Political map of Europe & the Mediterranean 19 October 113 (Outbreak of Trajan’s Parthian War): In c.109 yet another civil war broke out in Parthia, with Shah Osroes I (Osroes I of Parthia) gaining control of the west of the empire and Vologases III (Vologases III of Parthia) the east. The following year Osroes installed his nephew Axidares as king of Armenia (Axidares of Armenia), but failed to consult the Romans beforehand and thus violated the Treaty of Rhandeia (63 AD). Despite Osroes’ apologies, Trajan took this as a pretext for war, marching on the eastern frontier in 113 (Trajan's Parthian War).