The Kingdom of Armenia

Armenia was not, strictly speaking, a Parthian sub-kingdom, though it did, eventually, end up with an Arsacid dynasty. Armenia first came into the Parthian orbit during the reign of Mithradates II, who defeated Artavasdes and took his eldest son, Tigranes II(later called "the Great") as hostage. At the death of Artavasdes in 94 BC, Tigranes was placed on the Armenian throne by Mithradates II in exchange for territory. Tigranes was then invited by the Syrians to take the Seleucid throne (83 BC). Upon the death of Mithradates II, Tigranes turned on the Gotarzes I and reclaimed the land he lost plus additional lands including Atropatene and Gorduene. This resurgence of Armenian independence was short lived however, as Tigranes angered both the Romans and the Parthians. Lucullus and Pompey put an end to Tigranes' dreams of empire. Tigranes' son and succesor was forced to walk a fine line between the Romans and the Parthians in order to maintain his life and his throne. The kingdom of Armenia became one of the central bones of contention between Rome and Parthia and generally sided with whomever appeared to be the strongest. By the time of Nero the mutually acceptable method for choosing a successor to the Armenian throne was for the Parthians to name the candidate and for the Romans to crown him, thus ensuring that both sides were satisfied with the king.This method worked well, as long as the Romans and Parthians were interested in peace, but the choice of succesors to the Armenian throne became the pretext for several Roman invasions of both Armenia and Parthia. By this means the Armenians acquired an Arsacid dynasty with the accesion of Tiridates, brother of Vologases I, in 66 AD, which was to last down to the 5th century AD, well after the fall of the Parthian empire and the senior Arsacid line.