A battle cry or war cry is a yell or chant taken up in battle, usually by members of the same combatant group. Battle cries are not necessarily articulate, although they often aim to invoke patriotic or religious sentiment. Their purpose is a combination of arousing aggression and esprit de corps on one's own side and causing intimidation on the hostile side. Battle cries are a universal form of display behaviour aiming at competitive advantage, ideally by overstating one's own aggressive potential to a point where the enemy prefers to avoid confrontation altogether and opts to flee. In order to overstate one's potential for aggression, battle cries need to be as loud as possible, and have historically often been amplified by acoustic devices such as horns, drums, conches, carnyxes, bagpipes, bugles, etc..

Hakkapeliitta is a historiographical term used for a Finnish light cavalryman in the service of King Gustavus Adolphus of Sweden during the Thirty Years' War. Hakkapeliitta is a 19th-century Finnish modification of a contemporary name given by foreigners in the Holy Roman Empire and variously spelled as Hackapelit, Hackapelite, Hackapell, Haccapelit, or Haccapelite. These terms were based on a Finnish battle cry hakkaa päälle, commonly translated as "Cut them down!"