Cortés studied unsuccessfully to be a lawyer at Salamanca, then in 1502 decided to try his luck in the new Spanish colonies in the New World. He took part in the conquest of Hispaniola and Cuba and was granted a large estate of land and slaves for his efforts. Expeditions to Yucatan by Francisco Hernandez de Cordoba in 1517 and Juan de Grijalva in 1518 returned to Cuba with small amounts of gold, and tales of a more distant land where gold was said to be abundant. Cortés eagerly sold or mortgaged all his lands to buy ships and supplies and arranged with the Governor of Cuba to lead an expedition, officially to explore and trade with the rumored new lands to the west.
In 1519 Cortés set out from Cuba with 11 ships, 500 men, and 15 horses. After short stops in Yucatan where he did not linger because there was little gold, he landed his party near Veracruz on March 4. The local Cempoala greeted him with gifts of food, feathers, and gold, and told that the land was ruled by the great lord in the city of Tenochtitlan. Soon ambassadors from the Aztec emperor Moctezuma II arrived with additional gifts. Cortés learned that he was suspected of being Quetzalcoatl or an emissary of Quetzalcoatl, a legendary man-god who was predicted to one day return. Cortés, aided by the advice of his native translator La Malinche, decided to take advantage of the Quetzalcoatl myth. While some of the expedition wanted to get such gold as they could quickly by trade or theft and then return to Cuba, Cortés had grander plans. He ordered all his fleet except for one small ship be burned, effectively stranding the expedition in Mexico. Cortés then lead his band inland towards Tenochtitlan.
Cortés arrived at the small independent state within the Empire, Tlaxcala, which attacked his troops, but the Spanish crossbow, steel sword, horses, and firearms quickly won the battle. Cortés said that if the Tlaxcalans would become his allies and servants he would forgive their disrespect, otherwise he would kill everyone in their entire nation. The Tlaxcalans agreed; Cortés then continued his march with some 2,000 Tlaxcalan ally soldiers and perhaps as many more Tlaxcalans carrying supplies.
After Cortés arrived in Cholula, the second largest city of the empire, he heard a rumor that the locals planned to murder the Spaniards in their sleep. Although he did not know if this was true or not, Cortés ordered a preventive strike. The Spaniards seized and killed the local nobles, set fire to the city, and killed an estimated 15,000 to 30,000 of the inhabitants. Cortés then sent a message ahead to Moctezuma that the lords of Cholula had treated him with disrespect and had to be punished, but if Moctezuma treated him with respect and gifts of gold, the Aztecs would not need to fear his wrath.
The expedition arrived in the Aztec capital November 8, 1519. Moctezuma had Cortés welcomed to Tenochtitlan with great pomp as would befit a returning god. Moctezuma had the palace of his father Axayacatl prepared to house the Spanish and their allies. Many of the Spaniards remarked that Tenochtitlan was the most magnificent city they had ever seen. Cortés demanded more gifts of gold, and that Moctezuma pledge to send similar large amounts of gold to Cortés and to the King of Spain each year forever after. Cortés also demanded that the idol be removed from one of the two largest temple pyramids in the city, and a shrine to The Virgin Mary be set up in its place. All his demands were met.
After some weeks in Tenochtitlan, however, the Spaniards noticed that they were being treated less and less like gods. Cortés seized Moctezuma and made him his prisoner as insurance against Aztec revolt. While this worked for a while, to Cortés's surprise he found that the Aztecs elected a new emperor, Cuitlauac, who ordered his soldiers to surround the palace housing the Spaniards and Moctezuma. Cortés ordered Moctezuma to speak to his people from a palace balcony and convince them to let the Spanish return to the coast in peace. Moctezuma was jeered and stones were thrown at him injuring him badly, and Moctezuma died a few days later.
The Aztecs seemed content to wait until the surrounded Spanish party ran out of food. On the night of July 1, 1520 Cortés decided to try to break out. The fighting was fierce, and many of the Spaniards were hindered by having loaded themselves down with as much gold as they could carry. Over 400 of the Spaniards and some 2,000 Indian allies were killed, but Cortés and a small portion of his party managed to fight their way out of Tenochtitlan and escape.
On his way back to the coast Cortés was met by a much larger party of Spaniards who had been sent by the Governor of Cuba to arrest Cortés for disobeying orders. However when Cortés told them of the vast amounts of gold in Tenochtitlan, they agreed to join Cortés. They then began the siege of Tenochtitlan, aided by the Tlaxcalans and many other Indian allies who had no love for the Aztecs who had been dominating them and who hoped to gain favor with the Spanish.
After a long siege and fierce fighting which destroyed almost the entire city of Tenochtitlan and killed some 120,000 to 240,000 Aztecs, the last Aztec emperor, Cuauhtémoc, surrendered to Cortés on August 13, 1521.
Cortés took part in one more expedition, through Guatemala to Honduras, then served a term as Governor General of "New Spain" (as Mexico was then called). He returned to Spain a very wealthy man. When asked what the new land was like, he crumpled a piece of parchment, then spread it out: "Like this."