History of the Peloponnesian War

Having thus effected a union at day-break, they sat down at the place called Metropolis, and formed their encampment. Not long after, the Athenians came with their twenty ships into the Ambracian Gulf to assist the Argives; and Demosthenes arrived with two hundred heavy-armed of the Messenians, and sixty Athenian archers. The fleet therefore at Olpae blockaded the hill from the sea;

while the Acarnanians and a few of the Amphilochians (for the majority were forcibly detained by the Ambraciots) had by this time met at Argos, and were preparing to engage with the enemy, having appointed Demosthenes as commander of the whole army in concert with their own generals. He, having led them near to Olpae, encamped there;

a great ravine separating their armies. For five days they remained still, but on the sixth both sides drew up for battle. And as the force of the Peleponnesians was the larger, and outflanked his, Demosthenes, fearing that he might be surrounded, placed in ambush in a hollow way covered with a thicket, a body of heavy and light-armed troops, four hundred in all, that on the flank of the enemy which reached beyond his own, these troops might rise up in the very midst of the conflict and take them in their rear.

When the preparations were completed on both sides, they closed in battle. Demosthenes occupied the right wing with the Messenians and the few Athenians; while the remainder of the line was formed by the Acarnanians in their several divisions, and the Amphilochian dartmen that were present. The Peloponnesians and Ambraciots were drawn up without distinction, excepting the Mantineans, who kept together more on the left, though not in the extremity of the flank, for the extreme left was held by Eurylochus and his men, opposed to the Messenians and Demosthenes.