Ancient History & Civilisation

The War

Chapter 4

An Unnecessary War? – The Origins of the First Romano-Parthian War (96–55 BC)

Before we examine the details of the campaign, we need to take stock and look at the origins of the war and see how this affects the way we view the campaign that followed. This is a necessary step as most ancient and modern sources portray this war as being nothing more than unwarranted Roman aggression, fuelled by Crassus’ greed, ambition or sense of military inferiority, all of which have been suggested at some time.124 The contention here is that this war was not simply dreamed up by Crassus against a state which had done nothing to warrant it, but an inevitable clash between the two rising superpowers of the ancient world. Thus we need to draw together the strands that we covered earlier (in chapters one and two), remove them from a purely Roman or Parthian perspective and combine them to provide a more rounded view of the whole process.

As we have seen, by the second century BC the great powers that had emerged from the ashes of Alexander the Great’s empire were in decline, with a new generation of states rising to prominence and challenging the established order. We must not make the mistake of looking at this process from a narrow European or Mediterranean perspective, as Rome was not the only rising new power. To view the ancient world in such a way limits our perspective and gives the rise of Rome a certain degree of inevitability. As well as Rome there was Pontus, Armenia and Parthia. The first century BC saw these new powers clash with each other in a round of wars that would determine which civilisation would emerge as leading power of the ancient world.

By the 50s BC there were only two candidates left in this field, Rome and Parthia. In a way it was fitting that it came down to these two powers, as they both represented opposing civilisations, both coming from the extremities of the so-called ‘civilised’ ancient world. If we analyse the events of the century preceding the outbreak of the First Romano-Parthian War, it can be seen that there are four distinct phases of contact between Rome and Parthia and that the war that broke out in the 50s BC was not due to the actions of any one man, but was the result of the wider forces of history.

Contact Avoided

It would be misleading to start the relationship between the two empires with the point that they first physically met. It is clear that for the first century of its existence the Parthian empire occupied only the fringes of the consciousness of the ancient world, a problem for the Seleucids and nothing more.125 That all changed in 141 BC when Mithradates I invaded and annexed Mesopotamia and took the Seleucid king (Demetrius II) hostage. Such an action would have made the ancient world stand up and take notice of this new power from the east, and none more so than the Romans. The Romans had come to see the Seleucid empire as within their sphere of influence, often interfering in her domestic affairs, so the rise of a new power threatening Seleucia must have raised some concerns in Rome.

There is a terrible tendency for the ancient and modern scholars of Rome to ignore Parthia until the first century BC. Yet by 141 BC, Parthia stood poised to invade Syria itself and either annex it outright or, more probably, install a puppet ruler (Demetrius II) on the throne. Such an action would have been seen as direct interference in Roman affairs and would have seen a new empire appear on the shores of the Mediterranean, an event which would have surely demanded Roman intervention. Such a worry can only have been inflamed by the defeat and death of Antiochus VII in 129 BC when, once again, Parthia stood poised for an invasion of Syria. As it happened, the question of whether Rome would have intervened or not became an academic one, as Parthia suffered a barbarian invasion from the east which would occupy her for a generation. Rome, too, as described earlier, suffered from a lapse of concentration with regards to the Near East, occupied with bloody political infighting at Rome, as well as wars in Africa and Northern Italy. For the next thirty years both empires neglected affairs in the Near East and were far more occupied in other parts of their empires or with affairs at home.

The intriguing aspect of this period is just how close the two great empires came to clashing and just how far back the roots of the clash between the two can be traced. Parthia does not appear to impinge on the Roman consciousness until the first century BC. This is the image that the surviving ancient sources appear to depict, a view echoed by their modern counterparts. There is often the impression that Parthia had reached its natural boundary of the Euphrates and that Syria was always a part of the Roman sphere of influence. Yet we have seen that Parthia had designs on Syria far before the Romans ever considered annexing it to their growing territories. In 129 BC, when a Parthian invasion looked imminent, the Romans had only just gained a territorial foothold in Asia Minor, never mind the Middle East. As it happened, events conspired to keep both empires away from clashing over Syria until seventy year later.

