The Spanish brought firearms, explosive weapons, and steel weapons, none of which the Native Americans had ever used or seen before. When they saw the Spaniards coming with them, they feared them and hid from them. The Spaniards also brought horses, pigs and cattle, which gave them superiority over the Indians. Native Americans did not have pets, so 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, which the Spanish brought with them. As a result, Native American numbers were decimated as the natives became sick and died before they could even attack. Since the Native Americans were semi-nomadic and lacked significant fortifications, they aided the Spanish by facilitating conquest. A very important aspect was having experience, the Native Americans were always civilized with each other, unlike the Spanish. The Spanish have a long history of war with other rivals over religion or territory, giving them 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 so 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 returning God. In return, Cortés received gifts of silver and gold and eventually Cortés conquered the Aztecs.