China Sea) in Ptolemy's Geography. Continuation of Roman hostilities and Parthian decline After the Iberian king Pharasmanes I had his son Rhadamistus (r. 51–55 AD) invade Armenia to depose the Roman client king Mithridates, Vologases I of Parthia (r. c. 51–77 AD) planned to invade and place his brother, the later Tiridates I of Armenia, on the throne. Rhadamistus was eventually driven from power, and, beginning with the reign of Tiridates, Parthia would retain firm control over Armenia—with brief interruptions—through the Arsacid Dynasty of Armenia. Even after the fall of the Parthian Empire, the Arsacid line lived on through the Armenian kings. However, not only did the Arsacid line continue through the Armenians, it as well continued through the Georgian kings with the Arsacid dynasty of Iberia, and for many centuries afterwards in Caucasian Albania through the Arsacid Dynasty of Caucasian Albania. When Vardanes II of Parthia rebelled against his father Vologases I in 55 AD, Vologases withdrew his forces from Armenia. Rome quickly attempted to fill the political vacuum left behind. In the Roman–Parthian War of 58–63 AD, the commander Gnaeus Domitius Corbulo achieved some military successes against the Parthians while installing Tigranes VI of Armenia as a Roman client. However, Corbulo's successor Lucius Caesennius Paetus was soundly defeated by Parthian forces and fled Armenia. Following a peace treaty, Tiridates I traveled to Naples and Rome in 63 AD. At both sites the Roman emperor Nero (r. 54–68 AD) ceremoniously crowned him king of Armenia by placing the royal diadem on his head. A long period of peace between Parthia and Rome ensued, with only the invasion of Alans into Parthia's eastern territories around 72 AD mentioned by Roman historians. Whereas Augustus and Nero had chosen a cautious military policy when confronting Parthia, later Roman emperors invaded and attempted to conquer the eastern Fertile Crescent, the heart of the Parthian Empire along the Tigris and Euphrates. The heightened aggression can be explained in part by Rome's military reforms. To match Parthia's strength in missile troops and mounted warriors, the Romans at first used foreign allies (especially Nabataeans), but later established a permanent auxilia force to complement their heavy legionary infantry. The Romans eventually maintained regiments of horse archers (sagittarii) and even mail-armored cataphracts in their eastern provinces. Yet the Romans had no discernible grand strategy in dealing with Parthia and gained very little territory from these invasions. The primary