History of the Peloponnesian War

The result was that if a body of Athenians, even though superior in number, fell in with a party of the enemy, these would make their escape, inasmuch as they knew the Athenian watchword, whereas if they on their part could not give the answer they were put to the sword.

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.