In this excerpt Dio Cassius is describing the March of Pompey in Iberia and Colchis.
The year following these exploits, in the consulship of Lucius Cotta and Lucius Torquatus, Pompey engaged in warfare with both the Albanians and the Iberians. Now it was with the Iberians that he was compelled to fight first and quite contrary to his purpose. They dwell on both sides of the Cyrnus, adjoining the Albanians on the one hand and the Armenians on the other; and Artoces, their king, fearing that Pompey would direct his course against him, too, sent envoys to him on a pretence of peace, but prepared to attack him at a time when he should be feeling secure and therefore be off his guard. Pompey, learning of this also in good season, invaded the territory of Artoces before the other had made sufficient preparations or had secured the pass on the frontier, which was well-nigh impregnable. In fact he had advanced as far as the city called Acropolis before Artoces became aware that he was at hand. This fortress was right at the narrowest point, where the Cyrnus flows on the one side and the Caucasus extends on the other, and had been built there in order to guard the pass. Thus Artoces, panic-stricken, had no chance to array his forces, but crossed the river, burning down the bridge; and those within the fortress, in view of his flight and also of a defeat they sustained in battle, surrendered.
Pompey, after making himself master of the pass, left a garrison in charge of it, and advancing from that point, subjugated all the territory this side of the river. But when he was on the point of crossing the Cyrnus also, Artoces sent to him requesting peace and promising to yield the bridge to him voluntarily and to furnish him with provisions. Both of these promises the king fulfilled as if he intended to come to terms, but becoming afraid when he saw his enemy already across, he fled away to the Pelorus, another river that flowed through his domain. Thus he first drew on, and then ran away from, the enemy whom he might have hindered from crossing. Upon perceiving this Pompey pursued, overtook, and conquered him. By a charge he came to close quarters with the enemy's bowmen before they could show their skill, and very promptly routed them. Thereupon Artoces crossed the Pelorus and fled, burning the bridge over that stream too;of the rest some were killed in conflict, and some while fording the river. Many others scattered through the woods and survived for a few days, while they shot their arrows from the trees, which were exceedingly tall; but soon the trees were cut down under them and they also were slain. So Artoces again made overtures to Pompey, and sent gifts. These the other accepted, in order that the king in the hope of securing a truce might not proceed any farther; but he would not agree to grant peace till the petitioner should first send to him his children as hostages. Artoces, however, delayed for a time, until in the course of the summer the Pelorus became fordable in places, and the Romans crossed over without any difficulty, particularly since no one hindered them; then at last he sent his children to Pompey and concluded a treaty.
Pompey, learning now that the Phasis was not far distant, decided to descend along its course to Colchis and thence to march to Bosporus against Mithridates. He advanced as he intended, traversing the territory of the Colchians and their neighbours, using persuasion in some quarters and fear in others. But, perceiving at this point that the route on land led through many unknown and hostile tribes, and that the voyage by sea was still more difficult on account of the lack of harbours in the country and on account of the people inhabiting the region, he ordered the fleet to blockade Mithridates so as to see that he did not sail away anywhere and to prevent his importing provisions, while he himself directed his course against the Albanians. He did not take the most direct route, but first turned back into Armenia, in order that by such a course, taken in connection with the truce, he might find them off their guard.