The main beneficiaries from the inattention of the two empires were the states of Pontus and Armenia. But, by the 90s BC, both had come to the attention of the great powers, who, having recovered from the various difficulties each had faced, once again turned their attention to the region. Parthia struck first, invading and defeating the Armenians. Although Armenia remained nominally independent, the heir to the throne, Tigranes, was taken as a hostage and Armenia became a vassal of Parthia. Upon the death of the old king, Parthian forces installed Tigranes as king of Armenia and received a handsome parcel of land for the Parthian Empire, only referred to as the ‘Seventy Valleys’.126

The relationship between Parthia and its vassal Armenia was a crucial one in this period as Tigranes allied himself, by marriage, to Mithridates VI of Pontus, which created a super-alliance of the two states that could dominate the Asia Minor region. Although the links are never clearly expressed in our surviving sources, lurking behind this alliance is Parthia, as the sponsor of Tigranes. The paucity of our sources will never allow us to unravel the tangled motivations here, but we can speculate about the role of Parthia in this alliance and what they were hoping for. Mithridates of Pontus was clearly pursuing an anti-Roman policy in the region and this alliance was bound to upset Rome. Perhaps Mithradates II of Parthia was playing a clever game by overseeing the creation of a regional alliance that would rival Rome and yet keep Parthian hands clean?

Whatever his intention, this Pontic-Armenian alliance did soon come to the attention of Rome. When Mithridates VI invaded and annexed Cappadocia, Rome’s focus returned to the east once again and they resumed the role of arbiter of international relations in the region, determining that a powerful kingdom of Pontus was clearly a strategic threat to Roman interests. The Senate demanded that Cappadocia be granted independence once more. Mithridates agreed to this, but no sooner had the Cappadocians elected a new king then the other wing of the alliance, Tigranes of Armenia, struck. The Armenians invaded Cappadocia, overthrew the new king and installed a puppet king who was loyal to Mithridates of Pontus.

It was at this point that Rome decided that they had to act, or allow the establishment of the new regional power of Pontus-Armenia on their borders. They too would have been well aware of the renewed Parthian threat, possibly sponsoring this alliance and using it as cover. Lucius Cornelius Sulla, one of Rome’s most promising generals was dispatched to free Cappadocia from outside rule and restore the overthrown king. Little detail remains of the campaign itself, but the Romans invaded Cappadocia and defeated a joint Cappadocian-Armenian army. The puppet king was removed and the old king restored. This marks the first occasion that Roman forces clashed with the Armenians. It is at this point that the first meeting between the representatives of Rome and Parthia took place and the background to this meeting should not be ignored, though it all too often is in the modern sources.

First Contact

In 92 BC the Roman pro-praetor, Lucius Cornelius Sulla, met with an emissary of the Parthian king, named Orobazus. Also present at the meeting was the newly-restored Cappadocian king. This historic meeting is little covered by our surviving sources, yet has proved fertile ground for modern misinterpretations.127 It appears that the Parthians initiated the meeting, ostensibly to offer friendship between the two empires, though it will be recalled that neither representative had any authority to negotiate a treaty. A lack of sources will never permit us to ascertain the Parthian intentions here, but the timing is perhaps indicative. Parthia’s vassal, Armenia, had just been defeated by the Romans and the meeting could have provided the chance for the Parthians to assess Rome’s intentions towards Armenia. It is also possible that they intervened, as the power behind the Pontine-Armenian alliance, to diplomatically shore up a situation that had been lost militarily. Certainly Rome took no further action against either Pontus or Armenia.

We have no clear record of what was discussed at the meeting, though we do know that Sulla physically placed himself between the king of Cappadocia and the Parthian emissary. This was a move designed to show Rome’s dominant position and a breach of protocol that amounted to a slap in the face to Parthia, which cost the Parthian emissary his life when the Parthian king found out about it. What is certain is that no treaty was agreed between the two powers, and certainly not one that bound the Parthians to keep to the east of the Euphrates. Not only is none recorded in the sources, but neither participant had the authority to conduct such an agreement. In any case, Mithradates II swiftly acted on his aggressive intentions towards Seleucid Syria.

