To the Core

Issue 1 · July 2026

Death by Microbe

How disease ended empires

Every one of these five pieces starts the same way: something too small to see, and an empire that didn’t see it coming. Malaria wearing down the ancient Mediterranean for centuries. A plague arriving in Athens by ship in 430 BCE, three years into a war Pericles thought he had a plan for. Bubonic plague reaching Constantinople in 542, while Justinian was still finishing the job of reuniting Rome. Smallpox travelling with the Spanish into a Aztec capital its own soldiers couldn’t have taken alone. Typhus, not the Russian winter, breaking Napoleon’s army before it ever reached Moscow.

None of these are stories about germs, exactly. They’re stories about what a civilisation looks like at the exact moment it turns out to have a body — walls that keep people in as easily as they keep enemies out, ports that move grain and also fleas, an army that is really just several hundred thousand people standing very close together. The empires in this issue didn’t fall to better armies. They fell to arithmetic: a pathogen doesn’t care how many battles you’ve won.

What ties history to biochemistry here is the same thing every time: the mechanism is small and the consequence is enormous. A bacterium that disables a single class of immune cell ends up deciding which language is spoken in the eastern Mediterranean for the next thousand years. A louse that can’t survive a wash ends up deciding who rules Europe in 1813. That gap — between the size of the cause and the size of the effect — is why this issue exists.

Co-editors — Naasha Mahadevia and Rhea Hiremath

Table of contents

  1. FIG. 1

    Can a disease take a thousand years to kill an empire?

    Not every civilisation-ending disease arrives with trumpets. Some take a thousand years.

  2. FIG. 2

    Did one plague end Greece's Golden Age?

    Pericles bet the city on its walls. The walls kept the Spartans out and the disease in.

  3. FIG. 3

    What stopped Justinian rebuilding Rome?

    Justinian had almost rebuilt Rome. Then a flea arrived on a grain ship from Egypt.

  4. FIG. 4

    Was it smallpox, not Cortés, that took Tenochtitlan?

    Cortés brought swords, horses and allies. The weapon that took Tenochtitlan was none of those.

  5. FIG. 5

    Did lice beat Napoleon before Russia did?

    600,000 men crossed the Niemen. 100,000 came back. The winter gets the credit; the lice did the work.