Missiles fell on the capital city of Iraq. The invaders were speedy and destructive. Eventually they compelled surrender, and a Western army occupied much of the country.

The scene might be drawn from recent headlines, but it comes instead from the history of ancient Rome. When their empire stretched from Syria to Britain, only one power could challenge Roman arms on anything approaching an equal footing: the Persian rulers of the land that now comprises Iraq. This area, the location of numerous ancient civilizations, was the heart of a Persian empire that stretched from modern Pakistan to the Syrian border. The empire’s proud horsemen had ridden out from their ancestral Iranian homeland during the second century B.C. and established the capital city of Ctesiphon thirty-five miles from the site of modern Baghdad. During the following centuries, as they became great empires, Rome and Persia fought many wars. The Romans, for example, attacked Ctesiphon more than a half-dozen times, and on five occasions in the second and third centuries A.D. , they took the city by storm.

Roman victories in Iraq were transitory and self-defeating. Moreover, they were part of a conflict that lasted not for months or years or even for decades but for more than six centuries. The quarrel began during the late Roman Republic (133-27 B.C. ) and was handed down from the early Roman Empire (27 B.C. – A.D. 283) to the late Roman Empire ( A.D. 280-476) to the Eastern Roman, or Byzantine, Empire. Two dynasties, meanwhile, ruled the Persian Empire, the Parthians (238 B.C. – A.D. 227) and then the Sassanids ( A.D. 227-651), without any diminution in the conflict. On the contrary, the Sassanids were far more aggressive than their predecessors.

During the centuries-long struggle, border towns and provinces in the Near East passed back and forth like Alsace-Lorraine or the Polish Corridor would in nineteenth- and twentieth-century Europe. Unable to hold on to their gains, conquerors returned home and then had monuments to their victories carved in bold relief on the sides of cliffs. For the civilians whose lands the contending armies passed through, peace was fleeting–sieges, sackings, and deportations were common. Rarely in the history of human conflict has a feud such as the one between the empires of Rome and Persia lasted so long and accomplished so little. The Hundred Years’ War and even Rome’s long and epic struggle with Carthage were brief compared to Rome and Persia’s Near Eastern struggle.

Not surprisingly, the names of the Roman commanders involved in the conflict read like a roll call of the great commanders of ancient history. Julius Caesar’s planned invasion of Iran through Armenia was cut short by his assassination on the Ides of March in 44 B.C. Caesar had intended to avenge Marcus Licinius Crassus’ disastrous defeat by Persia near Carrhae (Harran) in 53 B.C. Mark Antony carried out Caesar’s invasion plan in 36 B.C. but without the great military leader’s tactical skill–he lost half his men in the mountains of northwest Iran and on the harsh winter march home through Armenia. Trajan wept when his armies reached the Persian Gulf in A.D. 115 because the great soldier and emperor was too old to continue on to India. Julian the Apostate was killed in an inglorious rear-guard action in A.D. 363 during a difficult retreat north after his army had failed to take Ctesiphon. And Justinian was forced to spend a fortune on border fortresses and bribes to protect his rear in Persia while his main armies were conquering Italy, North Africa, and Spain.

The names on the Persian side are far more obscure, but then Iranian history is little studied in the West, and the sources of evidence are not nearly as good as for the Romans. One has merely to glance at Iranian history, nevertheless, to see that the Persians too had their Caesars and Trajans. Shapur I ‘King of Kings,’ for example, plundered Antioch and captured Roman Emperor Valerian after crushing his army in A.D. 260, and Khusro II in 611 penetrated to the Bosporus, in sight of Constantinople, before a Byzantine counterattack drove him and his men back to Iraq. The blow and counterblow of Persian and Roman armies showed no sign of abating until both Rome and Persia were driven from the Fertile Crescent by a new power–the Arabs. The Sassanid state collapsed not long after the Arab victory at the Battle of Qadesiya in Iraq in 637. Byzantium survived but only after losing Syria, Egypt, Palestine, and northern Africa to the Arabs. The net result of the age-old Romano-Persian conflict was the Pax Arabica.

