The Secret Weapon That Toppled the AztecsAn invisible killer brought down an empire.

From the show

Hidden Sides of History

History often credits Spanish weaponry for the fall of the Aztec Empire. But the decisive factor was a force the Aztecs couldn't see or fight: a devastating virus. The smallpox epidemic of 1520, introduced by the conquerors, swept through Tenochtitlán. It decimated the population, killed its emperor, and shattered the society's ability to resist, proving that microbes can be more powerful than armies.