Sasanian Persia

224–651 CE — Persia, Sasanian Empire

Today: Iran and Iraq (capital Ctesiphon, near Baghdad)

The Sasanians rebuilt the Persian empire and spent four centuries as Rome's only equal — the two powers fought, traded, and exhausted each other along the same frontier for longer than the United States has existed. They made Zoroastrianism a state religion, ran a sophisticated bureaucracy, and one of their kings captured a Roman emperor alive. Their final war with Byzantium in the 600s left both empires bankrupt and depleted, at precisely the moment armies came out of Arabia.

Worth knowing: After capturing the Roman emperor Valerian in 260 CE, the Persian king had the humiliation carved into a cliff face, showing the emperor kneeling before him on horseback. The relief is still there.

Pattern: Imperial overstretch — A state's commitments outrun the resources and logistics needed to hold them; the margin fails first.

Entry 80 of 240 in Precedent, a walk through the whole human story in order.