International Relations Just War Theory
Scott A. Silverstone
  • LAST REVIEWED: 13 November 2018
  • LAST MODIFIED: 02 March 2011
  • DOI: 10.1093/obo/9780199743292-0050


The Just War tradition is based on the claim that only under certain conditions can war be morally defensible. Just War theory has claimed a middle ground between the realist tradition, which treats morality as irrelevant and even dangerous in the life and death stakes that political communities face in a threatening world, and pacifism, which rejects warfare under any conditions. Just War arguments are typically divided into two basic categories: the conditions that justify engaging in war (jus ad bellum) and the rules governing how war should be fought once it has started (jus in bello). Work on jus ad bellum emphasizes the moral appropriateness of fighting for a “just cause,” defined as defensive, and only as a last resort. The rules of jus in bello are meant to limit the extent of violence in war to what is proportional to the grievances that justify a particular war. Rules of jus in bello protect the lives of innocent civilians and combatants that no longer pose a threat, such as unarmed captives and the wounded, and limit the destruction of property. In recent decades increasing attention has been devoted to the moral rules that should guide how wars are ended (jus post bellum), specifically the political, social, and economic conditions left in the wake of war.

General Overviews

While moral claims about justice and war can be found in the literature of diverse cultures and in antiquity, its modern form is typically traced back to the 4th century writings of St. Augustine. The development of Just War theory in the centuries since Augustine can be understood as an effort by subsequent scholars to apply the work of earlier theorists to the specific experiences of warfare in their own time periods, or to modify or update Just War theory so that it is relevant to the changing political or technological features of war. There has been a surge of interest in Just War theory in recent decades, largely motivated by the American intervention in Vietnam. Other recent topics in Just War literature include the morality of nuclear weapons, the 1991 Gulf War against Iraq, the problem of politically motivated humanitarian crises and genocide in such places as Bosnia, Rwanda, and Kosovo, the justice of terrorism and counterterrorism, and the post-9/11 American interventions in Afghanistan and Iraq.

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