Any conflict that lasts for six centuries has a prima facie claim to inevitability. If the stakes had been small, then the two sides would not have let the conflict continue. Nor is it difficult to imagine causes for the war. When two armed empires face each other across a long border, sparks can fly, and Romans and Persians confronted each other across a long line running roughly from Armenia through eastern Asia Minor to modern northern Iraq and eastern Syria. Sparks indeed did fly, yet the rough balance of power between the two sides could have allowed an uneasy but peaceful coexistence between Rome and Persia. Indeed, Emperor Augustus, who ruled Rome from 31 B.C. to A.D. 14, negotiated just such a peace, which lasted more or less intact for a century until war again broke out during the reign of Trajan (98-117). Why, then, did the Roman and Persian empires pursue a six-centuries-long war against each other? Did substantive differences and aggressive ambitions feed the cycle of conflict?

To answer these questions, four stages of the long struggle need to be examined: the outbreak of war in the first century B.C. , culminating in Augustus’ compromise peace; the renewal of war following Roman aggression under Trajan in the second century A.D. ; the shift to aggression by Sassanid-ruled Persia and Rome’s response in the second and third centuries A.D. ; and, finally, the fruitless Byzantine-Persian wars of the sixth and seventh centuries A.D. A paucity of Persian sources and the prevailing Western orientation probably make it inevitable that the struggle is approached primarily from the Roman perspective.

By the first century B.C. , Romans and Persians, or Parthians, faced each other at the crossroads of the Near East. Commanded successively by Lucullus (74-66 B.C. ) and Pompey the Great (66-62 B.C. ), the Romans had fought their way into Armenia and had annexed central Anatolia (Asia Minor) as well as Syria. The Parthians of this era had consolidated their position in what is now northern Iraq and, along with Rome, intervened in the kaleidoscopic domestic politics of Armenia.

Both Armenia and northern Mesopotamia were of vital strategic interest. Ancient Armenia roughly comprised the same area as today’s Armenia plus the easternmost provinces of Turkey. Northern Mesopotamia was a triangular salient extending from the Euphrates River in the west to the modern Iran-Iraq border and the Tigris River beyond in the east; the northern edge of the salient extended into what is now Turkey.

Armenia is a country of rugged mountains, but it also offers an excellent east-west invasion route through the Araxes (Aras) River Valley. If the Romans controlled Armenia, they could take the Araxes route into Media Atropatene (modern Iranian Azarbayjan) and thence into the heart of the Iranian plateau. If, on the other hand, the Persians controlled Armenia, they could march westward into Rome’s Anatolian provinces of Cappadocia or Pontus. By denying the other side control of Armenia, each power could also greatly reduce the costs of defense. With a friendly client king in Armenia, for example, the Romans had no need to station large numbers of forces in Cappadocia and Pontus. Instead, they could defend those provinces from the large legionary base in Syria. If the Persians had an ally on the Armenian throne, they could likewise save money on the defense of Media Atropatene. The obvious solution, implemented by Augustus, was to make Armenia a neutral buffer state, open to the influence of both powers but to the armies of neither.

Northern Mesopotamia was another key strategic gateway, though of relatively little intrinsic value. Aside from a belt of cities, such as Edessa (Urfa), Carrhae (Harran), and Nisibis (Nusaybin), most of northern Mesopotamia consisted of more or less arid rolling steppes. To the west, however, was the province of Syria, one of the richest jewels in the Roman imperial crown, an agricultural breadbasket, and home to the great city of Antioch. With a population of perhaps half a million, Antioch was a city where caravan merchants from the East rubbed shoulders with the cream of the Greek intelligentsia and the backbone of the Roman military and governing class, as well as with the Syriac speakers of the countryside. Syria was also of great strategic importance, as it controlled the land route between Anatolia and Egypt.

