War is defined as a state of usually open and declared armed hostile conflict between states or nations but also the period of such armed conflict as well as a state of hostility, conflict, or antagonism or a struggle or competition between opposing forces or for a particular end. War also describes the art or science of warfare. In Western tradition, there is a sense that the reasons for war must be just. This idea dates back to ancient times.
To St. Thomas Aquinas, a war must be just in both the reasons for going to war and how war is fought. Reasons for going to war—jus ad bellum—are just if
- (1) war is declared by an appropriate authority;
- (2) the war is waged for a just cause; and
- (3) the war is waged for just intentions. An appropriate authority is a proper, governing authority. A “just cause” may include self-defense or a response to injustice. “Just intentions” mean that it must not be fought for self-interest, but for justice or a common good. In addition,
- (4) there must be a reasonable chance of success;
- (5) the good that will be achieved must outweigh the bad; and
- (6) war must be a last resort.
- War, in the popular sense, a conflict between political groups involving hostilities of considerable duration and magnitude. In the usage of social science, certain qualifications are added. Sociologists usually apply the term to such conflicts only if they are initiated and conducted in accordance with socially recognized forms. They treat war as an institution recognized in custom or in law. Military writers usually confine the term to hostilities in which the contending groups are sufficiently equal in power to render the outcome uncertain for a time. Armed conflicts of powerful states with isolated and powerless peoples are usually called pacifications, military expeditions, or explorations; with small states, they are called interventions or reprisals; and with internal groups, rebellions or insurrections. Such incidents, if the resistance is sufficiently strong or protracted, may achieve a magnitude that entitles them to the name “war.”
- War is generally defined as violent conflict between states or nations. Nations go to war for a variety of reasons. It has been argued that a nation will go to war if the benefits of war are deemed to outweigh the disadvantages, and if there is a sense that there is not another mutually agreeable solution. More specifically, some have argued that wars are fought primarily for economic, religious, and political reasons. Others have claimed that most wars today are fought for ideological reasons. In the United States, the legal power to declare war is vested in Congress; however, the president is the commander-in-chief of the military, so he or she holds power to conduct a war once it has been declared. In many instances, the president has used military force without declaring war.