The Aztec Empire is among the most talked about Mesoamerican societies. The prominent empire spanned between 1325 and 1521 CE and covered a significant portion of the modern-day regions of central and southern Mexico. While historians refer to the inhabitants as the Aztecs, they did not use this term to refer to themselves. Instead, they called themselves the Mexica. That said, the Aztec Empire utilized a mix of military might and diplomatic deliberations to maintain control over its vast territories.The Rise of the Aztec EmpireCelebrations held for the coronation of emperor Moctezuma II of Mexico in the Durn Codex, 1579. Source: Bibliotexa Digital HispanicaThe Aztec Empire rose in 1428 under the leadership of Itzcoatl. This was after the community formed an alliance with the Tacubans and Texcocans to defeat the Tepanecs, their most formidable rivals in the region. Montezuma was Itzcoatls successor. He took over leadership in 1440 and was revered as a great warrior. Today, he is widely regarded as the father of the Aztec Empire.The Aztecs expansion model allowed the empire to rule over 500 small states by the early 1500s. Its population is estimated to have been between 5 and 6 million people at its height with Tenochtitln, its biggest city, having about 140,000 inhabitants. That said, the Aztec civilization also had highly developed social structures. Its society was based on a strict caste system made up of nobles at the top and slaves and serfs at the bottom.The Aztec Empire and Its Vast TerritoriesMap of Tenochtitlan from Nuremberg. Source: Library of the University of British ColumbiaWhile the Aztec Empire grew due to its conquest of neighboring regions, the expansion came at a cost. This is because the Aztec military gained power by adding men supplied by allied and defeated states. The large numbers of warriors allowed the Aztecs to easily subdue their enemies and gain new territory. With each victory, Aztec rulers demanded payment from defeated populations and took prisoners back to Tenochtitln to be used as human religious sacrifices. The religious sacrifices angered other tribes and caused numerous uprisings. Although Montezuma squashed many of the rebellions, the constant conflicts weakened the empire.This problem enabled Spanish invaders led by Hernn Cortes to form partnerships with other native people, most notably the Tlaxcalans, who were enemies of the Aztecs. The Tlaxcalan army contributed to the Aztecs downfall by helping Cortes attack the Aztecs.European Invasion of the Aztec EmpireThe Meeting of Corts and Montezuma by Unknown, ca. 1650. Source: The Library of CongressThe first European to visit Mexican territory was Francisco Hernandez de Cordoba. He arrived in Yucatan from Cuba with several ships and about 100 men in early 1517. Cordobas accounts of the Aztec region on his return to Cuba are believed to have compelled Diego Velasquez, the Spanish governor, to send a large contingent of soldiers back to Mexico under the command of Hernn Cortes. Subsequently, in March 1519, Cortes arrived at the town of Tabasco with about 500 soldiers. It was while there when he learned from the natives about the great Aztec Empire ruled by Moctezuma II.After the Spaniards gained the support of the local Indians, Cortes was able to create a base at La Villa Rica de la Vera Cruz, now Veracruz, Mexico. He then moved west toward the Aztec capital. Initially, the Spaniards were welcomed and met with gifts from Montezuma. However, Cortes intention was to take over Tenochtitln due to its gold and rich economy.The Empires DownfallArtists rendering of the Templo Mayor in Tenochtitlan, unknown artist, 1900. Source: Wikimedia CommonsUnfortunately for the Aztec people, the Spanish invaders brought with them some deadly diseases when they arrived such as smallpox, and the Aztecs had no resistance to many of the European diseases. As a result, smallpox spread among the indigenous people and with time devastated the population. It is estimated that half of Tenochtitlns inhabitants died from the disease.Illustration of smallpox from Dr. John D. Fishers Description of the Distinct, Confluent, and Inoculated Small Pox, Varioloid Disease, Cox Pox, and Chicken Pox, 1836. Source: Connecticut Explored or Google BooksAs such, when the Spanish first attacked the Aztecs in February 1519 following a series of misunderstandings, the kingdom was greatly weakened. The lack of superior weaponry also contributed to the downfall of the Aztec Empire. While the Aztecs outnumbered the Spaniards, their weapons were no match for Spanish arms. The Spaniards possessed guns and cannons while the Aztec warriors fought using wooden shields, bows, and spears. The situation put the Aztecs at a great disadvantage in times of conflict.Eventually, Cortes made Montezuma his prisoner and forced him into the role of a puppet king. Montezuma later on died in captivity on June 29, 1520. The Spanish led by Cortes shut down the Aztec resistance on August 13, 1521. About 240,000 people are believed to have died in the Battle of Tenochtitlan which ended the Aztec Empire. After his victory, Cortes burned down Tenochtitlan and built Mexico City where the city once stood.