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.