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Just War Theory

Just War Theory. The term just war in its fullest sense refers to the broad tradition of interrelated theory and practice that defines for Western culture when the use of armed force for political purposes is justified and what limits or restraints ought to be observed in the employment of such force. Reflecting both the practical experience of war and normative thought on the place of force in statecraft, just war tradition first coalesced during the Middle Ages as a cultural consensus drawing on canon law, the dominant Augustinian theology and political theory, inherited Roman concepts of jus gentium and jus naturale, existing customs and practices of statecraft, and the code of chivalry. The roots of this tradition reach back through theology and law to classical Rome and Greece and to biblical Israel, and through chivalry to earlier Germanic conceptions of war and the soldier. The classical and biblical heritage was principally mediated to the Middle Ages by Augustine, who took the phrase “just war” itself (bellum justum) and a number of associated concepts from late Roman theory and practice, wedding them to a Christian ethic of intention based on love of neighbor and a concept of divinely instituted justice drawn from the Old Testament. Other elements of the medieval just war consensus traveled other routes. The result exceeded the sum of its parts both in content and in the breadth of its implications: a collection of restraints on war shaped by legal, moral, and practical concerns, and molded by the experience of war and statecraft.

This conception of just war sought to deal with two main concerns: the justification and limitation of the resort to armed force (in traditional terms, the jus ad bellum) and restraints on the actual employment of force (in traditional terms, the jus in bello). In its fullest and classic form, reached by the end of the medieval period, the jus ad bellum was defined by seven distinct requirements: just cause (defense, retaking something wrongly taken, punishment of evil); right authority (temporal rulers with no superior); right intention (no hatred of the enemy, desire for vainglory or power, bullying, etc.); the goal of peace; a reasonable hope of success; and the two conditions that the use of force in question achieve more good than harm and that the use of force be a last resort. The jus in bello took shape around two further requirements: that the force employed not cause more destruction than necessary, and the concept of immunity from harm for noncombatants, persons not directly involved in the waging of war.

In such form, just war tradition carried into the early modern period. Theorists like Vitoria, Suarez, Gentili, and Grotius assumed this concept of just war. Shakespeare displayed a remarkably complete knowledge of the conditions for just war in Henry V. Apologists on both sides of the post‐Reformation wars of religion employed just war criteria to argue the rightness of their respective causes. The early codes of military discipline which appeared in this period similarly reflected the influence of the inherited just war synthesis.

Yet while the tendencies of the Middle Ages were centripetal, those of the modern era have been centrifugal. Just war tradition in the modern period has been carried and developed not as a single entity but in the form of various distinct streams of thought and practice, sometimes in relation to one another, but more often moving according to their own logic.

One of the major streams of development of just war tradition through most of the modern period has been international law, from naturalists like Vitoria and Grotius through the juristic theorists to present customary and positive law. Contemporary positive international law on war includes a detailed jus in bello defined by the Geneva Conventions, the Hague Rules, various international efforts to limit or forbid use of certain weapons, and the findings of the Nuremberg and Tokyo war crimes trials, as well as a somewhat truncated jus ad bellum focused on the right of defense as defined in the United Nations Charter.

The development of military codes of conduct, theories and practice of limited war, and the persistence of the idea of chivalry in some form together make up a second major stream of just war tradition in the modern era. A landmark among the military regulations is the U.S. Army's General Orders No. 100 of 1863, a comprehensive code for conduct during war that strongly influenced both subsequent military codes and later positive international law on war. The limited war idea, operationalized in the “sovereigns' wars” of the eighteenth century, has emerged into new prominence in post–World War II military thought.

Within the sphere of religion, just war tradition remained acknowledged but without much attention or development through most of the modern period. In the last half of the twentieth century, however, led by American thought, a highly creative recovery of religiously based just war reasoning has taken place, responding to the strategic bombing of cities by both Axis and Allied powers during World War II, the development of nuclear weapons and strategic targeting doctrine, and the Vietnam War. This development within religious thought has in turn stimulated both the emergence of philosophical just war analysis and efforts to recover and understand historical just war tradition.

The recovery of just war thought in the religious sphere was largely initiated by the Protestant theologian Paul Ramsey, who in influential books and articles written mostly during the 1960s argued after the manner of Augustine for a conception of just war based in Christian love. Ramsey's historical context was the developing debates over strategic nuclear targeting and the initial stages of American involvement in Vietnam. Taking on various sorts of pacifists and others who argued that no contemporary war can be just because of the destructiveness of nuclear and other weapons, Ramsey insisted that there remains a place for responsible use of force by nations. Such a use, as he described it, would both serve justice and reflect the concerns of political prudence, traditional just war aims. The major focus of his work, though, was the just conduct of war. Hence he stressed the importance of discrimination (noncombatant immunity), which he understood as a direct requirement of Christian love, and the requirement of proportionality of means, an expression of political prudence.

