When History Rhymes: Some History On The Roman-Iranian Wars In Late Antiquity

Khusrau made a cardinal mistake when the Persians seized the Christian holy relics in Jerusalem. More than anything else, this spurred the Christian empire of Rome into response as nothing else would, and in 622 Heraclius went on the offensive. In particular, Heraclius unleashed a demon that has continued to haunt the world ever since: he formulated the concept of Holy War whereby killing could be justified as a religious act and those who perishing in doing this would ascend directly to heaven. Heraclius first safeguarded his rear from the Slav threat by using Byzantium’s greatest single weapon, money: he simply bought them off. Then, armed with religious zeal, these first Crusaders were able to penetrate deep into Iran in 622 where they plundered the Iranian holy city of Shiz, partly to seize back the holy relics, and partly to avenge the plunder of Jerusalem.

In 624-5 Heraclius moved the war to Transcaucasia once more: the Caucasus remained a strategic factor throughout. Accordingly, Khusrau sent his three best generals into Transcaucasia, including Shahin, the legendary besieger of Constantinople. Faced with such opponents, Heraclius wisely avoided open battle. In the meantime, Khusrau’s diplomatic intelligence had been as busy as his military, and as successful. The following year his agents formed an alliance with the Avars, Slavs and Bulgars of south-eastern Europe in a move to encircle Constantinople. Acting in concert, the Sasanian army, commanded this time by Shahrvaraz, advanced in 626 once more to the Bosphorus, laying siege to Constantinople from Chalcedon, while the Avars laid siege on the landward side. Indeed, according to one source, Shahrvaraz actually crossed the Bosphorus and surrounded Constantinople, laying siege from the west as well. For the first time since Xerxes, an army from Persia occupied a part of Europe. Constantinople’s massive defences, however, held.

Faced with encirclement, Heraclius used the same tactic himself, and in 626 opened negotiations with the Khazar Turks of the Caspian to outflank Iran in the east. Accordingly, a Khazar army commanded by their king advanced through the Caucasus passes and joined forces with Heraclius under the walls of Tbilisi, which was still held by the Persians. Betrothing his daughter Eudocia to the Kagan (the first but by no means the last time that Byzantine and Turkish royal families would be united by marriage), the combined force entered Iran in 627, leaving a smaller Turk force to continue the siege of Tbilisi.

Heraclius advanced to the historic battlefield of Nineveh in 627, whose capture by the Medes in 612 BC had first signalled the arrival of the Iranians upon the Near Eastern stage. This time the Iranians were defeated and a combination of both luck and secret intelligence work began to work in Heraclius’ favour. The Persian general Shahin had died of illness the previous year, removing one of Khusrau’s military geniuses from the wat. This left only Shahrvaraz, still besieging Constantinople. Heraclius’ agents, however, were able to show him a letter of Khusrau, which Roman agents had intercepted, ordering Shahrvaraz’ execution as a potential challenger to his throne. Accordingly, Shahrvaraz entered into secret negotiation with Heraclius and withdrew his forces from Constantinople—the Persians ‘evacuated Europe and returned to Asia’ according to John of Ephesus.

The following vear Khusrau I Parviz was murdered, possibly at the instigation of his son Kavadh acting in concert with Shahrvaraz. His successor, Kavadh II, sued for peace in 629. Heraclius was able to negotiate an evacuation of Egypt directly with Shahrvaraz (now connected by marriage ties: Shahrvaraz’ daughter married Heraclius’ son) and a withdrawal back to previous borders.

Peace, like countless previous ones, was established once again. Many regard the wars between Rome and Sasanian Persia between the third and seventh centuries as ‘endemic’, as both empires claimed universal rule hence leaving few options apart from war. Others regard it as just another chapter in a Manichean war between east and west that we have reviewed in the Introduction. Both views overlook the long periods of peace between the two powers when trade and cross-fertilisation of ideas—particularly religious—-went both ways: relations between any two powers are always complex and can never be described in simple terms. More important, both views obscure the real significance of this particular century-long war.

After a century of war the borders remained exactly as they had been at the outbreak: the war, it seemed, had changed nothing. At the same time it had changed everything. Ultimately, it was not a peace like the previous ones, for the war had awoken a new giant from an unexpected quarter. Throughout the war, monotheistic religion had not only become arms of the state of both superpowers, but for the first time was used as offensive weapons: militant Persian Zoroastrianism versus militant Roman Christianity. The period also saw militant Judaism in the hands of an Arab prince in Yemen with Dhu Nawas’ religious offensive against the Christians. Furthermore, both powers used Arab allies to fight each other in proxy wars: Persian Lakhmids versus Roman Ghassanids. This combination of militant monotheism with resurgant Arab power was to have profound implications, particularly when we realise that Heraclius’ proclamation of holy war has its exact counterpart in the Islamic concept of jihad, first traditionally articulated by Muhammad in the very same year—622—-when Heraclius formulated his.

