The Parthians, while  Statius Priscus is occupied in Armenia in 163, intervene in Osroene, a Roman client in upper Mesopotamia, just east of Syria, with its capital at Edessa.

They depose the country's leader, Mannus, and replace him with their own nominee, who will remain in office until 165. (The Edessene coinage record actually begins at this point, with issues showing Vologases IV on the obverse and "Wael the king" (Syriac: W'L MLK') on the reverse.)

In response, Roman forces are moved downstream, to cross the Euphrates at a more southerly point.

On the evidence of Lucian, the Parthians still hold the southern, Roman bank of the Euphrates (in Syria) as late as 163 (he refers to a battle at Sura, which is on the southern side of the river).

Before the end of the year, however, Roman forces have moved north to occupy Dausara and Nicephorium on the northern, Parthian bank.

Soon after the conquest of the north bank of the Euphrates, other Roman forces move on Osroene from Armenia, taking Anthemusia, a town southwest of Edessa.