The Roman soldiers, when they heard of the numbers of the Parthians and their mode of fighting, were dispirited; the soothsayers announced evil signs in the victims; C. Cassius Longinus, the quæstor, and his other officers, advised Crassus to pause, but in vain. To as little effect did the Armenian prince Artavasdes, who came with six thousand horse, and promised many more, counsel him to march through Armenia, which was a hilly country, and adverse to cavalry, in which the Parthian strength lay: he replied that he would go through Mesopotamia, where he had left many brave Romans in garrison. The Armenian then retired, and Crassus passed the river at Zeugma (53); thunder roared, lightning flashed and other ominous signs, it is said, appeared; but they did not stop him. He marched along its left bank, his army consisting of seven legions, with nearly one thousand horse, and an equal number of light troops.
As no enemy appeared, Cassius advised to keep along the river till they should reach the nearest point to Seleucia; but an Arab emir named Abgarus, who had been on friendly terms with the Romans when Pompey was there, now came and joined Crassus, and assuring him that the Parthians were collecting their most valuable property with the intention of flying to Hyrcania and Scythia, urged him to push on without delay. But all he said was false; he was come to lead the Romans to their ruin: the Parthian king Orodes had himself invaded Armenia, and his general Surenas[109] was at hand with a large army. Crassus, however, giving credit to the Arab, left the river and entered on the extensive plain of Mesopotamia. Cassius gave over his remonstrances; the Arab led them on, and when he had brought them to the place arranged with the Parthians, he rode off, assuring Crassus that it was for his advantage. That very day a party of horse, sent to reconnoitre, fell in with the enemy, and were nearly all killed. This intelligence perplexed Crassus, but he resolved to proceed; he drew up his infantry in a square, with the horse on the flanks, and moved on. They reached a stream, where his officers wished him to halt for the night, and try to gain further intelligence; but he would go on, and at length they came in sight of the enemy. Surenas however kept the greater part of his troops out of view, and those who appeared had their armour covered to deceive the Romans. At a signal the Parthians began to beat their numerous kettledrums; and when they thought this unusual sound had thrilled the hearts of the Romans, they flung off their coverings and appeared glittering in helms and corslets of steel, and pouring round the solid mass of the Romans, showered their arrows on them, numerous camels being at hand laden with arrows to give them fresh supplies of their missiles. The light troops vainly essayed to drive them off; Crassus then desired his son to charge with his horse and light troops. The Parthians feigning flight drew them on, and when they were at a sufficient distance from the main army turned and assailed them, riding round and round so as to raise such a dust that the Romans could not see to defend themselves. When numbers had been slain, P. Crassus broke through with a part of the horse, and reached an eminence, but the persevering foe gave them no rest. Two Greeks of that country proposed to P. Crassus to escape with them in the night, but he generously refused to quit his comrades. Being wounded, he made his shield-bearer kill him; the Parthians slew all that were with him but five hundred, and cutting off his head set it on a spear.