It is unclear what message Mithradates II took from this meeting, with both sides offering friendship, yet warily eyeing each other up. Certainly the Pontic-Armenian alliance had been defeated in Cappadocia, but they were still a threat to Rome in Asia Minor. Not only was Rome entangled in this region, but in 91 BC a civil war broke out in Italy between Rome and her Italian allies. Uncoincidentally, it was in this period that Mithradates II moved on Seleucid Syria. In 88 BC, Parthian forces intervened in a civil war between the Seleucid king, Demetrius III, and his brother Philip, capturing the former and replacing him with the latter. The newly-crowned Philip II owed his throne to the Parthian king while his brother might be the perfect puppet if one were needed to be placed upon the Seleucid throne.

At this point it appeared that the Parthians were on the verge on overrunning the Middle East, with vassal kings on the thrones of Armenia and Seleucid Syria. This dominance was reinforced by the outbreak of the First Mithridatic War between Rome and Mithridates VI of Pontus, a nominal Parthian ally, but not one with a direct connection to Parthia. By the end of 88 BC, the Romans had lost Asia and Greece and had been pinned back to Italy, added to which was a further outbreak of civil war between Rome’s leading generals, with the city of Rome itself being attacked. It appeared that victory lay within Parthia’s grasp, which is usually the time that one is most vulnerable. And so it proved in this case, when the death of Mithradates II in 87 BC resulted in a complete collapse of Parthian power.

Thus the period of the 90s BC not only saw the first diplomatic contact between Rome and Parthia, but also saw a proxy war break out between the two, with Parthia backing the creation of a regional power block of Pontus and Armenia, which would keep the Romans occupied in Asia Minor, allowing Parthia the time and space to annex Syria. Once again however, the Roman and Parthian empires mirrored one another, when, within two years (88–87 BC), both collapsed into civil wars and both once again lost impetus in the region.

The disasters that befell Rome and Parthia proved to be a golden opportunity for Armenia. With Rome in the midst of a civil war, Parthia undergoing dynastic struggles (which may well have resulted in full scale civil war128) and Pontus recovering from the war with Rome (which ended with Mithridates’ defeat in Greece), Armenia was the sole regional power able to take advantage of the situation. Tigranes invaded both the Seleucid and Parthian empires, annexing Syria and taking a large swathe of Mesopotamia and Media from Parthia (see map 2). It is ironic that the first regional power to annex Syria was neither the Romans nor the Parthians, but the Armenians.

Collapse and Recovery

During the decades of the 80s and 70s BC the regional superpower was Armenia, but the basis of this position was the weakness of both Rome and Parthia, and it was the alliance with Mithridates VI of Pontus that was ultimately to lead to their downfall. Such an explicit alliance with a determined enemy of Rome was one that Parthia had avoided in this period. Parthia had neither the ability to intervene in the Mithridatic Wars, due to her own internal troubles, nor, it would appear, the intention. Even if Mithradates II had still been alive it is unlikely that the Parthians would have intervened directly. It was more likely that they would have strengthened their dominant position in the region, whilst keeping Rome busy fighting their agents.

Nevertheless, just as Armenia’s links to Pontus brought her to Rome’s attention, Parthia’s links to Armenia ultimately did the same. By 74 BC Rome had recovered from her civil wars sufficiently to engage with Mithridates VI of Pontus for the third and final time.129 Despite again starting the war slowly, the Romans, under Lucius Licinius Lucullus, soon defeated Mithridates and drove him from Pontus, as related previously. Mithridates turned to his allies for help. Tigranes of Armenia, by now the dominant regional power, stuck by his alliance and offered him refuge, whilst the new Parthian king, Sinatruces, refused to get involved, which was a good move given Parthia’s relative weakness in this period.130

