legions, from Syrian Antioch to Armenia. The Artaxata army under Vologases IV' command surrendered to Roman general Priscus who installed a Roman puppet, Sohaemus (Roman senator and consul of Arsacid and Emessan ancestry), on the Armenian throne, deposing a certain Pacorus installed by Vologases III. As a result of an epidemic within the Roman forces, Parthians retook most of their lost territory in 166 and forced Sohaemus to retreat to Syria. After a few intervening Roman and Parthian rulers, Vologases II assumed the throne in 186. In 198 Vologases II assumed the Parthian throne and named his son Khosrov I to the Armenian throne. Khosrov I was subsequently captured by the Romans, who installed one of their own to take charge of Armenia. However the Armenians themselves revolted against their Roman overlords, and in accordance to new Rome-Parthia compromise, Khosrov I's son, Tiridates II (217–252), was made king of Armenia. Sassanids and Armenia In 224 the Persian king Ardashir I overthrew the Arsacids in Parthia and found the new Persian Sassanid dynasty. The Sassanids were determined to restore the old glory of the Achaemenid Persia, so they proclaimed Zoroastrianism as the state religion and considered Armenia as part of their empire. To preserve the autonomy of Arsacid rule in Armenia, Tiridates II sought friendly relations with Rome. This was an unfortunate choice, because the Sassanid king Shapur I defeated the Romans and made peace with the emperor Philip. In 252 Shapur I invaded Armenia and forced Tiridates II to flee. After the deaths of Tiridates II and his son Khosrov II, Shapur I installed his own son Hurmazd on the Armenian throne. When Shapur I died in 270, Hurmazd took the Persian throne and his brother Narseh ruled Armenia in his name. Under Diocletian, Rome installed Tiridates III as ruler of Armenia, and in 287 he was in possession of the western parts of Armenian territory. The Sassanids stirred some nobles to revolt when Narseh left to take the Persian throne in 293. Rome nevertheless defeated Narseh in 298, and Khosrov II's son Tiridates III regained control over Armenia with the support of Roman soldiers. Christianization As late as the later Parthian period, Armenia was predominantly Zoroastrian. However, this was soon to change. In 301, Saint Gregory the Illuminator converted king Tiridates III and members of his court to Christianity traditionally dated to 301 according to historian Mikayel Chamchian's "Patmutiun