Cross the Persian side of the border from northern Mesopotamia, however, and one entered a region of possibly even greater wealth. Here, one passed into Mesopotamia proper, the central Tigris-Euphrates Valley, an area of ancient cities and rich agriculture supported by vast irrigation projects. It was more sophisticated and richer than the Persian plateau. It is estimated, for example, that the Sassanid dynasty derived two-fifths of its wealth from Mesopotamia. As on the Roman side of the border, most of the population spoke Syriac. Not the least of the ironies of the Roman-Persian conflict is linguistic: Very few of the inhabitants of the lands over which the two sides fought spoke either Latin or Persian.

The prizes then, were clear. On the one side stood Roman Cappadocia, Pontus, and, above all, Syria; on the other was Persian Mesopotamia. The border regions of Armenia and northern Mesopotamia were the places where the two empires met.

Rome’s intervention in the Near East was the culmination of four centuries of conquest that transformed a tiny Italian city-state into a world empire. During those centuries, the Roman governing elite developed a distinct style of political and military behavior in the international arena. The dominant trait was a tendency toward preventive war against any potentially hostile power. Rome’s wars against Carthage, Macedonia, and the Gauls are examples of conflicts that conformed to this pattern. Coexistence did not come easily to Romans.

The Roman empire’s desire for glory pushed their armies eastward toward Persia. For centuries, every ambitious young Roman dreamed of winning a battle and returning home to celebrate a triumph. A triumph was not merely a victory parade, although the successful general–in a chariot pulled by white horses and with a laurel wreath on his head–would ride through the city of Rome to the cheers of the crowd, accompanied by his troops and with booty and captives on display. The ostentatious parade was an official recognition by the Roman Senate that the general had won a major victory and that, in effect, he was a man to be reckoned with. For many a Roman noble, the triumphal procession led to the Forum, where political success began.

In 55 B.C. , Marcus Licinius Crassus anticipated following precisely that road. The ambitious army commander envisioned leading Rome’s eastern legions to victory against Parthia. He would then have outdone Pompey the Great’s deeds in the East and matched Julius Caesar’s current victories in Gaul, both of whom were his rivals in Rome’s First Triumvirate. In addition to fear and glory, a third time-honored Roman motive for war underlay Crassus’ expedition–greed. Considered by many to be the richest man in Rome (Crassus once said that no one was wealthy unless he could raise a private army), Crassus understood this motive well. With the booty of Mesopotamia to tempt him, and with a glorious triumph in prospect, he could all but taste the political fruit that his war in the East would bear.

It did not turn out that way, though. Although Crassus is cited in some sources as planning an Alexander-style march on India, he probably intended the less grandiose objective of marching down the Euphrates Valley to capture Ctesiphon and the rich Greek city of Seleucia nearby. Victory would permit the expansion of Rome’s empire to include some or all of the land between the Tigris and Euphrates.

Alas, Crassus’ campaign was a clear violation of Pompey’s earlier treaty, which set the northwest boundary of the Parthian empire on the Wadi Balik, leaving the little kingdom of Osroene, between Parthia and Roman Syria, about sixty miles to the west, independent. Nor had Parthia done anything to provoke Roman intervention. But treaties counted for little against glory, fear, and greed. It could, moreover, be argued that since the Greek-speaking Seleucid monarchs had once controlled Mesopotamia, the area was a natural part of the Roman empire. In any case, Crassus expected an easy victory, since the Parthian army had performed tepidly when last observed by Rome in Armenia about a dozen years earlier. Crassus also had plenty of manpower: seven legions, a fighting force of about thirty thousand men, plus about ten thousand cavalry and light troops. Unfortunately, he failed as a tactician.

More than sixty years old, Crassus had relatively little war experience. After desultorily securing friendly towns in Osroene during his first year in the East (54 B.C. ), the next year he made the unforgivable error of underestimating his enemy by offering battle on flat plains tailor-made for Parthia’s cavalry.

