Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

44. The whole army was soon in utter confusion, and the perplexity was so great that from¹ neither side could the particulars the conflict be exactly ascertained. In the daytime the combatants see more clearly; though even then only what is going on immediately around them, and that imperfectly—nothing of the battle as a whole. But in a night engagement, like this in which two great armies fought—the only one of the kind which occurred during the war—who could be certain of anything? [2] The moon was bright, and they saw before them, as men naturally would in the moonlight, the figures of one another, but were unable to distinguish with certainty who was friend or foe. Large bodies of heavy-armed troops, both Athenian and Syracusan, were moving about in a narrow space; [3] of the Athenians some were already worsted, while others, still unconquered, were carrying on the original movement. A great part of their army had not yet engaged, but either had just mounted the heights, or were making the ascent; and no one knew which way to go. For in front they were defeated already; there was nothing but confusion, and all distinction between the two armies was lost by reason of the noise. [4] The victorious Syracusans and their allies, who had no other means of communication in the darkness, cheered on their comrades with loud cries as they received the onset of their assailants. The Athenians were looking about for each other; and every one who met them, though he might be a friend who had turned and fled, they imagined to be an enemy. They kept constantly asking the watchword (for there was no other mode of knowing one another), and thus they not only caused great confusion among themselves by all asking at once, but revealed the word to the enemy. [5] The watchword of the Syracusans was not so liable to be discovered, because being victorious they kept together and were more easily recognized. So that when they were encountered by a superior number of the enemy they, knowing the Athenian watchword, escaped; [6] but the Athenians in a like case, failing to answer the challenge, were killed. Most disastrous of all were the mistakes caused by the sound of the Paean, which, the same being heard in both armies, was a great source of perplexity. For there were in the battle Argives, Corcyraeans, and other Dorian allies of the Athenians, and when they raised the Paean they inspired as much alarm as the enemy themselves; [7] so that in many parts of the army, when the confusion had once begun, not only did friends terrify friends and citizens their fellow-citizens whom they had encountered, but they attacked one another, and were with difficulty disentangled. [8] The greater number of those who were pursued and killed perished by throwing themselves from the cliffs; for the descent from Epipolae is by a narrow path. The fugitives who reached the level ground, especially those who had served in the former army and knew the neighbourhood, mostly escaped to the camp. But of the newly-arrived many missed their way, and, wandering about until daybreak, were then cut off by the Syracusan cavalry who were scouring the country.