Europeans used the new geographical knowledge and navigational technique developed during the Renaissance to try to circumvent Muslim control of trade with China. They constructed the galleon, a new kind of ship that was capable of making the very long voyages. The Portuguese dominated the route down and around the tip of Africa. In 1492 Christopher Columbus sailed west hoping to find an alternate route. The Spanish explorers only gradually realized that they had found a new continent. Hernan Cortez was sent in 1518 from the island of Cuba to the mainland. He was supposed to build a settlement and establish trade with the Aztec Empire. Cortez had other ideas. Historians still argue over how small Spanish armies managed to conquer the Aztec and Incan Empires. Both diseases such as Smallpox, and the immense superiority of the Spanish steel weapons and armor, where significant factors. Another key factor was the highly stratified nature of the native society. Once the ruling class was defeated and co-opted, the Spanish were able to simply take over the work obligations imposed on the peasantry. Equally important was that the Spanish did not try to suppress the native aristocracy. They ruled through it, often marrying into it. Though ineffectual, the native population did offer perpetual resistance to Spanish rule for decades to come.