Parthian War; capture of Ctesiphon

With Lucius Verus in the East, the empire moved its weight to Syria. Antioch’s streets became headquarters; Seleucia on the Tigris, a target; Ctesiphon, the Parthian royal city, the prize. Legions from Cappadocia, Syria, and Armenia advanced along the Euphrates and through northern routes, timing river levels and supply trains with clockwork precision [18].

By 165–166, the Roman push reached its crescendo. Ctesiphon fell; Seleucia’s fate was harsh. The colors were the black of smoke and the bronze of legionary helmets; the sounds, drums and shouted Latin cutting across the sibilant local tongues. Standards that once stood by the Danube now cast shadows on the Tigris.

In Antioch, Lucius staged triumphal celebrations. In Rome, Marcus received messages written in a steady hand: objectives achieved, territories chastened. Yet along with booty and honor, returning troops carried something else—disease.

The campaign’s geography mattered. From Antioch to Ctesiphon and back by way of ports in Cilicia and Achaea, the army’s routes traced the empire’s arteries. Whatever rode those paths would be carried to Ostia and up the Tiber to Rome. In 166, as the last victories were counted and coin dies clattered, symptoms began to appear [18].

For a moment, though, the war looked like the usual Roman arithmetic: march, capture, celebrate. Then the sums changed.