The Parthian forces were led by a brilliant tactician known to us only as the Suren, that is, first lord of the nobility. Some argue that he was the hero of later Persian legend, Rustam. The Suren commanded about ten thousand cavalrymen, specialists in the rapid desert fighting by which the Parthians made their mark. Some were cataphracts, that is, mailed heavy cavalrymen armed with spears; others were light-armed bowmen able to fire in continuous volleys. These archers were masters of the famous Parthian shot, an arrow shot by a horseman who pivoted on his mount during retreat. Together, cataphracts and bowmen could deliver a devastating one-two punch: After the bowmen had forced the Romans into massing their ranks defensively, the cataphracts with their thrusting spears would charge. Rome’s response should have been to fight in the hills and to parry with a very large cavalry force.

The battle, fought about twenty miles south of Carrhae in June 53 B.C. , was a disaster, costing the Romans perhaps three-fourths of the nearly forty thousand men they had committed to the battle, including legionnaires, cavalrymen, and light-armed troops. Ten thousand men were captured and deported to central Asia. The eagles of seven Roman legions ended up in Parthian hands. Carrhae took its place, alongside Cannae (216 B.C. ), the Allia (ca. 390 B.C. ), the Caudine Forks (321 B.C. ), and Arausio (105 B.C. ), in the select pantheon of great Roman defeats.

Although he survived the battle, during the Roman retreat a few days later Crassus was captured and killed. His corpse was mutilated, and his head is supposed to have made its way to Seleucia, where it was presented to the Parthian king. So much for Crassus’ boast to a Parthian ambassador that he would dictate terms in Seleucia.

Vengeance now became a leitmotif of Roman policy, and not merely for psychological reasons, although the Battle of Carrhae and its aftermath made Parthia’s new status as a great power on a par with Rome all too clear. After Carrhae, Parthia moved its border westward to the Euphrates, opposite Roman Syria. Meanwhile, farther north, Armenia defected to the Parthian camp. The security of its empire required that Rome act. It is therefore small wonder that Mark Antony, who inherited Julius Caesar’s plan of invading Parthia through the ‘back door,’ via Armenia into Media Atropatene, undertook an eastern expedition in 36 B.C.

Antony’s greatest achievement in the East was diplomatic rather than military. By deftly negotiating a network of client states from Egypt to Armenia to share the burden of defending Rome’s eastern border, Antony unknowingly laid the foundation for a long-term diplomatic settlement. A brilliant general who was a seasoned veteran of foreign and domestic wars, Antony’s immediate goal, however, was victory on the battlefield. After recovering the legionary standards lost at Carrhae and the Roman prisoners who were still alive would come the re-establishment of Roman prestige in the East.

Antony supplied himself with sixteen legions for his eastern expedition, more than twice the size of Crassus’ force, as well as with cavalry and light-armed troops–a force of eighty thousand men. He was careful to march through mountainous territory, thereby denying the Parthian cavalry favorable terrain, and he secured Armenian help before entering Media. Unfortunately, Antony underestimated the enemy. He had barely arrived in Media when the Parthians attacked his siege train and the two legions defending it, leaving ten thousand Roman soldiers dead. Moreover, his Armenian ally deserted him.

Despite this setback, like his predecessor Crassus, Antony was undone mainly by faulty strategy. He concentrated on besieging cities, but the Parthian strength was their mobile army that lived off the land. Unable to capture Parthian cities because he had lost much of his siege equipment and unable to defeat their armies, Antony was forced to retreat from Media, harassed by the Parthians every step of the way. By the time he crossed back into Armenia, he had lost twenty thousand legionnaires, four thousand cavalrymen, and an undetermined number of light troops. Forced to leave Armenia in the dead of winter, Antony lost another eight thousand men during his retreat westward to Syria. Antony’s casualties rivaled Crassus’ at Carrhae. Rome was farther than ever from defeating Parthia.

