War is a kind of collective, group, organization, faction, country, government mutual violence, attack, killing and other acts. It is an armed battle between the two hostile sides in order to achieve certain political, economic, territorial and other purposes. Since it is politicians rather than soldiers who trigger wars, wars are also regarded as extreme means of politics and diplomacy.

In a broad sense, it is not only human beings that have war. Creatures such as ants and chimpanzees also engage in war. War is the highest form of struggle among political groups, nations (tribes) and countries (alliances). It is the most violent means to solve disputes. It is one of the ways to solve problems in nature. It is usually considered as a method only used in primitive society. As the war of aggression caused great harm to human beings, it is not recognized in modern human society.

Source: @rafael_inked