Dio Cassius 49.20-22
20 In this way he met Pacorus in Syria Cyrrhestica6 and conquered him. For when he had not prevented them from crossing the river and had not attacked them at once after they had got across, they imputed sloth and weakness to the Romans and therefore marched against their camp, although it was on high ground, expecting to take it without resistance.
But when a sally was suddenly made, the assailants, being cavalry, were driven back down the slope without difficulty; and although at the foot they defended themselves valiantly, the majority of them being in armour, yet they were confused by the unexpectedness of the onslaught and by stumbling over one another and were defeated by the heavy-armed men and especially by the slingers; for these struck them from a distance with their powerful missiles and so were exceedingly difficult for them to withstand.
The fall of Pacorus in this struggle was a very great loss to them; for as soon as they perceived that their leader had perished, although a few men zealously fought for his body, yet when these also were slain, all the rest gave way. Some of them desired to escape homeward across the bridge and were unable to do so, being cut off and killed before they could reach it, and others fled for refuge to Antiochus in Commagene.
Ventidius easily brought into subjection all the rest out of Syria, which had been hesitating while awaiting the outcome of the war, by sending the prince's head about through the different cities; for the Syrians felt unusual affection for Pacorus on account of his justice and mildness, an affection as great as they had felt for the best kings that had ever ruled them.
And Ventidius himself made an expedition against Antiochus, on the plea that the latter had not delivered up to him the refugees, but really because of the vast wealth which he possessed.
21 When he had got to this point, Antony suddenly came upon him, and so far from being pleased, was actually jealous of him because he had gained the reputation of having carried out a brave exploit independently. Accordingly, he not only removed him from his command but employed him on no other business either then or later, although he himself obtained the honour of thanksgivings for both achievements and a triumph for his assistant's work.
The Romans in the capital voted these honours to Antony, on the one hand, because of his prominence and in accordance with the law, because he was the commander in charge; but they voted them to Ventidius also, since they felt that he had fully requited the Parthians, through the death of Pacorus, for the disaster which had been suffered by the Romans in the time of Crassus, especially since both events had taken place on the same day in both years.
And it turned out, in fact, that Ventidius alone celebrated the triumph, even as the victory had been his alone (for Antony perished in the meantime), and he acquired a greater reputation from this fact as well as from the caprice of fortune; for he himself had once marched in procession with the other captives at the triumph of Pompeius Strabo, and now he was the first of the Romans to celebrate a triumph over the Parthians.
22 This, to be sure, took place at a later period; at the time under consideration Antony attacked Antiochus, shut him up in Samosata and proceeded to besiege him. But when he found he was accomplishing nothing and was spending his time in vain, and when he also suspected that the soldiers were alienated from him on account of the disgrace of Ventidius, he secretly opened negotiations with the foe and made a pretended compact with him so that he might have a plausible reason for withdrawing.
At any rate, Antony got neither hostages (except two and these of little importance) nor the money which he had demanded, but he granted Antiochus the death of a certain Alexander, who had earlier deserted from him to the Roman side. After doing this he set out for Italy, and Gaius Sosius received from him the governorship of Syria and Cilicia.