Is the Doctrine of Pre-emption

a Legitimate Element of the Just War Tradition?



presented to the

Joint Services Conference on Professional Ethics

Washington, DC

27 January 2005


Robert G Kennedy, PhD

Professor of Management

and Catholic Studies

University of St Thomas

Mail #55-S

St Paul, MN 55105

VOX: 651 962 5140                           FAX: 651 962 5710





The present-day conception of “aggression,” like so many strongly influential conceptions, is a bad one. Why must it be wrong to strike the first blow in a struggle? The only question is, who is in the right?

G E M Anscombe

“War and Murder” (1961)


The line between legitimate and illegitimate first strikes is not going to be drawn at the point of imminent attack but at the point of sufficient threat. The phrase is necessarily vague. I mean it to cover three things: a manifest intent to injure, a degree of active preparation that makes that intent a positive danger, and a general situation in which waiting, or doing anything other than fighting, greatly magnifies the risk.

Michael Walzer

Just and Unjust Wars (1992)





ust war theory is commonly, and rightly, seen to be an alternative both to pacifism and to permissivism (which denies that war needs to be justified if it is expedient). What is not so clearly seen is that the tradition of just war thinking is not a singular body of thought maintained over the centuries but rather a collection of traditions, each sharing some common elements and each having its distinctive characteristics. Contemporary discussions about war, while still involving pacifist and permissivist voices, can be particularly vexed among those who claim to speak within the just war tradition. Passionate disagreements about what is just and unjust seem more characteristic of these discussions than widespread consensus.


These difficulties pertain both to jus ad bellum and jus in bello criteria (the recent conflicts about torture and interrogation techniques being an example of the latter). While important problems persist in regard to issues of legitimate authority as well as right intention (two of the three traditional jus ad bellum criteria), our purpose in this paper will be to examine a particular aspect of the criterion of just cause, specifically the question of whether a nation may ever justly attack another nation which appears to threaten grave harm to the first. To do this we will first consider the characteristics of the different versions of the just war tradition with a view to clarifying the foundations of an answer to the problem.


Four Traditions of Just War Thinking


It seems likely that as long as man has engaged in war, he has raised questions about the justice of his actions. In the West, the reflections provoked by these questions led to the development of the just war tradition. Over more than 2,000 years, this tradition has been shaped by differing political and philosophical contexts. At least five distinct versions, or traditions, can be identified.[1]


The Ancient Tradition


In the West, systematic thinking about the justice of war goes back at least to the ancient Greeks, and the time of Socrates, Plato, and Aristotle. To the Greeks and Romans, it was difficult to conceive of the world as a human community. It was instead a world of great diversity: of languages, of laws and customs, of gods and religions. It was a world of conflict and competition, where the weak were far too often at the mercy of the strong. Nevertheless, it was also a world in which questions of justice were posed.


Aristotle understood that peace is much to be preferred over war, and that civil leaders ought to direct every effort (including military activities) to the establishment of an enduring peace.[2] Nevertheless, he acknowledged that war is at times necessary and that a community ought to be prepared for it. He denied that waging war in order to dominate one’s neighbors was “useful or right,” nor should a community go to war to enslave another community that does not deserve to be enslaved. Legitimate reasons for war were defense of the community, the extension of empire for the sake of those who would be governed, and the enslavement of those people who deserved to be enslaved. (These last two causes did not find their way into classic just war theory!)


Though the Greek philosophers brought order to so many branches of learning, they did not develop a detailed framework for thinking about the morality of war. That remained for the Romans, who were perhaps more deeply motivated by their passion for law. In the writing of Cicero and other Roman thinkers we find the basic elements of what we recognize as just war criteria, particularly the need for legitimate authority and a just cause.[3] On Cicero’s view, a war is unlawful unless formally declared and provoked by the need either to defend the community or to recover what has been taken.


On one level, the concern for justice had a religious foundation in this period. The Greeks and the Romans, quite like the uncivilized peoples with whom they were often at war, were concerned about the will of the gods. War has always been a serious undertaking and it was normal to make some effort to determine whether the gods favored a prospective war. Various customs developed to address this concern and they persisted even after the leaders involved no longer worried much about being assured of the gods’ favor.


