Another good bit in Thucydides I found in Book VII.44, when the Athenians wanted to attack Epipolae in Syracuse. (I believe that's in Sicily; the Penguin edition has such poorly drawn maps as to actually be more useless than no maps at all.) They found they couldn't breach the line by day so they decided to attack at night. However it was a complete failure, a terrible rout, because there was a lot of confusion in the darkness. "But it was the singing of the paean which did them as much, or even more harm than anything, because of the uncertainty caused by having much the same paean sung on both sides. Thus when the Argives and Corcyraeans and other Dorian elements in the army started singing their paean they produced as much panic among the Athenians as the enemy did." I had thought that a paean was a hymn of praise, but it's clearly a battle song here.