Spanish conquistadores defeat a larger Aztec army at the Battle of Otumba.

Conquistadors or conquistadores were Spanish and Portuguese colonizers who explored, traded with and colonized parts of the Americas, Africa, Oceania and Asia during the Age of Discovery. Sailing beyond the Iberian Peninsula, they established numerous colonies and trade routes, and brought much of the New World under the dominion of Spain and Portugal.

The Aztec Empire, also known as the Triple Alliance or the Tenochca Empire, was an alliance of three Nahua city-states: Mexico-Tenochtitlan, Tetzcoco, and Tlacopan. These three city-states ruled that area in and around the Valley of Mexico from 1428 until the combined forces of the Spanish conquistadores and their native allies who ruled under Hernán Cortés defeated them in 1521. Its people and civil society are historiographically referred to as the Aztecs or the Culhua-Mexica.

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. It took place on July 7, 1520, in Temalcatitlán, a plain near Otumba during the development of the Conquest of the Aztec Empire. The result of the battle was a victory for the Spanish, which allowed Cortés to reorganize his army, having suffered casualties a few days before in the episode known as La Noche Triste. A year later, by reinforcing his army with new men and supplies, and creating alliances with the indigenous peoples who had been subjugated by the Aztec, Cortés managed to besiege and conquer Tenochtitlan.