By the time of Cicero, however, and under the influence of Stoic thought, the concept of a jus naturale, a natural law, began to influence thinking about justice. Whether or not the gods interfered directly in the affairs of men, there was nonetheless a law that measured human actions. This law of nature was not the creation of human minds and there were always consequences of violating it. As a result, it was important to consider serious decisions like war in light of this natural law. Choices that violated this law would not turn out well.


One implication of this theory of law was its universality. Given a law of nature binding on all rational beings, there must be a fundamental equality between peoples and communities. As a result, Cicero and the Stoics rejected the Greek view that some people were slaves by nature and that more civilized peoples could legitimately make them slaves in fact. Such an objective could never be a lawful reason for going to war.


Strictly speaking, the just war tradition did not begin as a tool for constraining war-minded leaders. The Greeks and the Romans both regarded war as a normal part of human life, even as they recognized that there were many bad reasons for engaging in it. Wise leaders would seek to avoid war but they also knew that sometimes war could not or should not be avoided. The ancient just war tradition, such as it was (and it was never developed in great detail), was an attempt to think about the circumstances in which war could be pursued in conformity to the natural law.


The fact that a great many wars in the ancient world, perhaps the vast majority, were not just in light of this tradition does not invalidate its legitimacy.


The Augustinian Tradition


Though not the first Christian thinker to turn his attention to the question of the moral legitimacy of war, Augustine was particularly influential, especially in the Latin church. He appropriated what was by then a set of familiar categories and recast and augmented them in light of Christian moral theology. He brought to the discussion a Roman realism about the inevitability of war as a feature of human life, but he explained this inevitability as a consequence of original sin. As one scholar has observed, “Wars are inevitable as long as men and their societies are moved by avarice, greed, and lust for power, the permanent drives of sinful men.[4]


For Augustine, as for Aristotle and Cicero, the ultimate objective of war is peace. But Augustine understood peace, which he defined in the classic phrase, tranquilitas ordinis, the tranquility of order, as something more profound than what his predecessors imagined. War is occasioned, and may be rightly pursued (other conditions being satisfied) when the proper order of the human community is disrupted. In general, he said in a phrase much quoted in later centuries, a just war is one which seeks to redress or avenge injuries (ulciscuntur iniurias).


Augustine was under no illusion about most of the wars in the earthly city, which were waged not to establish authentic peace but to secure domination. Whatever peace resulted from this was merely a temporary respite from further fighting. Still, war might be lawfully waged if it aimed at the defense of the community or at the punishment of a state which refused to return property that it had taken or to make reparations for the harms it (or its subjects) had done.


Augustine’s formulations shaped the medieval discussion of lawful. This discussion was pursued by two groups, scholars of law and theologians. While these two groups maintained contact with one another they nevertheless pursued their development of the tradition independently. Though the lawyers are less well known, they had a keener interest in the topic and produced a more systematic framework.[5] Concerning the matter of just case for war, there was common agreement that war could be pursued to “repel invasion, to recover property, and to avenge prior injuries.”[6]


The lawyers also discussed the issue of proper authority. There was common agreement that no civil leader had authority to wage war if he himself had a superior, but this commonality broke down when it came to applying the principle to concrete cases.[7] The Middle Ages were a period in which the authority of the emperor was not an empty idea, but in which it was increasingly difficult to acknowledge that authority as effective. By the 13th century, changes in political structure that would lead to the modern nation-state were well under way. These changes entailed the demise of imperial power and authority in much of western Europe, and so the lawyers differed as to who, in fact, possessed the authority to declare war. In the end, though, the principle remained intact—that only a civil authority without a superior could declare war—even if the application was in dispute.


On the theological side, Thomas Aquinas (1224-1274) would adopt Augustine’s thinking and neatly summarize it in the three familiar jus ad bellum criteria: legitimate authority, just cause and right intention. Beyond this he added relatively little to the development of the just war tradition. Aquinas’s only treatment of the topics of law and war are to be found in his Summa theologiae.[8] His influence on the Scholastic discussions of law and war was, in some sense, out of proportion with the very brief attention he gives to the topics in his six-million-word body of work. No doubt this is a consequence of his towering reputation as a theologian, but one effect of this is that the very real development of these topics that his early modern successors achieved is often overlooked.


