War is a behavior pattern of organized violent conflict, typified by extreme aggression, societal disruption, and high mortality. This behavior pattern is found in many primate species, including humans, and also found in many ant species. It involves two or more organized groups. Such a conflict is always an attempt at altering either the psychological hierarchy or the material hierarchy of domination or equality between such groups. In all cases, at least one participant (group) in the conflict perceives the need to either psychologically or materially dominate the other participant. Amongst humans, the perceived need for domination often arises from the belief that an essential ideology or resource is somehow either so incompatible or so scarce as to threaten the fundamental existence of the one group experiencing the need to dominate the other group. Leaders will sometimes enter into a war under the pretext that their actions are primarily defensive, however when viewed objectively, their actions may more closely resemble a form of unprovoked, unwarranted, or disproportionate aggression.