The Roman Emperor conquers all of Parthia (Persia). It becomes a Roman province and is given priority by Trajan's successor Hadrian. Can the Romans actually hold it, given the long distance from the heart of the Roman empire and the hostility of the native population? Persia will become part of the Byzantine empire when the Roman empire divides. This means that the Byzantines will be in a much stronger position by the time that Islam comes on the scene. How does this change history?