Titus Livius (Livy), The History of Rome, Book 38
Evan T. Sage, Ph.D., Ed.

4. When the consul arrived before Ambracia, the siege seemed to him to involve great toil. [2] Ambracia lay at the foot of a rugged hill; the natives call it Perranthes. The city, where the wall turns towards the plains and the river, looks west; the citadel, which is situated on the hill, faces east. [3] The river Aretho, rising in Athamania, empties into the gulf of the sea which is called “the Ambracian” from the name of the neighbouring city. [4] In addition to the fact that the river on one side and the hills on the other defended the city, it was also protected by a strong wall, extending in circumference a little more than four miles. [5] Fulvius established two camps on the side of the plain, separated from one another by a moderate distance, and one redoubt on a high spot facing the citadel; [6] all these he planned so to connect by means of a wall and ditch that no [p. 15]egress from the city might be allowed the besieged¹ nor ingress from without to a relieving force. At the report of the siege of Ambracia the Aetolians had already assembled at Stratus in response to the edict of the praetor Nicander. [7] It had been their first intention to march from there with their entire force to prevent the siege; then, when they saw that the city was already in large part hemmed in by siege-works, and that the camp of the Epirotes lay on level ground across the river, they decided to divide their forces. [8] Eupolemus with a thousand light-armed troops, setting out for Ambracia, entered the city through the fortifications which had not yet been joined together. [9] It had been the original plan that Nicander, with the rest of the troops, should make a night attack on the camp of the Epirotes, which could not readily be aided by the Romans because the river was between them; [10] later, thinking that there was in the enterprise the danger that the Romans might somehow learn of it and he have no escape to a place of safety, he abandoned that design and turned aside to plunder Acarnania.