[Verginius Rufus]

The Persians don't become a problem until the 220s--until then the enemy in the east was the Parthian kingdom. There was a major war against the Parthians in the 160s, commanded by Lucius Verus (co-emperor with Marcus Aurelius).

Marcus Aurelius spent much of his time on the Danube frontier fighting the Marcomanni and Quadi--he died either in Vindobona (modern Vienna) or at another place on the Danube. His successor Commodus quickly ended the war--sort of the Roman counterpart to Obama being eager to end Bush's war in Iraq regardless of the consequences.

[pierrem15]

Not sure I agree entirely-- the fact that the Parthians were not as great a threat as the Sassanids is undoubtedly true, but the fact that the threat was real enough to send Lucius Verus with a substantial army to the East (draining resources from the Danube frontier) shows that the fundamental strategic threat to the Empire was already serious at the time Marcus Aurelius.

The fact that both campaigns ended indecisively also did not bode well for the Romans. Only a little more than sixty years before Trajan was able to mop the floor with the Persians, and (with difficulty) to acquire Dacia.

In retrospect it appears Hadrian's decision to call off Trajan's Persian campaign and build enormous and costly frontier fortifications may have been a grave mistake.