He had started from Brundusium in spite of the bad season, had landed at Dyrrachium, not without the loss of several vessels; thence, following the direct military road which led from the coasts of the Adriatic to the Bosphorus,[722] he had proceeded by land into Galatia, and had entered into Mesopotamia, after crossing the Euphrates.[723]
The Parthians, taken by surprise, offered no resistance, and the rich and flourishing Greek colonies on the Euphrates and Tigris, who detested the Parthian yoke, received Crassus as a liberator. The town of Nicephorium (Rakkah), situated near Ichnæ, on the Balissus, opened its gates to him; Zenodotium alone stood a siege. Instead of taking advantage of the concurrence of circumstances, and advancing promptly upon the Tigris, carrying the considerable town of Seleucia, Ctesiphon,[724] the ordinary residence of the King of the Parthians, and even Babylon, he confined himself to plundering the province. Having left 7,000 infantry and 1,000 cavalry in garrison in a few fortresses, he returned to Syria to take his winter quarters. There, without occupying himself with the next campaign, he only thought of committing exactions and of pillaging the temples of Hierapolis and Jerusalem.
At the commencement of 701, Crassus took the field again with seven legions, nearly 4,000 cavalry, and the same number of light-armed infantry,[725] and re-entered Mesopotamia. He had for lieutenants his son Publius, celebrated for his courage, his elevated sentiments, and his conduct in Gaul; the brave Octavius, who afterwards perished rather than abandon his general; Vargunteius, Censorinus, and Petronius: for quæstor, C. Cassius Longinus, esteemed for his valour and prudence, and who was, ten years afterwards, one of the murderers of Cæsar. An Arab had become his auxiliary; it was the chief of the Osroenes, Bedouins of the desert, who had formerly served Pompey in his campaign against Mithridates; he was named Abgaros, or Abgar,[726] and had been bribed by the King of the Parthians to betray Crassus.
Artabazus, King of Armenia, visited the proconsul at the head of 6,000 cavalry, promising him 10,000 more, and 30,000 foot, if he consented to attack the Parthians through Armenia, where the mountainous character of the country rendered their numerous and formidable cavalry useless. Crassus rejected this proposal, alleging the necessity of proceeding into Mesopotamia to the garrisons he had left there in the preceding year. These, in fact, were already blockaded by the Parthians, and soldiers who had escaped brought information of the immense preparations Orodes was making to resist him. A second time, then, he crossed the Euphrates, not far from Biradjik, the place of the passage of Alexander the Great.[727] There he had his choice of two roads to reach Seleucia: either to descend the left bank of the Euphrates to the point where it approaches the Tigris,[728] or to cross the desert. The first, proposed by Cassius, although the longest, procured him the immense advantage of having his right wing constantly supported by the Euphrates, on which boats could have carried his provisions. The second offered, it is true, a shorter passage; but in following it, the army was exposed to want of water and provisions, and to more laborious marches. The perfidious counsels of Abgar led him to prefer the latter. “There was not,” said the Arab, “a moment to lose, to prevent the Parthians from carrying away their treasures, and placing them in safety among the Hyrcanians and Scythians.” Crassus possessed some of the qualities which make a good general; he had given proofs of it in the war of the allies, as well as in that against Spartacus, but his faculties were paralysed by his covetousness. Glory ought to be the only thought of the soldier.
During this time, Orodes, King of the Parthians, had divided his forces into two armies: one, of which he took the command in person, went to ravage Armenia, in order to prevent Artabazus from joining the Romans; the other was entrusted to the vizier Surena, a man of merit, to whom Orodes owed his crown. Without undervaluing his intelligence, we are unwilling to believe, with some writers, that Surena invented new military tactics to oppose those of the Romans, and that that was the reason why, renouncing the employment of infantry, he made use only of cavalry. If he placed all his confidence in that arm, it was because the Parthians, in conformity with the nature of their country, generally fought only on horseback, and among them, as Dio Cassius says, infantry was of no value.[729] Surena’s talent consisted in the employment of the craft so familiar to the Asiatics, in order to surround Crassus with snares and traitors, and to draw him into the plains, where the advantage was all on the side of cavalry.
The army of the Parthians was thus composed solely of cavalry, some barbed with iron, as well as their horses,[730] and armed with long and heavy lances; others furnished with powerful bows and arrows, which, while they carried much farther than those of the Romans, perforated defensive armour.
After quitting the town of Carrhæ, the Roman army advanced towards the south, across the desert. The sand and heat made the march painful, while the enemy remained always invisible. At length, when they arrived on the banks, of a small river, the Balissus (Belick), which flows into the Euphrates, they perceived a few Parthian horsemen. Abgar, sent against them with a vanguard to reconnoitre, did not return. The traitor had betrayed Crassus to Surena. The proconsul, impatient and uneasy, then crosses the Balissus with his whole army, and, without allowing it to repose, pushes forward his cavalry, and obliges the infantry to follow it.
A few soldiers soon arrive to inform Crassus that they are all who have been able to escape from an ambuscade into which his vanguard has fallen, and that the whole Parthian army is on its march to encounter him. At this intelligence, he, who believed that the enemy would not dare to wait him, becomes confused, and hastily forms his troops in array of battle on a long front, for fear of being surrounded. The cavalry is on the wings; the Osroenes form a last line. The Parthians first throw forward their light cavalry, which makes whirls in the plain, raising clouds of dust, and causing the air to ring with their savage cries and the noise of their drums,[731] and then retire as if in flight.[732] Crassus sends forward against them his light infantry; but, surrounded and overwhelmed with the more powerful missiles of the Parthians, it is obliged to take refuge behind the legions.
On a sudden, the Osroenes whom Abgar had not carried with him attack the Romans in the rear,[733] and at the same time appear, glittering in the sun, the long lines of the cuirassed horsemen. Crassus then forms his army in a square. Each face is composed of twelve cohorts, and the rest is in reserve. The cavalry and light infantry, divided into two corps, flank two opposite sides of the square.[734] Publius and Cassius command, one the right, the other the left. Crassus takes his place in the centre.[735] The heavy cavalry, lance in rest, charge the great Roman square, and attempt to break it; but the thick and close ranks of the legions oppose an invincible resistance. The Parthians fall back a certain distance and call up their numerous archers, then, all together, they return in line, and throw upon the deep masses of the Romans a shower of missiles of which none fail of their aim. The legionaries, if they remain in their position, have the disadvantage of their pila and slings, which carry but a short distance, and, if they advance to use their swords, they lose that cohesion which forms their strength. Without moving, and defending themselves with difficulty, they see their numbers diminish without being discouraged; they hope that the enemy will soon have exhausted his munitions. But the ranks of the Parthians succeed each other; as quickly as the first have used all their arrows, they go to fetch others near a long line of camels which carry their provisions. The combat has lasted several hours; and the Parthians continue to extend their circle, and threaten to surround entirely the great Roman square.
In this critical position, Crassus can only have recourse to his cavalry. The side hardest pressed by the enemy is that commanded by Publius; his father orders him to make a desperate effort to disengage the army.