Rome's most significant foe is the Parthian Empire.

Few countries were able to match the powerful Roman Empire in practically every aspect, let alone defeat it. One of these was the Parthian empire, the historic and cultural heir to the more well-known Achaemenid Persian empire that Alexander the Great overthrew.The Parthians are acknowledged as one of the hardest adversaries the Romans have ever fought, and with good reason. Roman legions were put to the test by Parthian warriors, who forced them to demonstrate their worth. But if the Parthian empire is only viewed as one of the "great enemies of Rome," it is easy to ignore other significant events in Parthian history.