The Parthian Empire and the Roman Empire had been rivals in the world for some time before the start of this War. The Parthians who inherited their Empire from the Persians lived in modern day Iran mainly but extended to OTl Iraq and as far as Afghanistan. The Roman Empire was led by the Emperor Marcus Aurelius who was asissted by the very powerful and famous General, Carolus. The Emperor Marcus Aurelius was not intent of pursuing war with these people but they began to act more hostilly against the Romans ever since the Emperor Vologases I of Parthia came to power. Vologases and the King of Armenia funded raids and other border attacks on the Romans which eventually culminated in a large, full-scale seige of the city of Damascus in Syria.