You know how, at various points in The Return of the King, Merry and/or Pippin will shout “for the Shire!” or “for Frodo!” before running to battle and certain death? Did ancient warriors really do this or is it artistic license?
Cry God For England, Harry and St George!
If it’s just artistic license, it’s certainly old artistic license. It’s even in Homer.
Lots of historic info here: Battle cry - Wikipedia
Including ancient Greeks mimicking owls in their battle cry.
ETA2: In eras in which the primary determination of who won the battle was often who was feeling brave enough to run headlong to death and not turn tail and run away, it makes sense that a loud, rousing cry of inspiration would be a standard part of the battle plan.