The Natural Law Tradition[9]


The two streams of thought that worked their way through the Middle Ages, the legal and the theological, came together in a number of Catholic and Protestant writers working in the 16th and 17th centuries.[10] Whatever their particular differences might have been, they all worked within a more or less commonly accepted tradition of natural law, and drew the framework for their consideration of lawful war from the work of their Ancient and Augustinian predecessors.[11]


This tradition begins with the well-known distinction between natural and positive human law. On this view, natural law is a regularity in human affairs that is recognized by right reason but which is not, strictly speaking, the creation of the human mind. For free human choices, natural law is the analog of physical law for inanimate bodies. A stone has no choice but to conform to the physical law of gravity, for example, and human persons, though they may choose freely to violate the natural law, cannot do so with impunity. It was in this conceptual context that the authors of the Natural Law tradition set out to examine the question of lawful and just wars.[12]


They first distinguished between aggressive war and lawful war, where aggressive war was pursued for one or more of the unjust purposes that earlier tradition identified, such conquest, greed, and so on.


In the category of lawful war, they further distinguished between defensive and offensive wars, a distinction that has not been continued in modern discussions of just war theory. On their account, a defensive war is one which is waged to repel an unjust attacker or to prevent such an attack from occurring. By contrast, an offensive war is one which seeks to remedy a wrong that has already occurred.


For example, if a nation should come under attack, the war it pursues to thwart the attacker at the time of the attack, or to prevent the attacker from succeeding in his attempt to seize its territory, is a defensive war. Should the attacker be successful in occupying the other nation’s territory, the occupied nation (and its allies) might very well still be justified in taking military action to force the aggressor to quit the occupation. In such a case, though, the war would be offensive.[13] A similar distinction would hold in the situation of an individual resisting a burglar caught in the act and that same individual attempting to recover stolen property from the burglar at a later time.


In every case, however, whether defensive or offensive, no war may be lawfully waged unless there has been a prior wrong.[14] The absence of a prior wrong would put military action into the unlawful category of aggressive war.


The Natural Law theorists also considered the question of proper authority. They typically addressed the question by acknowledging that the law of nature gives each individual the right to defend himself against attack, and that princes and nations possess the same right. Thus Suarez could say, “I hold . . . that a sovereign prince who has no superior in temporal affairs, or a state which has retained for itself a like jurisdiction, has by natural law legitimate power to declare war.”[15] Other writers would add the qualification that a subordinate prince (or state) has a contingent authority to declare war in the event that the superior to which it is bound is negligent in vindicating the rights of the subordinate.


More directly related to the topic of this paper is the question of whether the Natural Law theorists would consider pre-emptive military action to fall within the category of lawful war. Other relevant conditions being met, it is clear that in their minds pre-emptive action can indeed be lawful, and lawful as a matter of defensive war.


A very strong case (probably too strong) is offered for this position by Alberico Gentili (1552-1608).[16] He wrote, “One ought not to delay, or wait to avenge at one’s peril an injury which one has received, if one may at once strike at the root of the growing plant and check the attempts of an adversary who is meditating evil.”[17] And again, “A defense is just which anticipates dangers that are already meditated and prepared, and also those which are not meditated, but are probable and possible.”[18]


Harsh words, for they suggest that a nation may be justified in beginning a war on the suspicion that another nation may be preparing for war, or doing no more than developing the capacity for war. In the same chapter in which he makes these remarks, however, Gentili tempers them by noting that fear alone does not make a cause for war just.


A more typical treatment can be found in Grotius, who observes “A just cause then of war is an injury, which though not actually committed, threatens our persons or property with danger.”[19] He adds further, “The danger must be immediate, which is one necessary point. . . . But they are themselves much mistaken, and mislead others, who maintain that any degree of fear ought to be a ground for killing another, to prevent his supposed intention.”[20]


In sum, it may be lawful to bring an attack against another nation if that other nation poses a serious and “immediate” threat to the persons or property of one’s own nation.


While the Natural Law theorists are prepared to defend this position, they are not entirely comfortable with its implications. The obvious difficulty is that the authority who must decide to begin the war may very well not be in a position to know with certainty that the enemy is about to attack. Our writers are generally agreed that fear of attack is not in itself sufficient to provide a just cause, despite Gentili’s comments. On the other hand, this same authority has a duty to protect his people and their property.