Antony, meanwhile, turned his attention to civil war. His rival was Julius Caesar’s heir and great-nephew, Octavian (63 B.C. – A.D. 14). The two men’s fleets clashed at Actium in 31 B.C. , and Octavian emerged victorious; the defeated Antony committed suicide. Octavian became sole ruler of the Roman world and, renamed Augustus, was Rome’s first emperor. However grand his position, Augustus was a practical man with few illusions. He wisely recognized that if mighty Antony with sixteen legions had failed against Parthia on the battlefield, he, Augustus, was unlikely to do better. He decided, therefore, to solve Rome’s Parthian problem by using both diplomacy and force.

In 20 B.C. , Augustus took advantage of disorder in Armenia and Parthia to put on the throne of Armenia a new pro-Roman king, whom he backed up with an army. With this as a stick and a treaty as a carrot, Augustus struck a deal with Rome’s enemy. Although Persia had thrashed two huge Roman armies, it too had lost its taste for war, perhaps because victory had taken its toll of manpower and finances. In the north, Armenia would be a buffer state between the two great empires. In the south, Rome recognized the Euphrates boundary. Parthia, in turn, returned the legionary standards and all surviving Roman prisoners. Ever the master of public relations, Augustus declared victory without fighting a war. He even advertised victory on his coins with slogans like civibus et signis militaribus a Parthia recuperatis (‘citizens and military standards recovered from Parthia’).

In a sense, Augustus’ treaty with Parthia was a victory for Rome. The settlement would last more or less intact for a century. While there continued to be jockeying back and forth over Armenia, occasionally with the involvement of troops, the two sides remained at peace. By not avenging Carrhae on the field of honor, Augustus dealt Rome’s military reputation a setback, regardless of his attempt to disguise it as a victory. Yet Rome had finally achieved security in the East at little cost.

The relative tranquility came to an end, however, in A.D. 113, when Rome changed course, and Emperor Trajan mounted a massive invasion of Parthian territory. The Parthian king Osroes’ deposing a pro-Roman king in Armenia and installing a Parthian puppet had provoked the emperor. There had, however, been similar provocations in the past, which Rome had settled calmly with a small show of force. Trajan’s desire for glory was no doubt a factor, but there seems to have been method to his marching. During the last generation, Rome had slowly moved away from the client-kingdom system of border defense favored by Augustus. Under the new system, client kingdoms were annexed and made part of a network of forward defenses on favorable terrain, complete with walls, trenches, highways, and legions. In the Balkans, Trajan had already conquered the client kingdom of Dacia (Romania) and made it a Roman province. In the East, he planned to push the Parthians back east from the Euphrates and conquer northern Mesopotamia, whose hilly terrain was eminently defensible. He also annexed Armenia.

The Parthian state, meanwhile, had declined considerably and could no longer mount an effective opposition to Rome. With at least eleven legions and other auxiliary troops at his disposal, Trajan was victorious everywhere, conquering Armenia, cutting through what is now Iraq, capturing Ctesiphon, and finally reaching the Persian Gulf. Carrhae had finally been avenged but only temporarily.

Revolts broke out in 116, not only in newly conquered Iraq but throughout the empire. Trajan was forced to give up most of his Iraqi and Armenian conquests and to hurry westward. He died en route, a broken man. His successor Hadrian immediately abandoned the rest of Trajan’s eastern conquests, allowed Armenia to return to its client-kingdom status, and made peace with Parthia.

Trajan had stretched Rome’s resources dangerously thin; Hadrian made the necessary correction. Unfortunately, Hadrian’s realignment had dealt stability in the East a deathblow. Having shattered Parthia’s post-Carrhae mystique, Trajan opened the door to new Roman adventurism in Iraq. Romans now invaded the region frequently, capturing Ctesiphon again in 165 and 198. In 199, the Emperor Septimius Severus finally got a firm hold on northern Mesopotamia, where he established a permanent defensive boundary.

