The Parthians had never posed a real threat to Rome’s control of Syria, nor had the Romans proved able to amass the resources and undertake the massive effort of conquering Parthia. Conflicts between the two powers had tended to focus on domination of the areas between their frontiers, especially the kingdom of Armenia. Trajan’s conquests in Mesopotamia had been abandoned by or soon after his death. At the end of the second century ad Severus created a permanent province of Mesopotamia, maintaining a permanent Roman presence east of the Euphrates. In 224 the last Arsacid king, Artabanus V, was defeated and deposed by a rebellion led by the Sassanid Ardashir. The Sassanid monarchy was stronger than its Parthian predecessor, but still faced the problem of controlling a disparate collection of royal lands, city states, sub-kingdoms and powerful noble families.
Palmyra was a desert kingdom which flourished within the Empire from its position astride the main trade route with the Orient. Here the triad of main Palmyran deities are shown wearing lamellar armour and with swords at their belts. In the chaos produced by Shapur I’s invasion, Palmyra became the leader of the eastern provinces in the effort to repel the invaders. After the death of its King Odenathus, who operated as a general of the Roman army, his widow Zenobia led a briefly successful attempt to create a new eastern empire based on Palmyra. Syria, and much of Egypt and Asia were overrun, and it teas not until the emperor Aurelian defeated the Palmyrans in 272 at Antioch and Emesa that the rebellion was suppressed. Zenobia was captured and led in Aurelian’s triumph, living out the remainder of her life in exile near Rome.
This silver drachma bears the head of Ardashir I (c. 209—42), the founder of the Sassanid dynasty. A subking of the Parthian monarch, he defeated and killed Artabanus V, the last Arsacid king, in 224. He later fought with Rome over and twice captured the border city of Hatra. The Sassanid Empire was to prove a more formidable opponent than the Parthian Empire it supplanted. Although its invasions still tended to take the form of massive raids, the Sassanids were to display far greater skill in siegecraft than their predecessors.
The Sassanid army was composed of royal troops and mercenaries, as well as feudal contingents supplied by the noblemen. Like the Parthians its main strength lay in its cavalry, the cataphracts and horse-archers. Although heavily armoured and equipped with lances for a massed charge, Sassanid cataphracts often displayed a preference for using their bows to deluge the enemy with arrows and wear him down gradually. The standard of individual training in horsemanship, archery and use of personal weapons was very high, but the level of training at unit level probably varied considerably. On several occasions the caution and good order of the Persian cavalry, especially in pursuing a beaten enemy or rallying quickly after a mounted charge, was noted by Roman sources. Persian armies tended to deploy in three distinct bodies, the centre and two wings, and often made use of reserve lines. Rarely would all three parts of the army attack simultaneously and often some sections would advance and then feign retreat to draw incautious pursuers on to the well-formed reserves. To their cavalry the Sassanids added Indian elephants carrying towers containing bowmen on their backs. Elephants intimidated the enemy by their size and frightened horses by their appearance and smell. Sometimes they created panic and disorder in the enemy ranks, making an opening which might be exploited, but they were vulnerable to missile fire, and of less use against steady troops. Numerous infantry accompanied the armies in the field, providing more archers and spearmen, but their quality was universally described as very low. Peasants impressed for service with the king, the infantry added to the spectacle created by the Persian army, but were not capable of standing up to good enemy infantry, and at best provided rallying points for the cavalry. One of the most significant differences between the Persian and Parthian armies was the far greater ability displayed by the former in siegecraft. Improved logistical organization allowed the Persians to supply a static force for the duration of a siege. Their armies also included the engineers required to construct and operate siege towers, rams and catapults, and displayed a willingness to accept the casualties inevitable in the storming of strong fortifications.
Rome’s eastern frontier
The long struggle between Rome and Sassanid Persia was focused around the control of the border fortresses, like Dara, Nisibis, Amida, and Dura Europus. Using these as bases each side raided the other’s territory, increasingly with allied soldiers recruited from the Arabian tribes. The loss of one of these fortresses was a major disaster for either side, greatly affecting the balance of power. On the occasions that the Romans launched a major expedition against Persia, it tended to follow much the same route down the Euphrates or Tigris as Trajan or Secerns had taken on their Parthian expeditions. A more serious threat to the stability of the Roman east came during the Palmyran rebellion of AD 262-73, when Queen Zenobia's armies overran Syria and much of Egypt and Asia Minor. This was finally suppressed by Aurelian who followed up his victories at Immae and Emesa with the siege and capture of Palmyra itself.
