set up a large iron cannon, one of the three the Spanish had available, for an assault. Everyday during this period various skirmishes were fought, both during the day and the night, as the Mexica raided the Spanish camps and the brigantines caused chaos and destruction across the city. Sandoval meanwhile, under the advice of Alvarado, decided to capture the northern causeway at Tepeyac and settled himself there, cutting off the last opening the city had, completing the blockade.
First assaults into the city The first major assault onto the city was carried out six days after Cortés settled in Acachinanco, going through the calpolli of Xoloco, in the campan (one of Tenochtitlan's four divisions) of Moyotlan at the south of the city. Using the heavy cannon and two brigantines, they managed to penetrate their way into the central plaza of the city, where they famously stormed the Templo Mayor, killing the priests on top. However, the Spanish were suddenly met with multiple war canoes from between the buildings and were forced to flee in a rush, abandoning the cannon, which the Mexica later pushed into the lake, as they retreated back to Acachinanco. Even then however, the Spanish cavalry proved very effective and killed many Mexica warriors and forced many others to retreat, which allowed the Spanish to get out more easily.
Though in this assault the Spaniards were eventually forced back, the fact that they broke their way into the heart of the city's capital despite the fierce resistance inside caught the attention of many peoples across the valley, and soon enough Cortés obtained more allies, such as the Chinampaneca (peoples from the south of the lake, including the Xochimilca, Mexicatzinca, Cuitlahuaca, etc.) and several Otomi tribesmen, who were highly skilled warriors.
Throughout the following assaults, the main tactic the Spanish used was to penetrate into the city, burn and destroy buildings and houses and filling gaps in the causeways to create more space for future assaults and attempt to destroy any monuments in the city that were possible to demoralize their enemy, and at the night they would return to their camps to safety. They soon destroyed their old barracks at the and the prestigious zoo built during the reign of Moctezuma II. However, everytime the Spaniards engaged in another assault they found that most of their progress had been undone; the Mexica were rebuilding whatever they could and creating new gaps in the causeways after each assault. The speed at which the Mexica undid the Spanish progress baffled Cortés, and it started to become clear that a new plan was needed to succeed. Cortés initially did not want to settle himself in the city itself, as that would've left the camps relatively unprotected and would've left him completely surrounded, but Alvarado and Sandoval became increasingly impatient with Cortés' tactic and eventually began to capture territory and create camps in the city itself.
One day however, in the middle of June, Alvarado, without consulting Cortés or receiving any aid from the other Spanish groups or indigenous allies, decided to perform a major assault to the market of Tlatelolco, an objective which was perceived as vital to achieve victory. The two or three Spanish brigantines under Alvarado landed in the site of Iyauhtenco, in the calpolli of Nonoalco, in western Tlatelolco, without indigenous allies. Noting their numerical advantage, the Mexica hid most of their troops within the buildings to perform an ambush. The intensity of the ambush forced the Spaniards to retreat back to their brigantines. Some Spaniards were captured and were then sacrificed. Though some records suggest that only four Spaniards were captured in this assault, indigenous records suggest the number to be as high as fifteen. Bernal Díaz del Castillo, a Spanish soldier who wrote a detailed chronicle on the war, suggested that five Spaniards were captured and two others were killed in the brigantines.
Cortés was upset at Alvarado for this reckless action, to the point that he personally sailed to Alvarado's camp to reprimand him, but noting how far he managed to get into Tlatelolco before being forced to retreat, some Spanish noticed that a large assault into Tlatelolco could result in a victory, as progress thus far had been very slow.
Tactics and strategies used in the siege
At its peak in June 1520, the Spanish army numbered over 1300 soldiers, 80 crossbowmen, 80 arquebusiers and 96 horses, but by the time the Spanish set their brigantines afloat the army had been reduced to 700 footmen, 86 horses and 118 crossbowmen and arquebusiers, along with 3 large cannons and 15 smaller ones. The numerical superiority of the Mexica was highly important, and thus the thousands of indigenous warriors who allied the Spanish played a crucial role in the war. Tenochtitlan, however, was not prepared for a siege like this; its enormous population largely relied on resources brought from other parts of the empire and it did not possess enough food storage to feed the entire population during sieges. Cortés's strategy was largely based on starving the city rather than conquering it through combat alone. Another advantage the Spanish had was their technological superiority; the Spanish brought weapons with them which completely challenged the traditional ways of Mexica combat. Their cannons, firearms and crossbows could easily disrupt Mexica formations on the narrow causeways with their superior power, thus challenging the Mexica troops in what would normally be an advantageous position with their numerical superiority.
To make matters worse for the Mexica, there had been a smallpox epidemic in the region since May 1520, since a few of the men under Captain Pánfilo de Narváez had the disease and, when Cortés convinced his men to join him after the Battle of Cempoala, they unintentionally carried it to Tenochtitlan. The indigenous population did not have immunity against this disease and millions died of it throughout the following years.