Wars, however, often leave unintended consequences. Rome lacked the power to annex northern Mespotamia, but Roman victories undercut the prestige of the Parthians, whose collapse was a Pyrrhic victory for Rome. The new Persian state that emerged under the Sassanid dynasty in 227 was a far greater threat than its predecessor. (Following the change of dynasty, the Parthians came to be called Persians.) Where the Parthians were loosely organized, the Sassanids were centralized; while the Parthians stood on the defensive, the Sassanids moved aggressively in hopes of restoring ancient Persian glory and driving Rome from the Near East; while the Parthian threat was sporadic, the Sassanids kept up the pressure; while the Parthians were poor at siegecraft, the Sassanids were skilled in the technology of siege warfare. The Sassanids styled themselves ‘Kings of Kings of Iran and non-Iran,’ a sign of their imperial ambitions. Rome had no choice but to respond to the threat that it had unwittingly created.

A prolonged Sassanid drive on Roman Syria took place during the third century A.D. , when King Shapur I (241-ca. 272) posed the greatest threat to Rome. Among the great king’s early achievements were driving the Romans from Armenia and extracting a humiliating ransom of half a million denarii from his foe. Antioch was attacked repeatedly and plundered in 260, the same year that Shapur crushed a Roman army at Edessa (Urfa) and captured the emperor Valerian, who died a Persian prisoner. A Persian Augustus, Shapur vigorously advertised this coup, most graphically on rock carvings near Shiraz showing the king on horseback and Valerian kneeling before him. Shapur deported hordes of Roman prisoners to Iraq and Iran; their permanent presence contributed greatly to the growing prosperity of these regions.

Rome, however, recovered, thanks to the heroic exertions of soldier-emperors like Gallienus and Diocletian, and ended the third century in a very strong position in the East. The Romans took Ctesiphon again in 283 and 298 under Emperors Carus and Galerius, respectively. More important, Galerius crushed a Sassanid army under King Narses at Ezerum (in Turkish Armenia) in 298. As a result of this decisive victory, Narses was forced to surrender northern Mesopotamia and five small provinces east of the Tigris. The Romans built up the city of Nisibis (Nusaybin) as a fortress guarding their new frontier.

The fourth century began with a respite for Rome in the East, thanks both to Galerius’ victory and to the construction of a new capital at Constantinople by Emperor Constantine the Great (312-337). This city symbolized Rome’s commitment to defense against the Sassanids–a good thing too, for by mid-century, under Shapur II (309-379), they were again pressuring Rome in northern Mesopotamia, and they captured several important border towns.

The empire was so hard-pressed by the German tribes in the West that it could ill afford a major, Trajan-style invasion of Iraq. Unfortunately, that is precisely what it got under Emperor Julian (361-363), a brilliant but headstrong man in his thirties who marched on Ctesiphon in 363. Julian not only failed to take the city but also made insufficient preparation for his army’s eventual retreat. Short of supplies and harassed by the enemy, Julian’s legions were stopped short when the emperor fell in a minor skirmish. Julian’s successor, Jovian, was forced to surrender Nisibis and everything that Galerius had won in 298 in order to gain a safe conduct back to Roman territory. The Sassanids held on to their new gains for 150 years as both Rome and Persia changed from ancient to medieval states.

Deprived of its western, Latin-speaking provinces by Germanic invaders, the Eastern Roman empire, centered on Constantinople, slowly evolved into the Greek-speaking Byzantine state. Meanwhile, in sixth-century Persia, society coalesced around the new and lasting medieval ideal of the courtier-gentleman. In spite of these changes, the Romano-Persian conflict continued. The decisive factors of instability, as they had been since the year 227, were Sassanid aggression and Roman overextension.

After a period of relatively peaceful coexistence for a century or so after Julian’s defeat, the conflict heated up again in the sixth century under the Sassanid Kavad (488-531) and particularly his son Khusro I (531-579). Khusro ‘the Just,’ as he was later known, was a great and ambitious administrative and military reformer. The aims of the Sassanids during sixty years of intermittent fighting (502-562) were generally less a matter of annexing Roman territory than of laying siege to major Roman centers (Antioch, for example, which fell in 540) and thereby winning plunder, prestige, and tribute from the Byzantine government. The Byzantines had no one but themselves to blame for this renewed threat.

