The conquest of the Mexico by Spanish had started with conquest of the Aztec Empire In 1519. After exploration of the Americas by Columbus, Spanish organized expeditions for discovery and colonization of new areas in the new continent. In battles between Aztec Empires Spanish Conquistadors made allies with local kingdoms and tribes such as Confederacy of Tlaxcala and many others. The population of Aztecs Empires was over 25 million when Spanish had arrived the continent, but after 30-40 years it dropped to as few as 1 million due to killings and epidemics of illness that of the Indigenous people lacked immunity. Several epidemics took place during those years, among these; there were terrible one causing over 8 million death. After conquest of Aztec Empire, Spanish didn’t stop colonization. They discovered new areas; killed more massacred more people, caused new epidemics. Between the years 1519 and 1635, Spanish were responsible over 20 million deaths in the area of Mexico. This death toll doesn’t include the Conquest of Peru or Yucatan and many other areas only Mexico. If we count total death caused by Conquest of Americas, it would be over 100 million. According to many historians the population of the indigenous people was one third of the world’s population. Nowadays, their number is too few.