The Aztec at this time was a thriving civilization. When Hernan Cortes heard that there were some difficulties in the Aztec politics, he took his crew to the interior of Mexico. On his way, he came into contact with local Indians. When he told these Indians his purpose to conquer the Aztec, these Indians became his allies. Montezuma II, the ruler, tried to buy Cortes off, but it didn't work. Montezuma expected the Spaniards to be envoys of a god who was expected to arrive in 1519 ("One Reed Year"). Knowing this, the Aztecs treated Cortes with great honor and Cortes siezed he opportunity. He took Montezuma II hostage. He left Tenochtitlán to do something, but when he came back, the Aztecs were rebelling. Due to the lack of food, Cortes had to lead his men out of the city. During their retreat, Cortes and his crew defeated a large army at Otumba. In 1521, Cortes returned to Tenochtitlán, and the city fell after a 3-month siege.