Justinian (527-565) devoted most of his energy to reconquering Rome’s lost western territory in Italy, Spain, and northern Africa. In itself this was one of the spurs to Khusro’s war. Khusro feared the threat that a reunified Roman Empire might pose to Persia. Justinian’s efforts in the West forced him to strip the defenses of the East, an opportunity of which Khusro took advantage. In the end, the two sides made peace in 562, although the Byzantine Empire was required to make large annual subsidies to Persia. It was a hollow peace for Rome. Like Trajan, Justinian had overextended himself. His successors lost the reconquered western territories in short order, while Justinian’s settlement with Khusro was not backed up by the military resources it required–resources that had been devoted to the draining war in the West.

The last act–some might say that it was the most dramatic act of all–came forty years later. The protagonists were the Sassanid Khusro II ‘the Victorious’ (590-628) and the Byzantine Heraclius (610-641). In the face of a succession struggle in Byzantium, Khusro made a breathtaking sweep from Armenia through Anatolia and Syria down to Egypt. In effect, he had finally fulfilled the old Sassanid dream of a Mediterranean empire–only briefly though. Heraclius made a heroic reorganization of Byzantine defenses and counterattacked. The culmination was a great defeat of the Sassanid army on the plains of northern Iraq in 627. Khusro II was murdered a year later.

The epilogue is well-known. At the time of Khusro II’s death in 628, Mohammed was about to return in triumph to Mecca. He and his Arab armies were the real victors of the exhausting Perso-Byzantine wars. By the end of the century, they had conquered most of the Byzantine empire and virtually all of the Sassanid. Most of this territory has remained Muslim, if not Arab, until the present day.

From Crassus to Augustus to Trajan to Shapur I and Galerius, to Julian to Khusro I and Justinian, and to Khusro II and Heraclius–what are the lessons of the seemingly all-but-endless war between Rome and Persia?

The first, perhaps, is a simple deduction concerning imperial aggression: Empires often seek security, but sometimes they just simply seek. The Parthians had done nothing to justify Crassus’ invasion. The Sassanids, for their part, seem to have been less interested in avenging Roman invasions of Iraq than in acquiring a larger empire for themselves.

On the other hand, once the Rome-Persia conflict was engaged, it had a momentum of its own. More than one scholar has come away with the sense that Romans and Persians continued to fight each other for centuries because neither one could find another opponent worthy of their mettle. Neither Rome nor Persia had another great empire on its immediate border. Romans might fight in Germany, Persians might fight in Central Asia, but for each side, the Romano-Persian duel was the main event.

A third point is the paradox of parity. The two powers’ relative equality ensured that the conflict would go on and on. As soon as one side got the advantage, it tended to press it too far, like Trajan or Khusro II, and thus allowed the enemy to recoup. There was a constant cycle of conquest, overextension, and forced retrenchment.

Augustus had demonstrated that Rome’s security dilemma in the East was soluble through negotiation. The Parthians seemed quite willing to accept his point. Over time, nevertheless, it came back to war, as the forces of greed and glory reasserted themselves. First Trajan and then the Sassanids gave in to the temptation of the battlefield. Ironically, for all the centuries of conflict, very little land changed hands. Rome, the civilizer of Europe, barely touched what is modern Iraq. Persia left little mark on Syria or Anatolia.

Finally, of course, is an example of the irony of war if ever there was one: The Arabs inherited the energy that the two powers wasted on the conflict. In the long run, for both Rome and Persia, victory proved to be little more than a mirage.

This article was written by Barry S. Strauss and originally published in the Autumn 1999 edition of MHQ. For more great articles, subscribe to MHQ: The Quarterly Journal of Military History today!