On the surface, the conquest of the Aztec empire by Herman Cortes is one of the most amazing military accomplishments in history. With a small fighting force numbering in the hundreds, Cortes led the Spanish explorers into victory against an Aztec population that many believe topped 21 million. In light of such a seemingly impossible victory, the obvious question is: how did a small group of foreign fighters manage to topple one of the world's strongest, wealthiest, and most successful military empires?
Several factors led to Cortes' success. First, the Spanish exploited animosity toward the Aztecs among rival groups and convinced thousands of locals to fight. In one account of a battle, it is recorded that at least 200,000 natives fought with Cortes. Next, the Spanish possessed superior military equipment in the form of European cannons, guns, and crossbows, leading to effective and efficient disposal of Aztec defenses. For example, Spanish cannons quickly defeated large Aztec walls that had protected the empire against big and less technically advanced armies.
Despite the Spanish advantages, the Aztecs probably could have succeeded in defending their capital city of Tenochtitlan had they leveraged their incredible population base to increase their army's size and ensured that no rogue cities would ally with Cortes. In order to accomplish this later goal, Aztec leader Motecuhzoma needed to send envoys to neighboring cities telling their inhabitants about the horrors of Spanish conquest and the inevitability of Spanish betrayal.
In addition, the Aztecs should have exploited the fact that the battle was taking place on their territory. No reason existed for the Aztecs to consent to a conventional battle, which heavily favored the Spanish. Motecuhzoma's forces should have thought outside the box and allowed Cortes into the city, only to subsequently use hundreds of thousands of fighters to prevent escape and proceed in surprise "door-to-door" combat. With this type of battle, the Aztecs would have largely thwarted Spanish technological supremacy. However, in the end, the superior weaponry of the Spanish, the pent-up resentment of Aztec rivals, the failure of Aztec diplomacy, and the lack of an unconventional Aztec war plan led to one of the most surprising military outcomes in the past one thousand years.