Suarez addresses this question directly and insists that the prince or other authority must examine the facts diligently and make every effort to avoid war.[21] He ought to consult others to ensure that he is judging the situation correctly. If he does make such a diligent examination, free from personal prejudice as to the outcome of the examination, and is supported in his judgment by wise and just counselors, then he is morally free to move forward.


The Modern Tradition


It is worth noting that just war thinking is not merely an academic exercise; it is thinking about practical morality and it has (or is intended to have) practical consequences. As such it is also in every era influenced by practical realities, from political structures to technologies to religious convictions. The history of just war thinking suggests that, while its fundamental principles may be preserved from one period to another, the application of these principles is subject to variation.


This description, though, may not be entirely true of the modern period. In one’s own time it is always difficult to see the general characteristics and trends that will be so obvious to later historians. Still, it seems to me that there is probably no such thing as a unified modern just war theory. No doubt, there are any number of voices who embrace the concept of a just war but it is not clear (to me at least) that there is common agreement on the philosophical foundations or the conceptual details. More is at stake here than simply disputes about particular applications of principle; I think there are disputes about the principles themselves.


I realize that any attempt to describe in a general way what we might call the Modern tradition will certainly be open to objection, but then a comprehensive description is not the purpose of this paper. Nevertheless, I believe there are some features of the contemporary discussion of just war theory that distinguish it from earlier traditions. In what follows, I will try very briefly to identify some of these features.[22]


One important characteristic of the modern discussion is the abandonment of a natural law foundation for the theory in favor of grounding it instead in positive international law. This is in sharp contrast with the theorists of the Natural Law tradition, who were also engaged in crafting a theoretical framework for positive international law, and who understood positive law to be subordinate to natural rights. International law, on their view, could (and should) provide for the resolution of disputes between nations but it could not extinguish the natural right of nations to provide for their own defense against aggressors. It seems as though for many contemporary just war theorists the right of self-defense is not understood to be natural but rather to be a creation of international law, and therefore subject to the constraints of law. While nations may be sovereign as regards their domestic affairs, they are not autonomous as regards defense of the common good.


Another feature is just this commitment to national sovereignty as regards domestic affairs. In the Augustinian and Natural Law traditions princes and states were not considered to be entirely immune from interference in their domestic affairs and it was considered legitimate for others to come to the aid of peoples living under an oppressive ruler. Furthermore, the Augustinian idea that all just war has a punitive character survived to some degree even in the Natural Law tradition and grounded the conviction that princes and states could be punished by other states for their misbehavior. Needless to say, contemporary just war theory does not welcome this view and the practice of the international community (e.g., Bosnia, Ruanda, the Sudan, etc) reflects this.


Similarly, the question of legitimate authority has been obscured by the ambiguous position of the United Nations. The just war tradition, in both its Augustinian and Natural Law versions, could very well accommodate a supra-national authority (an emperor or pope, for example) which could replace national leadership as a legitimate authority in resolving disputes and declaring war. At the same time, writers in these traditions were quite clear that a community’s right of self-defense was not extinguished but merely replaced by the duty of the superior authority to provide security and vindication of rights. In cases of negligence or failure on the part of the superior authority, the inferior community’s right to declare and wage war was revived. The evident failure of the United Nations to provide security and to vindicate rights is often not taken in the modern discussion to be an abdication of its authority with regard to war.


Finally, there is in the modern conversation a quite rational apprehension about the destructive power of war. In a civilization traumatized by the horrible experiences of two world wars and the development of weapons of indiscriminate and mass destruction, the problem of proportionality seems to have crowded out the question of justice. If no war can be limited in scope, as seemed to many in the closing decades of the twentieth century to be the case, then can any cause sufficiently justify war? And if not, has the just war tradition, in all its forms, become nothing more than an historical relic?[23]


One consequence of this is the contemporary conviction that only defensive wars can be just.[24] If this were so, then the entire category of lawful offensive war is abandoned in the modern tradition and military actions undertaken to recover what has been stolen (e.g., Kuwait 1991) or to punish an aggressor (e.g., Baghdad 1993) must be regarded as unjust.


