Rome's Gothic Wars_ From the Third Century to Alaric - Michael Kulikowski [13]
The regular experience of warfare, in turn, fed into the pre-existent rhetoric of imperial victory and invincibility which provided part of the justification for imperial rule: the emperor ruled – and had the right to rule – because he was invincible and always victorious in defending Rome from its enemies. Thus even after imperial expansion stopped early in the second century, the need for Roman armies to win victories over barbarians was ongoing. The result was a constant stream of border wars, which allowed emperors to take victory titles and be seen to fulfill their most important task – defending the Roman empire from barbarians and from the eastern empire of Parthia, the only state to which Roman emperors might reluctantly concede a degree of equality. As we shall see in a moment, the militarization of the northern frontier had for many years had a profound effect on the barbarian societies beyond the Rhine and Danube, but at the start of the third century, a more acute transformation took place on the eastern frontier, again as a result of Roman military intervention.
From Parthians to Persians on the Eastern Frontier
Caracalla is the pivotal figure here as well. In 216 he invaded the Parthian empire, the creation of the central Asian dynasty that had displaced the Hellenistic Seleucids as the rulers of Iran and Mesopotamia during the last centuries B.C. Since the defeat of the Republican general Crassus at Carrhae in 53 B.C., Parthia had possessed an iconic quality as the mortal enemy of Rome that was not matched by the actual strength or competence of the Parthian monarchy. A Parthian war might be a significant ideological goal for a Roman emperor – it avenged Crassus, imitated Augustus, and followed in the heroic footsteps of Alexander the Great – but victories in Parthia could actually be quite easy to win. The Parthian empire was fractious, and its kings faced almost continuous revolts in their far-flung eastern provinces. Thus when Caracalla determined to luxuriate in the easy triumph of a Parthian victory, he unwittingly destroyed the Parthian monarchy. It was replaced by a much more dangerous foe, a new Persian dynasty known as the Sassanians. A Persian nobleman, Ardashir (r. c. 224–241), revolted against the overlordship of the crippled Parthian dynasty and by the middle of the 220s had defeated the last Parthian king.
Under Ardashir’s son Shapur Ⅰ (r. 240–272), the Sassanian monarchy not only imposed itself upon the old Parthian nobility and the subject peoples of the Parthian empire, but also undertook repeated assaults on the Roman empire – Greek and Roman authors attributed to him the ambition of restoring the ancient Persian empire of the Achaemenid dynasty, which had been conquered by Alexander the Great 600 years earlier. Caracalla was murdered in 217 while still on his Parthian campaign, but the new Sassanian Persia became the chief focus of his imperial successors. Not only was there the continued lure of a prestigious Persian victory, there were sound strategic reasons for the imperial focus on the East: Persian raids on the eastern provinces – unlike barbarian attacks on other frontiers – threatened the permanent annexation and removal of the provinces from imperial control. Yet the relentless draw of Persia might distract imperial attention from problems on other fronts, and failure against Persia could be fatal to an emperor’s hold on his throne – the