For the Tlacaltecans, the alliance was a double edge sword, but it did help Cortes defeat the Aztec a bit easier. Why did the Tlacaltecans allied themselves with Cortes? The Tlaxcalans was poor and was lacking common things that they themselves could not get from trade because the Aztecs had put a commercial block on the Tlacaltecans, and add the fact that the Aztecs were using the Tlaxcalan as sacrifices to various Aztec gods, the Tlacaltecans were ready to just get rid of the Aztecs in any way they can. With that said, in chapter 8, using his new alliances, Cortes and his army, along with the Tlacaltecan warriors, matched to Cholula, which was under Aztec control. Cortes ordered an attack on the city, which killed more than 3,000 people, and burnt it down. With news of the massacre of Cholula spreading to neighboring Aztec cities and such, the cities themselves would just yield to Cortes he approached them so that they would not have to suffer the same fate of Cholula. This made it easy for Cortez to move on through to Tenoclitlan, because he was met with little to no resistance. .
In Chapter 11, Velázquez sends Panfilo de Narvaez with an army of his own to capture Cortes and bring him back to Spain to be trialed for his crimes. Hearing about this, Cortes knows that if he were to be captured, he would hanged for his crimes, rather than dying, he steps aside from his army in Tenoclitlan, bringing only a few soldiers and Tlacaltecan warriors. Using his the island's geography to his advantage, Cortes got the upper hand on Narvez and defeated Narvez during a surprise night attack. Keeping in mind that Narvaez had the numbers advantage, but was not prepared. Telling Narvaez and the defeated soldiers about Tenoclitlan and the gold it possessed, which was evidently nicknamed the city of gold (Whoo El Dorado), they agreed to join Cortes and capture the city with him. Cortes at this point had an army of hundreds, but ran into trouble when he got back to Tenoclitlan because under the leadership of Alvarado, he and the men attacked the Aztecs and killed some of the higher ups in the Aztec society.
