Background to the battle of Carrhae
The Parthian empire was perpetually menaced by hostile armies both in the east and in the west and was already deeply injured by the encroachments of Pompey. However, its decentralized and feudal structure may help to explain why it never mounted a strong offensive after the days of Emperor Mithradates II. Instead, Iran tended to remain on the defensive. The wars between Iran and Rome therefore were initiated not by the Iranians – but by Rome itself. Rome considered itself obliged to claim the inheritance of Alexander of Macedonia and, from the time of Pompey, continually attempted the subjection of the former Hellenistic countries as far as the Euphrates River. As part of the attempt to extend Roman control further eastward, Marcus Licinius Crassus, the Roman triumvir, took the offensive against Iran in 54 BCE. Such then were the protagonists in the decisive battle that was about to develop.
Before the Roman march towards Parthia began, Crassus had been advised by a Roman ally, Artavasdes, king of Armenia, to lead his forces through the mountains of that country, to shelter from the Iranian cavalry. However, Crassus ignored this advice, being anxious to include in his army the substantial Roman garrisons posted during the previous season in the towns of Mesopotamia. Then, after crossing the Euphrates at Zeugma, he also rejected the plan of his legate Cassius, that he should follow the course of the river to Babylon. Instead Crassus followed the guidance of an Arab chief, whose name is given by Plutarch as Ariamnes. This seems improbable, and other sources name the guide as Abcar or Abgar, and identify him as the chief of the city of Edessa. This guide, suspected by historians of collusion with Surena, led the Romans away from the river into the desert, and towards the main Iranian force.
The strength of the two armies
With regard to the size of the two armies, that of the Romans was reportedly greatly superior in numbers. According to the most reliable account, that of Plutarch, Crassus commanded "seven legions, [with] little less than four thousand horse, and as many light-armed soldiers". A quarter of the latter were Gaulish troops lent by Julius Caesar. Other commentators have given somewhat higher total estimates. At the minimum estimate, the army of Crassus would have numbered thirty-six thousand men.
The Iranian forces under Surena consisted, according to Plutarch, of a thousand fully armored lancers, the cataphracts, who formed the bodyguard of the General. Nine thousand horse-archers formed the main body of the troops, and a baggage-train of a thousand camels was available to bring up extra stocks of arrows. The entire force was mounted, and therefore highly mobile under the desert conditions. However, in numerical terms, the Roman force seemed sufficient for the task in hand.
Events showed, nevertheless, that in two critical respects the Romans had underestimated the Iranian forces. The power of the horse-archers’ arrows to penetrate the legionnaires armour had not been appreciated, perhaps because the Roman commanders were unaware that the compound bow which the Iranians employed was a more powerful weapon than the lighter bows found at that time in Rome. Additionally, the Romans had anticipated that the Iranian cavalry would quickly exhaust their stock of arrows; but the camel train of General Surena made it possible for him to bring up plentiful stocks of arrows as the quivers of his men were emptied.
Additionally, the Romans were also ill-adapted to the open terrain of the battlefield. The vast distances of the Mesopotamian plain, and the heat (for the battle took place in June) put the Roman infantry at a disadvantage. Moreover, the Roman means of retaliation against their adversaries were ineffective, since the range of the Roman javelin was obviously limited, and the Gaulish horsemen relied on for a counter-attack were provided only with short javelins, as well as being lacking in adequate defensive armour.
With all these miscalculations, even the squares of Roman legionnaires could not hold their own against the Iranians.
The battle
At first the Romans prepared to advance to the encounter in extended line. Then Crassus formed the legions into a square, and so advanced to the River Balissus (Balikh). Contrary to the opinion of his officers, he decided not to camp by the water, but hurried the troops across, and before long came in sight of the advance-guard of the Iranians. The strength of their main body was at first concealed. Then the thunder of the Parthian drums burst on the ears of the Romans. The mailed cavalry of Surena's bodyguard uncovered their armour, and the sun glittered on their steel helmets.
"When they had sufficiently terrified the Romans with their noise, they threw off the covering of their armour, and shone like lightning in their breastplates and helmets of polished Margianian steel, and with their horses covered with brass and steel trappings . .".
The first attack was a charge by the lancers of the bodyguard, led in person by the towering figure of General Surena. Then, seeing the steadiness of the Roman legionnaires, the Iranian horse-archers began their work. What followed was more like a massacre than a battle.
