Seleucia and Ctesiphon Captured; Parthamaspates Installed

The push down the twin rivers reached its apex in 116. Trajan crossed and recrossed the Tigris, and the two ancient cities—Seleucia on one bank, Ctesiphon on the other—fell. The river ran the color of hammered bronze in the afternoon light as Roman standards, scarlet against the dust, entered capitals whose names were older than Latin verse [3][17].

Cassius Dio lists the captures in his concise style: Seleucia taken, Ctesiphon taken, trophies displayed. Trajan moved to install a client king, Parthamaspates—rex Parthis datus—as the human instrument of Roman order in Parthia. It was a textbook move: convert conquest into control via a local face [3].

The visual tableau must have felt like the Column’s scenes in life: rivers bridged, councils held, promises exchanged. Coinage would later add PARTHICVS to Trajan’s titles, acknowledging the feat. For one season, the mapmakers could shade Mesopotamia as Roman, and envoys would write accordingly [14][15].

But even amid celebration, the mechanism’s strain showed. Seleucia and Ctesiphon are landmarks, not anchors. The supply line back to Antioch ran long and, after the earthquake, less sure. Client kings are only as stable as the garrisons behind them. The sound beneath the cheers was the creak of a system at full extension [3].

Still, in 116, the empire reached furthest. The Danube lay pacified; Arabia’s road ran smoothly; the Forum in Rome glittered. Trajan had, in Cassius Dio’s balanced phrase, expended “vast sums on wars and vast sums on works of peace… he drained no one’s blood for any of these undertakings” [3]. The question was whether the sums could continue to add up.