Parthamaspates, the son of Osroes I, spent much of his life in Roman exile. He accompanied the Roman Emperor Trajan on his campaign to conquer Persia. Emperor Trajan originally planned to annex Persia as part of the Roman Empire, but decided to place Parthamaspates on the Persian throne as a Roman client-king , which he did on 116. Following Roman withdrawal from the area, Osroes easily defeated Parthamaspates and reclaimed the Persian throne.

After his defeat in Persia, Parthamaspates again fled to the Romans who then, as a consolation, granted him rule of Osroene, a small Roman client-state between Asia Minor and Syria.