The Romans had tried to offset their lack of cavalry by using light infantry mixed with their Gaulish horsemen. But such makeshift tactics were of little avail against the finest cavalry in the world. The legionnaires were soon hard pressed and all but surrounded, so that Crassus was reduced to ordering his son, Publius, who commanded one of the wings, to attempt a diversionary charge with his forces.
Publius led thirteen hundred horse, five hundred archers, and eight cohorts of the infantry, the latter totalling some four thousand men, into the attack. At first the Iranians retired in front of them, but after Publius’ men were separated from the main Roman force they were quickly surrounded, offering an all but helpless mark to the rain of arrows. The threat of a charge by the Cataphracts forced the Romans into close order, thereby reducing their chances of escape. Though the Gauls caught hold of the Iranian lances to pull down the riders, and ran under the horses of their enemies to stab them in the belly, these were no more than tactics of desperation. Soon the young Publius was disabled, and the remnant of his force retired to a mound to make their last stand. The young and naïve commander ordered his Armour-bearer to end his life, although five hundred of his soldiers survived to be taken as slaves.
This agonizing diversion had temporarily relieved pressure on the main Roman force. But the magnitude of the disaster became clear when the Iranians rode back with Publius’ head on a spear. Thereafter the main Roman body had to defend themselves as best they could for the rest of the day under the constant hail of missiles. Only when it grew too dark to shoot did the Iranians draw off, leaving the Romans to pass a melancholy night, encumbered as they were with the many wounded, and anyway anticipating their final destruction on the following morning.
The Roman retreat
By this time, Crassus himself was prostrate with despair. Octavius and Cassius, his lieutenants, resolved that the only hope was to escape under cover of darkness and seek shelter behind the walls of the city of Carrhae. Thus they slipped away silently from the camp in the darkness. Those of the wounded who could be moved obstructed the march, and the majority, who had to be abandoned, raised the alarm with their cries. Understandably, retreating in the dark, the Romans fell into disorder. A party of three hundred horsemen did reach the city at midnight, and warned Coponius, commander of the garrison there, that Crassus had fought a great battle with the Iranians. They then turned west to make their escape across the Euphrates. Another detachment of two thousand men under the Roman officer Varguntius lost their way in the dark, and were found by the Iranian forces in the morning, marooned on a hill. Of these, only twenty made their escape. At Carrhae, Coponius suspected a mishap, and called his men to arms. Then he marched out, and led Crassus and the main body of the Romans into the city.
There were no supplies in Carrhae for a long siege, nor hope of relief from the outside, since Crassus had concentrated all the forces in the Roman East in his army. The Roman commander therefore determined to break out of the city on the second night, and make his way to safety in the shelter of the Armenian hills. Once again, his guide, Andromachus, was a Parthian sympathizer, who was rewarded after the Roman debacle with the governorship of Carrhae. It is said that Andromachus misled the main Roman column in the dark, so that by dawn they were over a mile from the shelter of the hills. Octavius had a reliable guide and took refuge in the mountains. At daybreak, Crassus and his force had occupied a spur connected by a low ridge to the main mountain range. When they came under attack, Octavius and his men moved down from the heights to offer support. At this moment Surena rode forward to offer terms of peace and to spare the Roman’s lives. It is not clear whether Crassus accepted voluntarily, or under pressure from his men, but he and Octavius, with a small group of Romans, went down to meet the Iranians. The latter mounted Crassus upon a horse, to take him away for the signing of the treaty. Octavius, suspecting foul play, seized the bridle of the horse, and, when a scuffle broke out, drew his sword. In the melee that followed, all the Romans in the party were slain and their leaderless troops then either surrendered or scattered. Very few were successful in making good their escape. Of the entire force, twenty thousand are said to have been killed; while ten thousand were captured and deported to distant Margiana as slave labourers. Thus ended the disastrous Roman campaign of Carrhae. The Euphrates was firmly established as the boundary between the two Empires.
Despite the crushing defeat of the Romans, the Iranians made no attempt to follow up their victory or to invade the Roman Empire. The Romans learnt to introduce cavalry into their army, just as nearly a thousand years earlier the Assyrians had learnt from the first Iranians arriving on the Plateau.
The Roman defeat won unquestioned recognition for Iran as a military power superior to Rome and the resurrection of Iran as a united nation.
