Cortes and his men had advanced weapons that the Aztecs had never even seen or heard of in their life. He started recruiting troops from people that the Aztecs had taken over. During the first battle, even though they killed Montezuma, the Spanish were outnumbered. Before they could attack again, there was a 2nd attack, smallpox. This killed hundreds of warriors. In 1521, the Spanish destroyed the Aztec capital , Tenochtitlan.