||The â€˜just warâ€™ doctrine, in history and political science, attempts to define moral criteria for the initiation of war (jus ad bellum: Latin, â€˜justice prior to warâ€™) and the conduct of war (jus in bello: Latin, â€˜justice during warâ€™). Attempts to develop just war criteria can be traced to classical Roman law, itself influenced by Greek and Hebrew philosophy. These ideas were systematized in European, Christian canon law (see Catholic political thought) in the early Middle Ages, and then developed further in the 16th and 17th centuries by jurists like Grotius. Key figures in the elaboration of criteria for a just war include St. Augustine in the 5th century, Thomas Aquinas in the 13th century, and Reinhold Niebuhr in the 20th.
The criteria for jus ad bellum are fourfold: first, the party who wages war must have sufficient authority to do so; second, there must be a just cause of offence, such as unprovoked aggression; third, there must be an intention to wage war solely for the sake of peace, or â€˜for the suppression of the wickedâ€™ and â€˜the sustenance of the goodâ€™; and fourth, there must be a reasonable prospect that the war can be won. The criteria for jus in bello, concern appropriateness of means to ends, and centre on notions like proportionality and discrimination.
The definition of a just cause for war is problematic because its legitimacy can be based on circular reasoning. Who has the authority to declare whether a war is just? The ruler? The people? What is the status of just war standards in a civil war? Even the justification of war to repel an unprovoked act of aggression is problematic because most acts of aggression or intervention are justifiable according to some moral or political claimâ€”for example, an historic national-territorial claim, or the protection of a stranded ethnic minority.
The traditional criteria for jus in bello are no less ambiguous. The decision to use force must be proportionalâ€”that is, force must do more good than harmâ€”but this criterion assumes that those who engage in war know how much destruction will occur before the war commences. The concept of proportionality attempts to limit the use of force to the amount necessary to achieve peace, yet such issues are inherently contestable: President Truman, for example, justified the use of atomic bombs against Japan in World War II by arguing that more lives would be saved if the war were brought to a sudden end. While Truman\'s argument may have been correct, the subsequent proliferation of weapons of mass destruction has significantly limited the scope of justifiable means because the potential destructiveness of war has increased significantly, and is much more likely to result in large-scale suffering for non-combatants.
The potentially anarchic nature of relations between states and the unpredictability of conflict-escalation may make moral criteria necessarily ambiguous and of limited (thought not insignificant) use in actually preventing or managing the conduct of war. However, just war criteria affect the decisions and actions of potential combatants, and have guided the Geneva Conventions, and the arbitration mechanisms imposed by the UN Security Council. BO\'L
See also utilitarianism.Further reading J.T. Johnson, Can Modern War be Just?; , M. Walzer, Just and Unjust Wars.