Alliances with other tribes helped the Spanish, Malintzin, an Indian woman helped cortez; she helped him work with others who did not like paying tribute
Better Weapons, GUNS, also helped, (guns were acquired through trade in Europe, from China)
Spanish also brought horses; the Aztec had never seen horses
Geography was also hurtful, the Spanish blocked causeways, this cut off drinking water. Thousands starved
Finally, the Spanish brought smallpox, the Aztec could not fight disease and the Spanish

Causes of the Defeat of the Aztec