Cortez's Campaign Against Aztec Empire

In his campaign against the Aztec Empire, Cortez relied upon the other local indigenous tribes for assistance. Why did they ally themselves to Cortez and how did they help him secure ultimate victory?

In Cortez’s venture to seize Mexico from the Aztec powers he was given he allied with other indigenous tribes, such as the Tlaxcalan's. It can be seen that perhaps the ally was more of mutual want for the destruction of the Aztecs as a mutual enemy rather then the want to benefit one another but the result shows us that this ally between the indigenous and the Spanish Hernan Cortez resulted in both the siege of Mexico and downfall of the Aztecs which may not have happened without this alignment.

After the Treaty of Torsedillas, Spain came to

Cortez left, Captain Pedro Alvarado in charge, along with 200 of his men and left Tenochtitlan with the rest to battle Narvaez, although Cortez’s army smaller, he was able to overthrow Narvaez and convince him to ally with them too instead of fighting against him. However whilst he had been away Alvarado had become subject to a revolt due to a massacre during one of the religious ceremonies/festivals for the Aztecs. Alvarado had begun killing prominent members of the upper classes of the Aztecs in turn setting off a local rebellion. Cortez insisted that Moctezuma speak and reason with his people but this only resulted in the crowd throwing stones etc. at him and resulting in his death. In the wake of his death a new leader was chosen by the people, Cuitlahuac, whose primary goal was to overthrow the Spanish power. Cortez no longer had control of Tenochtitlan or its inhabitants. The reality became pertinent to Cortez, although having the support of the Tlaxcala’s, the pure numeric superiority of the Aztecs was threatening and that fleeing or death seemed the only plausible end results. With this coming to a head on June 30th, 1520 “La Noche Triste” the night of sadness. Upon Cortez and his army inclusive of Tlaxcala allies trying to leave the city of Tenochtitlan, came upon vicious fighting and opposition from the Aztecs, resulting in the death of 450 Spaniards and thousands of Tlaxcala’s upon trying to flee Tenochtitlan. Despite the deaths the allies managed to flee despite being perused by the Aztecs, being allied with the Tlaxcala’s again being able to benefit Cortez and his men by guiding them out. By the end of this endeavor a troop that left Tenochtitlan with roughly 1,250 Spaniards finally arrived in Tlaxcala territory, widdled down to