The Roman–Parthian War of 58–63 or the War of the Armenian Succession was fought between the Roman Empire and the Parthian Empire over control of Armenia, a vital buffer state between the two realms. Armenia had been a Roman client state since the days of Emperor Augustus, but in 52/53, the Parthians succeeded in installing their own candidate, Tiridates, on the Armenian throne.
These events coincided with the accession of Nero to the imperial throne in Rome, and the young emperor decided to react vigorously. The war, which was the only major foreign campaign of his reign, began with rapid success for the Roman forces, led by the able general Gnaeus Domitius Corbulo. They overcame the forces loyal to Tiridates, installed their own candidate, Tigranes VI, on the Armenian throne, and left the country. The Romans were aided by the fact that the Parthian king Vologases was embroiled in the suppression of a series of revolts in his own country. As soon as these had been dealt with, however, the Parthians turned their attention to Armenia, and after a couple of years of inconclusive campaigning, inflicted a heavy defeat on the Romans in the Battle of Rhandeia.
The conflict ended soon after, in an effective stalemate and a formal compromise: a Parthian prince of the Arsacid line would henceforth sit on the Armenian throne, but his nomination had to be approved by the Roman emperor. This conflict was the first direct confrontation between Parthia and the Romans since Crassus' disastrous expedition and Mark Antony's campaigns a century earlier, and would be the first of a long series of wars between Rome and Iranian powers over Armenia.