The concept of war has been an important part of human understanding, as it has the ability to influence huge numbers of people, and the implications of it are wide-ranging. It is therefore essential that students of war carefully consider its definition. By doing so, they will be able to better understand the nature and the causes of this phenomenon.

While the definitions of war vary, they all share certain common features. These include the use of force, a potential threat of death, and the possibility of violence. They also reflect philosophical issues surrounding determinism. Some writers suggest that war is a result of a clash of arms, while others point to a state of mutual tension. Other writers describe it as a violent disease of the body politic.

Theories of war have gone through many phases throughout the past three centuries. From the early days of the Enlightenment, to the writings of Saint Augustine, to the theories of Karl von Clausewitz, war has been a focus of study. However, there are also many schools of thought who disagree about the role of morality in war.

The Oxford Dictionary defines war as a state of organized open-ended collective conflict. The United Nations Charter is a key international treaty regulating the use of force. This definition excludes low-level bombing campaigns. Also, it may be too broad. A working definition would include culturally evolved wars and guerrilla uprisings. In addition, it allows more flexibility than the OED version.

In the twentieth century, a number of different approaches were explored. These ranged from the psychological and legal to economic and technological. Each approach examined the various forms of conflict, and each sub-discipline grappled with the etiology of war.

Many of the more rationalistic theories of war highlight the importance of human reason and the effects of the human mind. For example, aristocratic societies were seen as virtuous, and warfare was often a means to extol these virtues. Others argue that war is a necessary component of the evolutionary process.

There are several schools of thought that oppose the idea of war as an instrument of national policy. These are known as moralists. These critics contend that the state should only engage in war when absolutely necessary. They also admit that war is used for peacemaking and to defend the state.

Another school of thought is known as communitarian. These authors claim that the Homeric war is not the same as the Sixteenth Century war. This view is based on the premise that cultural forms of life are persistent, and the Homeric war does not need to be replaced by modern conflict. Moreover, they reject the notion that individual humans are solitary and isolated.

While war is an all-pervasive phenomenon in the universe, its definition can be ambiguous. It can be an all-encompassing term that refers to a clash of arms, or a limited clash of interests between nation states. At the same time, it can be a limited instrument of national policy, and a political theory can be a way to define it.