The synagogue at Dura Europus was richly decorated with murals showing Old Testament scenes. The figures are depicted in contemporary third-century costume, the Israelite warriors dressed as Roman soldiers. Scenes include the crossing of the Jordan and, on the far right of this picture the battle of Ebenezer (l Samuel 4). The warriors depicted wear iron scale armour, baved long, hexagonal shields decorated with horizontal bars, and carry swords. Probably from a desire to show the men s faces, none wear helmets, but a group next to the Ark of the Covenant have scale coifs covering their heads. Also shown are unarmoured and shieldless cavalrymen thrusting long lances underarm. Wall paintings from other buildings at Dura showed its garrison, Cohors XX Palmyrenorum, parading to witness a sacrifice.
The Sassanids claimed to be the successors to the Acheamanid Persia, the empire that had been overrun in a few years by the savage onslaught of Alexander the Great. As such their propaganda laid claim to all the old realms of the Persian Empire extending up to the coast of Asia Minor. They reinstated the dominance of the old religion of Persia, Zoroastrianism, the influence of which sometimes gave their wars a strongly religious quality. The Sassanids have often been perceived as a far more dangerous enemy to Rome than the Parthians had ever been. However, the Persians had as little success as the Parthians in maintaining a long-term presence west of the Euphrates in Cappadocia or Syria. The invasions which penetrated deep into the Roman East retained the character of large-scale raids. The Sassanid kings were rarely secure enough in their own realms to permit a concerted effort of conquest. Their main objective was to dominate the areas on the fringes of the two empires and in particular to drive back the Roman presence in Mesopotamia and Arabia. This could be achieved by direct attack on the Roman strongholds in this area, or by threats to Rome’s provinces or military victories which allowed the Persians to gain favourable treaties with Rome.
Ruins of the frontier city of Dura Europus, captured by Shapur I in about 252 and never reoccupied. Traces have been discovered of the final siege, including a tunnel dug by the Persians to undermine the city wall. The Romans dug a countermine to attack it, but the whole thing collapsed, trapping attackers and defenders alike.
The campaigns between Rome and Persia came to be dominated by the border fortresses, places like Nisibis, Amida and Dura Europos. Well fortified and garrisoned, they were difficult for either side to capture without large forces and considerable effort. As in the west, raiding became the most common activity for both sides. Both sides began to enlist the nomadic tribes of the area, the Saracetti, employing their mobility and predatory talents to raid the other’s territory. Only in major expeditions were battles between the two sides at all likely, and even then the Persian objective was often to mount a display of force to allow favourable negotiations. Large royal armies with their full complements of elephants and infantry moved in a rather stately fashion, presenting an image of great force, but lacking the flexibility of smaller, predominantly cavalry armies.
Siege of Amida The historian Ammianus Marcellinus was a staff officer with the garrison of Amida and left a vivid and detailed account of the siege and the city’s fall. By the fourth century the Roman army found itself more often as the defender than the attacker in siege operations and had developed the skills of defence to a high art. Yet in most respects the technology of siege warfare had changed little from the third century BC. To take a city by assault the attacker had to find a way over, through or under its fortifications. Each of these methods could he countered by measures taken by the defending garrison. Amida actually fell when a mound constructed by the Romans to lay artillery fire down on to the workers building the approaching Persian siege ramp collapsed and the spoil created a route directly into the city. The Persian willingness and ability to prosecute a siege and accept the high casualties likely in a direct assault made them a far more dangerous opponent than their Parthian predecessors. Nevertheless, most Persian sieges, notably the repeated attacks on Nisibis, ended in failure. In this period the advantage usually lay with the defenders.
Persian doctrine stressed that battles should only be risked when the army enjoyed great advantages of position and numbers.
Roman attacks on the Persians were more determined, and conformed to their traditional view of warfare as a life-and-death struggle. Julian amassed sixty-five thousand men for the two armies which comprised his invasion of Persia, probably the largest Roman force ever seen in the fourth century. A competently handled Roman force composed of reliable infantry and cavalry could usually defeat significantly larger Persian armies, but it proved difficult to gain much advantage from such successes. The Persians, like the Parthians before them, usually struck at the Romans’ lines of communication or raided into the eastern provinces to draw the invaders off. Julian inflicted several battlefield defeats on the Persians, but his most important successes came from the capture of forts and cities. Several Roman armies in the third and fourth centuries pressed on into Babylonia, sacking Ctesiphon, the old seat of the Arsacids, and still an important centre. Yet the total defeat of Persia was a massive undertaking, requiring huge resources of manpower and logistic support and involving long years of bitter campaigning. Julian’s expedition failed because he was unable to supply his vast army. As a result of this balance of power, conflict continued to consist principally of sporadic raiding from the border fortresses. Control of these allowed domination of the area and Ammianus was incensed when Julian’s successor Jovian, eager to extricate himself from the failed eastern enterprise, abandoned Nisibis, Singara and territories on the border.