The Sasanian overthrow of the Parthians coincided with the beginning of a long period of upheaval and instability in the Roman Empire, which is generally recognized as becoming even more pronounced following the death of Severus Alexander. The period has long been described in modern scholarship as a dire time for the whole empire, and contemporaries such as Dio and Herodian had already begun to portray it in this way.7 A notable feature of this instability was the regular turnover of the imperial leadership from the death of Severus Alexander until the beginning of the reign of Diocletian. Short imperial reigns during this period were often the result of civil wars, and the upheaval associated with them. The depleting effects of civil war together with contemporary complaints of poor military discipline, particularly in the eastern army, might at first have caused problems in meeting the Sasanian attacks on Roman Mesopotamia and Syria.8 The problem of poor military discipline, however, was not necessarily a new one and the eventual Roman response to the early Sasan-ian attacks on Mesopotamia was to mount large-scale offensives in a similar way to those that had been undertaken against the Parthians in the second century.9 The campaigns of Severus Alexander and Gordian III required significant resources and troops, and in the 250s, when the Persians invaded the Roman eastern provinces throughout most of the decade, the Romans mustered two large armies to meet them in the field. The crisis, as it has been identified at a number of levels, had not yet translated into an inability to place large numbers of troops in the East regularly but imperial resources were clearly under considerable pressure.
There is little doubt that the Roman Empire was more stretched in terms of military resources during the third century than in previous times. This impacted upon military leadership and the ability to supply better organized and disciplined troops for campaigns against the Persians. The extent to which Roman resources were under pressure was particularly evident when Rome faced Persian invasions in the East, coupled with invasions of Germanic tribes on the Rhine and Danube rivers in the West. The Roman army experienced some major defeats on the Rhine/Danube frontier, which included a battle against the Goths in 251 in which the emperor Decius was killed. Rome also lost large forces near Barbalissos in 252/253 and Edessa in 260 when the emperor Valerian and the Praetorian Prefect were among those taken into captivity. By 260, the Roman Empire clearly faced a major crisis in the East and was forced to rely on the Palmyrenes to regroup and lead what remained of its legions there. Following the death of Odenathus of Palmyra and the ensuing regency of Zenobia, large sections of the provinces of Syria, Mesopotamia, Egypt, Arabia and even parts of Asia Minor experienced periods in which Rome was not in military or political control.
The problem for Rome in its eastern provinces during the third century following the Sasanian overthrow of the Parthians was not only the effects of unstable imperial leadership and wars on two fronts but what also appears to have been a limited capacity to engage the Persians effectively due to the latter’s ability to advance quickly and employ sophisticated military techniques such as siege warfare. The Romans knew little of the events in Iran that had led to the Sasanian Persian victory and, consequently, the military effectiveness required of the Sasanian Persians to defeat the Parthians. While the previous establishment of the province of Mesopotamia had not been seriously challenged by the Parthians, the Sasa-nians sought to contest Rome’s power in the province. They also challenged Roman power in Armenia and an apparent Roman military presence at Hatra in the 230s. The Roman fortifications on the Euphrates and in Mesopotamia were not equipped to deal with the enormity of the invasions that took place in the 250s, and they struggled in the earlier attacks of the 230s and 240s. As the Parthians had never undertaken such significant military campaigns against the Romans, the fortifications were not designed to withstand such overwhelming attacks. On the middle Euphrates and lower Khabur in particular, fortifications were not designed to withstand significant attacks and were more directed at establishing Roman authority and control over the territory of which they were a part. Roman internal problems, which included poorly disciplined and organized troops in the East, poor knowledge and experience of Sasanian offensive military tactics, and a defensive system not designed to meet large-scale attacks, made an effective defence all but impossible. The Sasanian invasions were to have profound ramifications for the Romans in the Near East, most notably in territory on the middle Euphrates and at Palmyra.
World History