If this description is reasonably accurate, or if it describes a trend in modern just war thinking, then it seems to me that the modern tradition does constitute a rejection of important elements of classic just war thinking. Unfortunately, the result, I think, will be increased polarization in discussions about the use of military force, toward the extremes of pacifism and permissivism.[25]


This need not be the case. The modern tradition, shaped as it has been by the Cold War, may not contain the resources to deal effectively with new challenges posed by asymmetric warfare and international terrorism. Classic just war thinking, however, constitutes a theoretical framework that is robust enough to contend with the unique problems of modernity. The question of lawful pre-emption is an example.


Pre-emption: An Application of the Classic Tradition


As established above, the Natural Law tradition of just war thinking accommodates a situation in which one state lawfully strikes at another in an attempt to prevent unjust aggression, a kind of anticipatory defensive war. The consensus among the theorists of this tradition is that the state which makes the pre-emptive attack must be quite sure that the attack is planned and that it would take place in the very near future unless prevented. They are aware that there is a problem concerning the objectivity of a leader considering a pre-emptive attack, but they are content to say that if the leader has made a diligent inquiry, is sure of his facts, has no reasonable alternative to war, and is motivated by the right intention of protecting his people, he acts lawfully. They also acknowledged that anxiety that an enemy might someday be in a position to do unjust harm does not constitute sufficient reason for going to war. All in all, this seems not to have been a controversial matter among them.


Building upon this position, I would like to propose a modest development of the doctrine of lawful pre-emptive war and to distinguish it from what has come to be called “preventive” war.


Assuming legitimate authority and right intention, the key question concerning pre-emptive action has to do with just cause. We may sketch out the conditions for lawful action according to the common just cause categories of prior wrong, proportionality, prospect of success, and last resort.


1.         Prior Wrong: The decision maker must know beyond a reasonable doubt that the enemy a) possesses the capacity to do serious harm, b) actively wills to do such harm unjustly, and c) is making progress in a series of steps actually aimed at doing such unjust harm.


A community is actually harmed when it is threatened with serious injury. It is not the case that the community must actually suffer an injury before the criterion of prior wrong is satisfied. However, the threat in the relevant sense if an enemy merely possesses the capacity and has the will to use that capacity. The enemy must actually begin taking steps aimed at implementing his harmful intent, even if the process is a long one.


2.         Proportionality: The wrong threatened cannot be minor. The use of military force must not be significantly more damaging to all concerned (with special consideration given to civilians) than the unjust harm prevented by the action.


For example, Augustinian and even Natural Law theorists were sometimes willing to accept challenges to the honor of a prince or a nation as proportionate to war. We are unlikely to do so, but we can recognize that failure to respond in some proportionate way (which might include the very limited use of military force) to minor provocations may lead enemies to conclude that a nation is vulnerable to much more serious attacks. Other conditions being satisfied, such proportionate responses would be lawful.


3.         Prospect of Success: It must be reasonable to conclude that pre-emptive action can effectively impede or interrupt the series of steps begun by the enemy that will eventually result in unjust harm.


4.         Last Resort: The distinctive character of pre-emptive action is especially evident in the application of the criterion of last resort. In general, this criterion is satisfied if it is reasonably judged that the series of steps leading to unjust harm cannot be impeded or interrupted by any available means other than military action.


In this context, we must consider the problem of what it means to say that an attack must be imminent. The Natural Law theorists who discussed this, as we have noted, generally said that the fear of attack was not enough to provide just cause. Some, like Grotius, said that the prospect of attack must be immediate. Which is usually taken to mean that pre-emptive action becomes lawful when an unjust attack is only a short time away. In technically primitive societies this might be all we need to say. However, in the modern situation, characterized as it is by international terrorism, it is necessary to define imminence more precisely. It cannot simply mean that something is about to happen in a short period of time.


I suggest that the relevant meaning of imminence has to do with the concept of a series of steps to be undertaken in order actually to bring about unjust harm. This harm is imminent when the process approaches the point in the series of steps after which it is not possible for the target community to prevent the harm from occurring.


For example, suppose that a nation possesses the capacity to launch a missile from a submarine with significant destructive capability. A series of steps must be taken before actual harm can be done to anyone. The submarine must travel to a suitable launch site, the missile must be prepared and programmed, the launch sequence must be executed, and so on. Assuming that the target possesses not effective missile defense, the point after which it is impossible for the target to prevent the harm is the moment of launch. This is likely to be a relatively short time before the harm is actually suffered.


