[2][4] This gave the Roman emperor Trajan (r. 98–117) the pretext to invade the Parthian domain and take advantage of the ongoing civil war between Vologases III and Osroes I.

[5] Trajan even reached as far as the Persian Gulf, where he forced the Parthian vassal ruler of Characene, Attambelos VII, to pay tribute.

[6][7] Fearing a revolt by the Parthians, Trajan installed Osroes I's son Parthamaspates on the throne at Ctesiphon.

[6][8] During his expedition, Trajan captured a daughter of Osroes I, who remained a Roman captive until the peace treaty concluded between the two powers in 129.

[11] The weakened state of the western part of the Parthian Empire gave Vologases III (whose eastern domains were untouched) the opportunity to regain lost territory seized by Osroes I.