The Antonine Plague

165–180 CE — Roman Empire, Rome

Today: Across the Roman Empire

At the height of Rome's power, soldiers returning from a war in the east carried home a devastating plague — probably smallpox — that swept the empire and killed millions, likely including an emperor. It thinned the army and the tax base at the worst possible moment, marking the point where Rome's long confidence began to curdle into strain. Disease had struck a superpower not at its edges but through its manpower and its tax base, the two things holding it together.

Worth knowing: The physician Galen described this plague in such detail that it's sometimes called the 'Plague of Galen' — and his writings then shaped Western medicine for the next 1,500 years.

Pattern: Pandemic — A pathogen spreads through a population and reshapes its demography, economy, and beliefs at once.

Entry 77 of 240 in Precedent, a walk through the whole human story in order.