Parthian Military Tactics and the Parthian Shot
What did a Parthian horse archer actually do in battle?
Strip away the literature and the answer is plain. He rode. He carried a composite bow of about 80 cm in length, horn-and-sinew laminated on a wooden core, with a draw weight in the 50–70 kg range — too heavy for an untrained archer, light enough for a steppe-trained one. He wore a soft cap or a bronze helmet, a quilted or scaled torso defence on a good day, and a small wicker or hide shield. He carried a sword or a long dagger for the moments when his arrows ran out or the enemy closed. He had at least one remount, often two, for the simple reason that an exhausted horse cannot be controlled at the gallop and cannot be made to gallop.
The composite bow was the weapon. Without it, the whole Parthian system is incoherent: a steppe cavalryman without a steppe weapon is just a heavy horseman, and heavy horsemen are expensive. The bow had a range of perhaps 200–300 m for useful volley fire, a much shorter range for the kind of aimed shot that would penetrate scale armour, and a rate of fire of perhaps ten to fifteen arrows per minute in skilled hands. The figures are modern reconstructions, based on experimental archaeology with reconstructed bows and on what the ancient sources say (the most useful source is Arrian’s Tactica and Ars Tactica, both of which discuss steppe archery with some care). No surviving Parthian bow tells us its draw weight directly, but the physical evidence of the arrowheads — many of them three-bladed, of the type modern archers call “bodkin-points” — is enough to confirm that the weapon was the steppe bow and not a Mediterranean self-bow.
The feigned retreat, properly understood
A Parthian feigned retreat was not a single trick. It was a coordinated, multi-unit operation that the Roman army of the late Republic never quite worked out how to counter, and that the Roman army of the early Empire eventually learned to counter by refusing to chase. The horse archers would pretend to flee, drawing the enemy out of formation; the enemy, in pursuit, would be funnelled into a killing ground — rough ground, a prepared position, or simply a place where the cataphracts had been held out of sight. At the right moment, the cataphracts would charge and the horse archers would wheel. The Roman army at Carrhae, formed up in a defensive square to resist the arrows, was, when the cataphracts appeared, vulnerable to a charge it had not seen coming.
The vulnerability of the system is worth naming. The feigned retreat required a properly coordinated second line; the cataphract charge had to land at the right moment; and the horse archers had to stay in range without being ridden down by heavier cavalry. The Roman emperor Trajan, in the campaign of 115–117 CE, was able to pin and defeat Parthian horse-archer units by refusing to be drawn into a pursuit; the Roman army of Lucius Verus, in 165–166 CE, did much the same in Mesopotamia. The Parthian tactical system was at its best against an enemy willing to chase. It was a system that worked on the psychology of pursuit, and a Roman army that had learned to stand was a different problem.
Cataphracts
The cataphract was the second pillar of the Parthian army. The rider wore a helmet, a coat of scale or mail, and thick leg defences; the horse carried a matching caparison. The weapons were a long lance — the kontos, a heavy thrusting spear two to three metres long, wielded couched under the arm rather than over the shoulder — a sword, and a mace. The cataphract’s primary tactic was the shock charge, at the gallop, into a formation of infantry or lighter cavalry. A line of cataphracts at the trot, with the kontos couched, presented a wall of points; at the gallop, the impact was on the order of a modern light-armoured car hitting a body of men.
The cataphract was slow to produce. The armour, the training, and the horse were all expensive, and a cataphract unit was a serious capital investment — the rough equivalent in pre-modern terms of a modern tank battalion. The Parthian solution was to hold the cataphracts as a strategic reserve, committed at the decisive moment, while the horse archers wore down the enemy. The combination of mobile missile fire and shock action was the heart of the Parthian tactical system. It was not, in fact, a Parthian invention; the type appears in the Greek East in the Hellenistic period and was adopted by Iranian and Central Asian peoples in turn. The Parthians refined the combination and used it more effectively than any of their predecessors or contemporaries.
The cataphract corps was largely a nobles’ army. The seven great Parthian houses — the Suren, the Karen, the Ispahbudhan, the Aspahapet, the Spandiyadh, the Sihbuya, and the Zhinvat — each maintained cataphract units, effectively private armies, that the king of kings had to negotiate with as well as command. The dependence of the Parthian state on the great noble families was both a source of its military strength and a structural weakness. A king who fell out with the Suren, as Orodes II did not long after Carrhae, could find his army refusing to fight. Surena was executed within a year of his victory over Crassus, on a charge that may have been trumped up. The same dependence would be the lever the Sasanians used to overthrow the dynasty in 224 CE.
