The Spanish brought firearms, explosives, and steel weapons, the likes of which the Native Americans had never used or seen before. When they saw the Spaniards coming in with these, they feared them and hid from them. The Spanish also brought horses, pigs and cattle which ensured superiority against the Indians. The natives had no domesticated animals, so the impact of seeing men on horses had a vast psychological effect on them. Although the natives outnumbered the Spanish, they were not immune to diseases such as smallpox and measles that the Spanish brought with them. As a result, the number of Native Americans decreased due to the Natives becoming ill and dying before they could even attack. Because the Native Americans were semi-nomadic and lacked significant fortifications, they aided the Spanish by facilitating the conquest. A very important aspect was experience, the Native Americans were always civil to each other unlike the Spanish. The Spanish have a long history of warring with other rivals for religious or territorial reasons, and this has made them gain enough experience to be prepared and armed for the unexpected. Religion played an important role in the colonization of the Western Hemisphere. The goal of the Spanish monarchs was to convert the natives to Christianity. This goal was facilitated when the Spanish learned that "Native American religion was not all that different from the spiritual belief popular in Europe (p. 9)." An example of this is Hernán Cortés, who was welcomed by the Aztec emperor as they probably believed he was their returned God. In exchange, Cortés received gifts of silver and gold, and Cortés eventually conquered the Aztecs