Endemic warfare is the state of continual, low-threshold warfare in a tribal warrior society. Endemic warfare is often highly ritualized and plays an important function in assisting the formation of a social structure among the tribes' men by proving themselves in battle.
Ritual fighting (or ritual battle or ritual warfare) permits the display of courage, masculinity and the expression of emotion while resulting in relatively few wounds and even fewer deaths. Thus one can view the practice as a standard form of conflict-resolution and/or as a healthy psycho-social exercise. Native Americans often engaged in this activity but warfare occurs or occurred much more rarely in most hunter-gatherer cultures.
Warfare is known to several tribal societies, but some societies develop a particular emphasis of warrior culture (such as the Nuer of South Sudan, the Māori of New Zealand, the Dugum Dani of Papua, the Yanomamö (dubbed "the Fierce People") of the Amazon, or the Germanic tribes of Iron Age Europe).
Endemic warfare is not equivalent to "primitive warfare" in general, but is reserved for perpetual low-threshold conflicts. Communal societies are well capable of escalation to all-out wars of annihilation between tribes. Thus, in Amazonas, there was perpetual animosity between the neighboring tribes of the Jívaro. A fundamental difference between wars enacted within the same tribe and against neighboring tribes is such that "wars between different tribes are in principle wars of extermination".
The Yanomamö of Amazonas traditionally practiced a system of escalation of violence in several discrete stages. The chest-pounding duel, the side-slapping duel, the club fight, and the spear-throwing fight. Further escalation results in raiding parties with the purpose of killing at least one member of the hostile faction. Finally, the highest stage of escalation is Nomohoni or all-out massacres brought about by treachery.
Similar customs were known to the Dugum Dani and the Chimbu of New Guinea, the Nuer of Sudan and the North American Plains Indians. Among the Chimbu and the Dugum Dani, pig theft was the most common cause of conflict, even more frequent than abduction of women, while among the Yanomamö, the most frequent initial cause of warfare was accusations of sorcery. Warfare serves the function of easing intra-group tensions and has aspects of a game, or "overenthusiastic football". Especially Dugum Dani "battles" have a conspicuous element of play, with one documented instance of a battle interrupted when both sides were distracted by throwing stones at a passing cuckoo dove.