The wider army
The standing royal army was a relatively small component of the larger Parthian war effort. The Arab client kingdoms of the Fertile Crescent — Osroene, Adiabene, Characene, Hatra — provided substantial numbers of light cavalry, camel-mounted archers, and infantry. The Armenian kingdom, ruled by a junior branch of the Arsacid house, was a major source of heavy cavalry and a useful buffer against Rome. The Caucasian peoples — Iberians, Albanians, Colchians — supplied infantry and light horse. The Greek cities of Mesopotamia (until they were sacked or absorbed) provided garrison troops and craftsmen.
Infantry was never the Parthian strong suit. The Parthian army fielded substantial numbers of foot soldiers — archers, slingers, spearmen, garrison troops — drawn from the free peasantry of Iran, from the Greek cities, and from the subject peoples of the empire. By Roman standards this infantry was poorly trained and poorly equipped, and it did not win set-piece battles. It did hold fortified positions, guard camps and baggage trains, garrison cities, and provide missile support. The Sasanians, who inherited the Parthian system, would correct this imbalance by building a serious infantry arm of their own. This was one of the reasons they were ultimately more dangerous than the Parthians to Rome.
Intelligence and the political dimension
A point that does not always get the attention it deserves. The Parthian state was an information power. The great noble families maintained networks of agents in the Roman world. The Armenian kingdom was a listening post. The Lakhmid and Ghassanid Arab client kingdoms on the Syrian desert — the Lakhmids in particular, who had their capital at al-Hirah on the Euphrates — were early-warning systems of considerable sophistication. The Parthian kings were often better informed about Roman political alignments than the Romans were about Parthian ones, and the support the Parthians gave at various times to Crassus, to Brutus and Cassius, and to the various Roman dynasts of the late Republic and the early Empire was based on real knowledge.
The Parthian intelligence system was the model for the Sasanian one, which was more famous and (probably) more thorough. The Sasanian documents from the Persian Gulf and the Syriac and Greek sources give us more detail for the fourth to sixth centuries than we have for the Parthian period, but the institutional continuity is clear. The Parthian intelligence system was also, in my view, a major reason why the Parthian state survived for as long as it did: a system that knew what was coming could absorb shocks that would have destroyed a less well-informed one.
Logistics and the horse-breeding regions
The Parthian logistical establishment was less developed than the Roman, but it was adequate to the scale of Arsacid operations. A horse archer required one to two mounts for sustained operations; the larger Parthian armies of the first century CE required tens of thousands of remounts. The Parthian state maintained royal studs in the great horse-breeding regions: Media (the Nisaean horse of the Achaemenid period was the most famous), Hyrcania, Armenia. The system was less developed than the Roman logistical establishment, but it was adequate to the scale of Arsacid operations, and the Arsacid kings had, in any case, less of a tendency to project force at great distances from their bases than the Roman emperors did. A Parthian army usually fought on or near the Iranian plateau; a Roman army often fought in terrain that was months of march from its supply depots.
What the Romans learned
The Parthian wars forced the Roman army to change. The legion, the basic Roman heavy-infantry unit, remained the centre of Roman military power, but the Roman army of the second and third centuries increasingly incorporated the lessons of the eastern wars: more cavalry, more mounted archers, more flexibility in tactical deployment. The cataphract, the four-horned saddle, and the composite bow would become standard equipment of the late Roman and Byzantine army, and the Sasanian field engineering of late antiquity — mining, siege towers, the organised field camp — would be a major influence on Byzantine practice.
The single most concrete example is the saddle. The Parthian and Sasanian saddle had four horns — two in front of the rider’s knees, two behind — that locked the rider in place and allowed him to fight effectively from horseback, including at the gallop. The Roman army adopted the four-horned saddle by the third century CE, and the four-horned saddle remained standard Byzantine equipment for another thousand years. The bit, the stirrup (the Parthian evidence for stirrups is thin but not absent), the composite bow, the cataphract, and the field camp all moved in the same direction. The Parthian wars were, on this showing, the slow education of the Roman army by the Iranian one, and the long process of adaptation was a development of the first importance in the military history of the late ancient world.
Sources
The principal modern accounts are A. D. H. Bivar’s chapter on cavalry equipment and tactics in the Cambridge History of Iran, vol. III (1983), and the more recent survey by Kaveh Farrokh, Shadows in the Desert: Ancient Persia at War (2007), which is a useful synthesis for the general reader. For the Roman response, the relevant sections of Brian Campbell’s The Army and Society in the Later Roman World (2018) and the relevant chapters of A. D. Lee’s War in Late Antiquity (2007) are the working references. For the Sasanian succession, see Klaus Schippmann’s entry on the Sasanian army in the Encyclopaedia Iranica (1986), which is the most thorough modern account.