History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
But that which put the Athenians at the greatest disadvantage and did them most harm was the singing of the paean; for the song of both armies was very similar and caused perplexity. Whenever, that is, the Argives or the Corcyraeans or any Dorian contingent of the Athenian army would raise the paean, the Athenians were just as much terrified thereby as when the enemy sang.
And so finally, when once they had been thrown into confusion, coming into collision with their own comrades in many different parts of the army, friends with friends and citizens with fellow-citizens, they not only became panic-stricken but came to blows with one another and were with difficulty separated.
And as they were being pursued by the enemy many hurled themselves down from the bluffs and perished; for the way down from Epipolae was narrow; and of those who in their attempt to escape got down to the level ground, the greater part, and especially those who belonged to the first expedition and therefore had a better acquaintance with the country, got through to the camp, but of those who had come later, some missed the roads and wandered about over the country, and these when day came were destroyed by the Syracusan cavalry, which were scouring the fields.
On the next day the Syracusans set up two trophies on Epipolae, one where the Athenian ascent was made, the other at the place where the Boeotians made the first resistance; and the Athenians recovered their dead under truce.
Not a few were killed, both of the Athenians and their allies; the arms taken, however, were out of all proportion to the dead, for while some of those who were forced to leap down the bluffs perished, some escaped.
After this the Syracusans, their earlier confidence now being restored as a result of their unexpected good fortune, sent Sicanus with fifteen ships to Agrigentum, which was in a state of revolution, in order that he might if possible win over that city; and Gylippus went out once more by land to the other parts of Sicily to secure additional troops, being in hope that he could even carry the walls of the Athenians by storm, now that the engagement on Epipolae had turned out thus.