Ramsey's importance for contemporary just war thought follows both from what he argued and from the partners he engaged in dialogue on just war terms: Protestant and secular pacifists; Catholic thinkers through detailed comments on papal and Vatican II statements on nuclear war; the secular policy community through debate with figures like Herman Kahn, Thomas Schelling, Robert W. Tucker, and many others; philosophers and theologians in America and other countries like Elizabeth Anscombe and Walter Stein in England. Though not himself a historian, he also encouraged historical efforts like those of James Turner Johnson to recover just war tradition as it existed and was applied to war in the past.

Use of just war categories and the effort to engage the policy community also characterize prominent recent church statements on ethics and war, such as the pastoral letters of the American Catholic bishops (1983) and the United Methodist bishops (1986). Both these documents, however, also nod significantly toward pacifism. The Catholic pastoral, for example, grounds just war thought in a presumption against war, while the Methodist document explicitly rejects war as incompatible with Christ's teachings and example. Both these concepts are at odds with the traditional Christian derivation of just war from the moral obligation to seek justice and protect the innocent.

In the philosophical sphere, the most important and most comprehensive recent treatment of just war ideas is Michael Walzer's Just and Unjust Wars. Aiming explicitly at recapturing just war reasoning for political and moral theory, this book develops the major traditional just war criteria through a mix of thematic analysis, utilitarian reasoning, and historical examples out of which the various just war principles arise as responses to evil in one or another concrete form. Like other modern just war thought, Walzer's analysis dwells heavily on the problem of ethical conduct during war; like positive international law, he treats the question of justification for use of force in the truncated terms of aggression and defense. Some of his most creative thought presses hard cases: whether the strategic bombing of German cities during World War II was justified by “supreme emergency,” for example. But on most matters Walzer concludes in or near the mainstream of the tradition, connecting especially strongly with developments in international law.

Recent military thought has also proved a fertile ground for recovery and development of just war thinking. Examples abound: Walzer's book has served as a text at the U.S. Military Academy; the service academies, the war colleges, and the National Defense University have sponsored various conferences and lectures examining or seeking to apply just war reasoning; a joint service committee on professional ethics provides a regular forum for consideration of just war and other ethical concepts related to the use of military force; revisions of the air force and army manuals on the law of war in the 1980s took close account of developments in international law on war and traditional principles like chivalry; the “Weinberger doctrine” of 1986 specifying conditions for commitment of American military forces closely correlates with the structure and elements of the content of traditional just war theory; and the formal justifications of the largest American military commitment since Vietnam, the Persian Gulf War, closely followed the form of just war tradition as found in international law, while the conduct of that war in numerous ways reflected the debate over ethical conduct in war developed in just war terms over the previous three decades.

Contemporary just war thinking is challenged in three major ways: by the growth of pacifist rejection of all war; by the question of how to relate historical just war tradition to contemporary international politics and war; and by the growing problem of cultural relativism, which challenges the universality of just war principles and sets up alternative traditions as guides for international conduct in the use of force.

Yet, as the above religious, philosophical, military, and legal examples show, just war tradition is deeply embedded in Western culture and is particularly vigorous in recent American debate over the proper role, structure, and use of armed force. Contemporary American discourse on war reflects both the traditional just war categories and the content of those categories, mediated through the streams of modern thought that have carried this tradition. By merging these streams in a common debate, moreover, recent American just war thought has tended to reestablish their relationship as elements of a broader tradition, re storing a synthesis approach to just war long absent in Western thought.
[See also Aggression and Violence; Academies, Service; Bombing, Ethics of; Bombing of Civilians; Disciplinary Views of War; Laws of War; Religion and War; Rules of Engagement; War: Nature of War.]


Paul Ramsey , War and the Christian Conscience, 1961.
Paul Ramsey , The Just War, 1968.
Frederick H. Russell , The Just War in the Middle Ages, 1975.
Michael Walzer , Just and Unjust Wars, 1977, rev. ed. 1992.
Stanley Hoffman , Duties Beyond Borders, 1981.
James Turner Johnson , Just War Tradition and the Restraint of War, 1981.
William V. O’Brien , The Conduct of Just and Limited War, 1981.
National Conference of Catholic Bishops , The Challenge of Peace, 1983.
James Turner Johnson , Can Modern War Be Just?, 1984.
James Turner Johnson , Moral Issues in Contemporary War, 1999.

James Turner Johnson

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