On the other hand the vizier met the Roman tactics, unsurpassed of their kind, with a system entirely different. His army consisted exclusively of cavalry; the line was formed of the heavy horsemen armed with long thrusting- lances, and protected, man and horse, by a coat of mail of metallic plates or a leathern doublet and by similar greaves; the mass of the troops consisted of mounted archers. As compared with these, the Romans were thoroughly inferior in the corresponding arms both as to number and excellence. Their infantry of the line, excellent as they were in close combat, whether at a short distance with the heavy javelin or in hand-to-hand combat with the sword, could not compel an army consisting merely of cavalry to come to an engagement with them; and they found, even when they did come to a hand-to-hand conflict, an equal if not superior adversary in the iron-clad hosts of lancers. As compared with an army like this Parthian one, the Roman army was at a disadvantage strategically, because the cavalry commanded the communications; and at a disadvantage tactically, because every weapon of close combat must succumb to that which is wielded from a distance, unless the struggle becomes an individual one, man against man. The concentrated position, on which the whole Roman method of war was based, increased the danger in presence of such an attack; the closer the ranks of the Roman column, the more irresistible certainly was its onset, but the less also could the missiles fail to hit their mark. Under ordinary circumstances, where towns have to be defended and difficulties of the ground have to be considered, such tactics operating merely with cavalry against infantry could never be completely carried out; but in the Mesopotamian desert, where the army, almost like a ship on the high seas, neither encountered an obstacle nor met with a basis for strategic dispositions during many days' march, this mode of warfare was irresistible for the very reason that circumstances allowed it to be developed there in all its purity and therefore in all its power. There everything combined to put the foreign infantry at a disadvantage against the native cavalry. Where the heavy-laden Roman foot-soldier dragged himself toilsomely through the sand or the steppe, and perished from hunger or still more from thirst amid the pathless route marked only by water-springs that were far apart and difficult to find, the Parthian horseman, accustomed from childhood to sit on his fleet steed or camel, nay almost to spend his life in the saddle, easily traversed the desert whose hardships he had long learned how to lighten or in case of need to endure. There no rain fell to mitigate the intolerable heat, and to slacken the bowstrings and leathern thongs of the enemy's archers and slingers; there amidst the deep sand at many places ordinary ditches and ramparts could hardly be formed for the camp. Imagination can scarcely conceive a situation in which all the military advantages were more on the one side, and all the disadvantages more thoroughly on the other.
To the question, under what circumstances this new style of tactics, the first national system that on its own proper ground showed itself superior to the Roman, arose among the Parthians, we unfortunately can only reply by conjectures. The lancers and mounted archers were of great antiquity in the east, and already formed the flower of the armies of Cyrus and Darius; but hitherto these arms had been employed only as secondary, and essentially to cover the thoroughly useless Oriental infantry. The Parthian armies also by no means differed in this respect from the other Oriental ones; armies are mentioned, five-sixths of which consisted of infantry. In the campaign of Crassus, on the other hand, the cavalry for the first time came forward independently, and this arm obtained quite a new application and quite a different value. The irresistible superiority of the Roman infantry in close combat seems to have led the adversaries of Rome in very different parts of the world independently of each other--at the same time and with similar success--to meet it with cavalry and distant weapons. What as completely successful with Cassivellaunus in Britain(6) and partially successful with Vercingetorix in Gaul(7)-- what was to a certain degree attempted even by Mithradates Eupator(8)-- the vizier of Orodes carried out only on a larger scale and more completely. And in doing so he had special advantages: for he found in the heavy cavalry the means of forming a line; the bow which was national in the east and was handled with masterly skill in the Persian provinces gave him an effective weapon for distant combat; and lastly the peculiarities of the country and the people enabled him freely to realize his brilliant idea. Here, where the Roman weapons of close combat and the Roman system of concentration yielded for the first time before the weapons of more distant warfare and the system of deploying, was initiated that military revolution which only reached its completion with the introduction of firearms.
Battle Near Carrhae
Under such circumstances the first battle between the Romans and Parthians was fought amidst the sandy desert thirty miles to the south of Carrhae (Harran) where there was a Roman garrison, and at a somewhat less distance to the north of Ichnae. The Roman archers were sent forward, but retired immediately before the enormous numerical superiority and the far greater elasticity and range of the Parthian bows. The legions, which, in spite of the advice of the more sagacious officers that they should be deployed as much as possible against the enemy, had been drawn up in a dense square of twelve cohorts on each side, were soon outflanked and overwhelmed with the formidable arrows, which under such circumstances hit their man even without special aim, and against which the soldiers had no means of retaliation. The hope that the enemy might expend his missiles vanished with a glance at the endless range of camels laden with arrows.