The story of the conflicts between the Romans, the Parthians, and the Persians is one of ongoing adaptation and innovation. Both sides learned from the other, trying to shift the odds in their favour. Well-balanced, all-arms Roman forces proved very hard for the Parthians to deal with in later generations. Over time, the two sides became more and more alike, so that the difference between the armies of the sixth and seventh centuries was slight, coming in matters of detail rather than overall style of fighting.

Tactically, the advantage between the two sides ebbed and flowed with neither gaining a decisive edge for very long. Strategically, it was much the same, especially once the Sasanians proved themselves as adept as the Romans in siege-craft, after which both sides were capable of taking strongly fortified cities. In the main, conquered territory was readily consolidated. There is no sign of long-term resistance to Roman rule in Mesopotamia, just as cities taken by war or treaty by the Sasanians appear to have accepted this new reality–in some cases because new citizens were brought in. The rebellions against Trajan in 116 need not mean that, in time, areas such as Babylonia could not have become reconciled to Roman rule.

That the Romans never conquered these regions had little to do with tactical and strategic capability. It did have a lot to do with the sheer scale of the task. Conquering substantial parts of the Parthian-Sasanian empire would have required very large numbers of troops and a willingness to wage war and enforce occupation over a long period of time. Trajan tried but was too old, although it is harder to say whether he gave up on the idea because of failing health or whether giving up was the trigger for his rapid decline. No one else really tried, whether because calculation swiftly led to the conclusion that such a project was too expensive, too difficult, or simply impractical in the foreseeable future, or more likely because the prospective advantages did not match the risks and cost. Instead, there was limited war with limited obiectives, both sides seemingly understanding the rules and stepping back from pushing the other too far.

Many wars were fought, however limited they were in scale and obiectives, but even though they figure prominently in our sources, they were rarer than we might expect. The first century was a time of almost unbroken peace, with Nero’s war in Armenia the only major exception. This conflict was very much a limited war, interrupted by frequent negotiation, and with a minor exception restricted to Armenia itself. If the second century saw grander campaigns, with two conflicts started by the Romans and one by the Parthians, it still meant barely a decade of fighting compared to some ninety years of peace.

In the third century and some of the fourth century, warfare between the empires became a good deal more common, only to be very rare indeed in the fifth century, then frequent after that.

The overall pattern is of long periods of essentially peaceful coexistence, which sometimes broke down. Whether from coincidence, their own agenda, or the side effects of Rome’s lack of internal stability, the era of the Sasanians witnessed far more conflict than that of the Arsacids. Even so, until the time of Khusro II, the Sasanians sought glory, profit, and the preservation or improvement of their position along the frontiers with the Roman provinces. They did not actively seek any greater outcome than this.

This was about dominance rather than conquest, and dominance in turn has a lot to do with perception. Throughout these seven centuries, both empires felt it necessary to demonstrate their might, to feel that they were strong and have others believe it as well. This was important for Rome’s elite under the republic and then for the emperors, and it was equally important for the king of kings, but there was always more than one audience.

The first was the peoples living outside the empire or near its borders. These needed to be convinced that the empire was so strong that it was far better to be its friend than its enemy. Ideally, this made everyone compliant, discouraging the rival empire from seeking confrontation, and making allies and provincial populations eager to please. Impressing this audience meant possessing substantial military forces and appearing willing and able to use them, and sometimes having to wage war as proof.

A second group was the population of the empire, especially the elite who were more significant politically. A ruler needed to assure this audience that he was a great and strong leader and that they were all part of the greatest empire in the world. In the main, most of this audience was far away from any actual conflict, which made it easier for a regime to exaggerate any achievements and present a treaty that was reasonably fair, or even involved concessions, as an unambiguous triumph.

On the whole, the system worked for both empires, allowing most rulers a measure of security from internal threats and avoiding conflict with the other empire unless it seemed advantageous There was good deal of bluster and sabre-rattling in all periods, each side revelling in proclamations of its overwhelming supremacy, even in diplomatic exchanges. Both sides knew the rules, imposing limits on their response. Simultaneously, a Roman emperor and a king of kings could each assure their own subjects that they were strong, and that the other man and his empire were weak and feeble, without this requiring an attempt to prove the claim by going to war. This was yet another way in which the two sides became so alike.