The Battle of Otumba was fought between the Aztec and allied forces led by the Cihuacoatl Matlatzincátzin and those of Hernán Cortés made up of the Spanish conquerors and Tlaxcalan allies, which took place on July 7, 1520, in Temalcatitlán, a plain near Otumba during the development of the Conquest of the Aztec Empire. Wikipedia