The Aztecs had predicted their own fall. According to Aztec legend, a god named Qetzalcoatl had left their land and promised to return. when he did, the Aztec would fall. The god had had white skin and a long beard, much like Hernando Cortes, an spanish conquistador who arrived in Mexico in the year predicted to destroy the Aztec civilization. Some Aztecs didnt beleive the legend, but after they heard of Cortes they began to.
The real way Cortes managed to kill the Aztecs with 600 men was mainly because he didnt have 600 men. He had 600 spanish men, but he had over 75,000 men in total. As he traveled about Mexico, he had come across many tribes that hated the Aztec for conquering them and making them pay tribut in food, money and warriors. Cortez formed alliances as he travleled and his army grew from 600 to many thousand. along with all the Indians that hated the maya, he defeated them and took the city for his own. Another compnent to the defeat of the aztec are the diseases that the spanish brought from europe with them, such as smallpox. with the warriors dying, it was a bit easier to kill them off, number advantage aside.
First Cortez laid seige to tenichtitlan, since the aztec depended mainly on their conquored tribes for food, they starved mainly before they decided to give up and fight the losing battle.
 |  Here is a picture of the Aztec battle basically..the Spaniard and the Aztec warrior. |