Tigranes, however, had fatally miscalculated when he granted Mithridates sanctuary in Armenia, as the Romans were in no mood to compromise. Lucullus, operating well beyond his legal mandate, invaded Armenia in 69 BC and, in an act of desperation, both Mithridates and Tigranes appealed to the new Parthian king (Phraates III) for help against the Roman invaders. Tigranes even offered the restoration of the Parthian lands taken from them by Armenia as an inducement. Phraates was no fool however, and realised that Parthia was still in no shape to go to war with Rome and rightly gambled that he could regain those territories from a defeated Armenia. His assessment soon proved to be accurate as the Armenians were comprehensively defeated at the Battle of Tigranocerta, which perhaps created a false impression in the Roman minds about the fighting capacity of the armies of the region.

Following the battle, Lucullus turned his attention to the Parthians, sending them a clear warning not to get involved. According to the sources Phraates was negotiating with both sides, assuring them of his support for their cause, whilst determining to stay neutral131. Parthia was now negotiating with Rome from a position of weakness, a fact that both sides were aware of. Phraates’ price for supporting Rome was the restoration of the provinces of Gordyene and Adiabene in Mesopotamia from the Armenians.

It was at this point that Romano-Parthian relations took a decisive turn for the worse. Lucullus, tiring of the drawn out negotiations, sensing the weak position of Parthia vis-à-vis Rome and having defeated two of the three regional powers (Pontus and Armenia), apparently determined to attack Parthia.132 How seriously he intended this campaign to be prosecuted we will never know, as Lucullus suffered the twin blows of a mutiny of his troops and political manoeuvrings at Rome. Certainly it was a bold move, but Lucullus had too few men and had not yet finished off either Mithridates or Tigranes. Nevertheless it marked a clear change in the Roman line of thinking; a clash with Parthia now seemed inevitable.

As it happened, Lucullus’ position had been fatally undermined and, with no clear end in sight to the wars with Mithridates or Tigranes, his command was usurped by Pompey, who got the popular assembly to grant him an extraordinary command in the east. One of his first actions when he reached the east was to reopen negotiations with the Parthians. The sources disagree over the terms of this first formal treaty between Rome and Parthia. Either it secured Parthian neutrality or the arrangement was that the Parthians invade Armenia and open up a second front.133 Given the strength of Pompey’s forces, and the improbability of Pompey wanting to rely on foreign help, coupled with his later reaction to Parthian forces actually attacking Armenia, it seems unlikely that Parthian aid was required, merely their guarantee of neutrality. In any event, in 66 BC the Roman and Parthian empires forged their first treaty of alliance.

Perhaps emboldened by this, Phraates decided to take the offensive, rather than sit back. He supported the son of Tigranes in a bid against his father and Parthian forces invaded Armenia. No sooner had he invaded Armenia than his caution got the better of him and he withdrew, leaving the younger Tigranes to be defeated by his father. It was an ill-judged and tentative intervention and one that only served to further sour his relationship with Rome.

By 65 BC, both Mithridates and Tigranes had been defeated, leaving Rome, and Pompey in particular, as the dominant force in the Middle East. Now Romano-Parthian relations took another sharp downward turn. Whilst Pompey was in the Caspian region, his legate (deputy) Aulus Gabinius undertook a raid deep into Armenian territory, crossing the Euphrates and reaching the Tigris. Alarmed by such a deep Roman incursion into former Parthian territory, Phraates invaded the former Parthian province of Gordyene and seized control of it. He then sent ambassadors to Pompey demanding a final resolution of the previous year’s agreement, ensuring the return of the former Parthian territories from Armenia and the determination of the Euphrates as a line of demarcation between the two empires.134 It is likely that this last demand was more to limit the sphere of Roman activity than bar the Parthians from their traditional goal of securing Syria.

