In the year 52 CE, the Parthian king Vologases I invaded Armenia, occupied its capital Artaxata, and made his younger brother Tiridates king of Armenia.note[Tacitus, Annals 12.50.] This was a breach of a treaty that the Parthian king Phraates IV had concluded with the Roman emperor Augustus in 20 BCE: the Romans were allowed to appoint the Armenian king. Vologases immediately got the problems he had been asking for.
In Media and Hyrcania, his son Vardanes II revolted and it is certainly possible that he had Roman support.note[Tacitus, Annals 13.7.] Vologases' supply lines were now threatened, and to make problems worse, the Armenian winter turned out to be severe. As a consequence, an epidemic broke out,note[Tacitus, Annals 12.50.] and Vologases returned home.
We do not know how Vardanes' reign ended, but to judge from the coins minted in Ecbatana, it lasted some four years. According to the Roman historian Tacitus, the suppression of the Hyrcanian revolt required numerous campaigns.note[Tacitus, Annals 15.1.]
The chronology of the Arsacid kings of the Parthian Empire is less well-understood than, for example, the sequence of Seleucid and Ptolemaic kings or the emperors of Rome. This information is based on the researches by G.R.F. Assar, as published in "Iran under the Arsakids, 247 BC – AD 224/227" in: Numismatic Art of Persia (2011).