Cortez was a 16th-century explorer who crossed the sea with only a few hundred men and conquered the aztec empire. the aztecs mistakenly believed that cortez and his men were messengers from one of their gods. cortez captured the king,montezuma, and the land of the great city of tenochtitlan, which is now mexico city. unknown to both the spaniards and the aztecs, the spaniards had brought a powerful but invisible weapon with them across the sea: smallpox, which killed thousands of aztecs. because cortez had come from europe without permission from the spanish king, he was forced to flee once the king learned of his disobedience.