Pompey’s reply did nothing to assuage Parthian fears. He demanded the Parthian evacuation of the newly-seized province of Gordyene and on the matter of a line of demarcation, merely stated that ‘whatever border he determined would be a just one’.135 Upon encountering Parthian prevarication, Pompey ordered another of his legates, Lucius Afranius, to recover the province of Gordyene, by force if necessary. This was the first encounter between the forces of Rome and those of Parthia and appears to have ended with the Parthians withdrawing their forces rather than fight Rome.136 Afranius then pursued the Parthian forces back into the Parthian Empire, across the River Tigris and then returned to the Roman sphere of control by way of Mesopotamia during the winter of 65 BC, actually passing through Carrhae in 64 BC and finishing up in Syria.137

This tour by Afranius’ army was a clear sign of the impotence of the Parthians in the face of overwhelming Roman military superiority. If nothing else, it makes a mockery out of the claim that either Lucullus in 68 BC, or Pompey in 66 BC, had agreed to the Euphrates being the boundary between the two empires. There is no reason to believe that any Roman commander negotiated a clear border beyond which they could not pass. At the time Rome was militarily superior and Parthia visibly the weaker of the two and the whole concept would have gone against Roman notions of their imperial dignity.

By 64 BC, Pompey had still not decided to return the province of Gordyene to the Parthians. Phraates then engaged upon a dangerous gamble and once more invaded Armenia and waged war on Tigranes, who had been retained as king of Armenia by Pompey and who now was technically an ally of Rome. As the war dragged on into a stalemate, it is said that Pompey contemplated an invasion of Parthia.138 Unlike Lucullus, he now had a legitimate cause for a war and had the mandate and the forces. In the end he pulled away from such a confrontation, for reasons that have never been made clear, and brought all sides to negotiation. The fate of the former Parthian territories, held by Armenia, was to be decided by a three-man Roman commission, who decided that Gordyene was to remain Armenian (a key province in terms of access to Parthia) whilst Adiabene was to be returned to the Parthians.

Thus the Parthians regained part of their Mesopotamian territories, but were denied Gordyene by order of Rome. We will never know why Pompey pulled back from the brink of war with Parthia, caused by his own needling of them over the province of Gordyene. Certainly he would have given little regard for whether his mandate covered it, which it technically did, nor would he have cared much for what the Senate thought, as he had the popular assemblies on his side. Ultimately it would appear that he did not want to prolong his stay in the east with a potentially long campaign and it was clear (or so the Romans thought) that the Parthians were weak and did not require a war to deal with them. What Pompey did do, however, was to change his mind over the fate of Seleucid Syria and annexed the kingdom as a province of Rome. This about-face was probably due to his desire to keep Parthia in check and deny them access to the Mediterranean. In many ways Phraates’ desire for a Euphrates line of demarcation appears to have backfired on him, with the Romans annexing the territory west of the Euphrates.

Thus the period 74–64 BC saw a radical shift in the balance of power between Rome and Parthia. Up until this period, both Rome and Parthia had appeared to mirror each other in regards to the east. Both were successful when the other was, and then lost focus when the other did. In 87 BC Parthia appeared to have the upper hand, with client kings on the thrones of Armenia and Syria, and Rome having to fight off a Mithridatic invasion of Greece. The 80s BC saw both civilisations undergo massive internal strife and civil war, but, although the Roman civil war was far more devastating, they actually emerged from the period far stronger than Parthia. During Parthia’s weakness, Armenia had taken advantage and established herself as the dominant regional power.

By 64 BC Parthia had been reduced to bargaining with Rome for the return of her former territories and had been militarily humiliated by both Armenia and Rome. Both Lucullus and Pompey had contemplated war with Parthia, whose grip on her western territories was weak. By the time Pompey returned to Rome, Armenia was now a client state of Rome (with the strategic province of Gordyene as a hold over Parthia), Syria had been annexed and had two legions permanently stationed there. Annexing Syria took Roman territory up to the Euphrates and gave the two empires a common border for the first time (if you include both empires’ client kingdoms). This situation was the result of circumstance rather than treaty and it is highly unlikely that Rome had ever agreed not to cross the Euphrates. As Afranius’ campaign in 65/64 BC had shown, the Romans now had experience of operating in Mesopotamia.

