History of the Peloponnesian War

When both sides were ready they came to close quarters. Demosthenes with the Messenians and a few Athenian troops had the right wing; the rest of the line was held by the Acarnanians, arrayed by tribes, and such Amphilochian javelin-men as were present. But the Peloponnesians and Ambraciots were mingled together, except the Mantineans; these were massed more on the left wing, though not at its extremity, for that position, which was opposite Demosthenes and the Messenians, was held by Eurylochus and the troops under him.

When finally the armies were at close quarters and the Peloponnesians outflanked with their left the right wing of their opponents and were about to encircle it, the Acarnanians, coming upon them from their ambush, fell upon their rear and routed them, so that they did not stand to make resistance and in their panic caused the greater part of their army to take to flight also; for when they saw the division under Eurylochus, their best troops, being cut to pieces, they were far more panic-stricken. And it was the Messenians, who were in this part of the field under the command of Demosthenes, that bore the brunt of the battle.

On the other hand, the Ambraciots and those on the enemy's right wing defeated the troops opposed to themselves, and pursued them to Argos; and indeed these are the best fighters of all the peoples of that region.