The word war has been used in the English language since the earliest times to denote conflict between human groups. However, this is a highly contested term and there is no one definition that fits all situations.

The term is used in both state and non-state contexts; it can refer to war fought between nations or to a state-led and -directed conflict. A state-based armed conflict is an armed conflict that involves two or more states, whereas a non-state armed conflict can involve any group that has an interest in conflict and uses armed forces as its primary means of coercion.

A number of different theories have been developed to explain the nature and the causes of war. Some of these theories are based on an analysis of the social structures that form a group and others are based on the biological aspects of man.

Socio-economic Approaches

Economic historians have tended to focus on the development of a competitive international system and have linked this to the rise of war as a tool for conflict management. They also consider that the increasing mobility of capital and information levels the distributions of wealth across societies, so that there are now relative, not absolute, differences in wealth that fuel war.

Technological Approaches

Technology has been a major source of war in the modern world. This has resulted in the development of munitions which can be delivered by aircraft, ships and missiles, which have changed the way war is fought.

This has led to the creation of highly organised militaries and to the use of proxies, informal groups of fighters who sometimes negotiate the control of resources, territory or conditions.

Despite these advances, the underlying principles of warfare remain. They are: fear, interest and honour.

These factors are governed by the needs of the group, and they are also influenced by the cultural institutions that shape man’s behaviour.

Individualist and Collectiveist Views of War

Some philosophers have argued that it is morally acceptable for groups to wage war against one another. But, like the reductivist/exceptionalist divide, this is a very difficult issue to resolve because it requires an examination of the broader social structures that form a group.

For example, does a group have independent interests that are not necessarily related to the welfare of its members? And does it have a social contract that informs its members of their duties and obligations to the group?

The problem with these approaches is that they tend to ignore the deeper cultural structures that can persist throughout history and even in current society.

Moreover, they tend to ignore the biological factors that have an impact on the decisions a group makes, whether to fight or not. Moreover, they are prone to overlook the inherited pugnacity of certain individuals or groups.

Ultimately, the best answer to these questions is a mixture of the various theories. It is not possible to separate the social, economic and technological factors that determine war.