In Roman eyes, and probably in reality, Parthia under Phraates III was weak. Parthian forces had refused battle in 65 BC and had been chased deep into Parthian territory, with Rome operating throughout Mesopotamia with impunity. The scene was clearly set for a future confrontation. Yet before Crassus entered the stage as the commander of a Parthian War, another man nearly got there before him.

The Phoney War

The years 62–57 BC marked a lull in Roman interest in the east. This was to be expected, given the defeat of Rome’s enemies and the lack of tangible threats in the region. Furthermore the focus of the Roman elite was on domestic politics, with the return of Pompey to Rome and the various activities relating to his return by his allies and enemies. In 58 BC, however, Aulus Gabinius, Pompey’s former legate (and one of the two commanders who had crossed the Euphrates in 65 BC), gained the consulship (with Pompey’s backing). His assigned province was originally Cilicia, but he managed to have it altered to that of Syria. The ostensible reason was to defend it against Arab raiders, who had always been a nuisance in that area. Nevertheless this did not warrant it being made a consular province, nor did it require a three year command and a substantial grant of legionaries and money (both unspecified by our surviving sources139). Clearly this indicated a substantial military campaign of some type and one backed by Pompey.

It is against this background that events in Parthia take a central role. In 58 or 57 BC (the sources are unclear on the specific year) the weak Parthian king, Phraates III, was murdered by his two sons (Mithradates and Orodes). Mithradates, being the elder, took the throne under the title of Mithradates III, but was then removed in a second coup by a group of nobles led by Surenas, who then installed Orodes as king. Mithradates was relegated to governor of Media, where he soon contacted the Romans to aid his restoration.140 Thus a second Parthian civil war was sparked off. At some point in 57 or 56 BC Gabinius agreed to side with Mithradates. By 55 BC a Roman army led by Gabinius crossed the Euphrates with the intention of putting Mithradates back on the Parthian throne as a client of Rome.141 Therefore the first war between Parthia and Rome looked set to begin, with Gabinius as the general in charge and the first Roman general to invade Parthia in an aggressive war.

Events in Rome intervened, however, when Pompey, Crassus and Caesar created their political alliance. As well as determining the consulships for 55 BC (for Pompey and Crassus) and another five year command for Caesar to complete the conquest of Gaul, the question of Parthia and Egypt came up, with the triumvirs apparently determining Roman foreign policy. It appears that during the conference at Luca, Pompey and Crassus agreed that the relatively easy job of invading Egypt and restoring Ptolemy XII to the throne of Egypt would be given to Gabinius, who already had an army in the east, whilst Crassus would undertake the proposed war with Parthia.142Thus Gabinius duly received a letter from his patron ordering him to turn back, withdraw from Parthia and invade Egypt instead, which he duly did. Entering Egypt in 55 BC, he restored Ptolemy XII to the throne, who then handsomely paid Gabinius and Pompey for their actions. Gabinius then turned to Judea and defeated an anti-Roman rebellion in the client kingdom there.


Through this brief analysis of Romano-Parthian relations, it can be seen that the war of 55 BC was not suddenly sprung on the Romans by a greedy and unscrupulous Crassus, as many sources would later claim. The war had probably been decided on in 58 BC by Pompey and Gabinius, the latter of whom had actually got as far as invading the Parthian empire before having to hand the command over to Crassus. Roman foreign policy in the east was now in the hands of the triumvirs and not the Senate. Pompey, and later the triumvirate as a whole, had come to the conclusion that the time was right to reduce Parthia to a client kingdom, as had been done with Armenia and Egypt. This decision was based on the experience of the previous decade, which had seen Parthia humiliated by Rome, with Parthian territory being decided upon by Roman commissioners, and the Parthian army allowing themselves to be chased out of their former territories rather than fight the Romans. If that were not enough then Parthia had just seen two successful coups against the reigning king and Rome now had a pliant candidate to place on the throne. In every way Parthia now resembled the other weak states of the region, ripe to be converted into a Roman client. It is against this background that we must consider the First Romano-Parthian War, as it alters our whole perspective on the campaign.

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