But suppose a different scenario. Imagine a situation in which a nation possesses a compact nuclear weapon that it is willing to sell. Suppose, too, that there is a buyer representing an international terrorist organization. Once the weapon has passed into the hands of the terrorists it is likely that the target community can no longer frustrate their intention to do them unjust harm. As a consequence, the threat becomes imminent at the point at which such a transfer takes place, even though this might be days, months, or even years before the actual harm is done.



To summarize, I believe it is consistent with the Augustinian and Natural Law traditions of just war thinking—though perhaps not with the Modern tradition—to conceive of the lawful, pre-emptive use of military force along the lines just described.


Such pre-emptive action must, however, be distinguished from preventive action, which would ordinarily not be lawful. Preventive action would be action undertaken in the absence of a just cause, as defined above. That is to say, it would be action when an enemy does not possess the capacity to do serious harm (though we may think he would like to develop such a capacity), or when he does not actively will to do such harm (though we fear he might someday choose to do so), or when he has not initiated a series of steps leading to such unjust harm.


In the Augustinian and Natural Law traditions, preventive war was commonly thought to be provoked by fear and the majority of thinkers in these traditions rejected it as unlawful and unjust. Pre-emptive war, on the other hand, was commonly regarded as lawful and just as a species of defensive war, provided the ordinary conditions for just war were satisfied. This may indeed not find a place in modern articulations of just war theory, but perhaps it should. There is a deep traditional foundation for its legitimacy and contemporary conditions that urge us to reconsider it as a genuine example of just war.




[1] A cautionary note: It is tempting to imagine a line of progress running through the different versions of the tradition, as if later versions simply augment or correct earlier versions. This may be true in some specifics, but it is also true that, in other ways, later versions sometimes lack the sophistication of earlier versions. It might be better to understand the latest versions as bodies of thought shifted to parallel tracks by changes in political experiences and dominant philosophical approaches.

[2] Politics, Book VII, chapter 14.

[3] Cicero’s essay, On the Commonwealth (De respublica), has survived only in fragmentary form. Other ancient witnesses permit scholars to reconstruct elements of the missing sections, which include his discussion of lawful war. See, for example, one such reconstruction in Cicero: On the Commonwealth, translated and edited by G H Sabine and S B Smith (Indianapolis: Bobbs-Merrill, 1929).

[4] Herbert A Deane, The Political and Social Ideas of St Augustine (New York: Columbia University Press, 1963), p 155. Chapter 5 of this excellent book is devoted to Augustine’s thought on war. Another helpful resource for the study of Augustine on war is John Langan, SJ, “The Elements of St Augustine’s Just War Theory,” The Journal of Religious Ethics 12 (1984) 19-38.

[5] A good, though not unbiased, treatment of the medieval canonical development of just war theory is Frederick H Russell, The Just War in the Middle Ages. (Cambridge: Cambridge University Press, 1975).

[6] Russell, Just War, p 64.

[7] See Russell, Just War, pp 298-299.

[8] The treatment of law is found in Summa theologiae, IaIIae, qq 90-97. The discussion of war is found at Summa theologiae, IIaIIae, q 40. It is noteworthy that while Aquinas returns to many subjects more than once in his body of work, he does not turn to these topics anywhere else.

[9] Much of the critical work done on the topic of international law, within which the subject of lawful and just wars was addressed, took place in the 16th and 17th centuries, and was brought into its final form in the 18th century. Key thinkers in this period included both Catholics and Protestants. On the Catholic side, prominent names include Francisco Vitoria (1485-1546), Francisco Suarez (1548-1617), and Alphonsus Liguori (1696-1787). On the Protestant side, Hugo Grotius (1583-1645), Samuel Pufendorf (1632-1694), and Emmerich de Vattel (1714-1767). Theological differences inclined both groups to develop their thinking along somewhat different lines but in relation to our subject there is a great deal of consistency. As a result, I have chosen to treat them as a unified group because of them common commitment to the concept of natural law as a foundation for their work.

[10] For the study of the writers in this tradition, the series of volumes, The Classics of International Law, produced under the auspices of the Carnegie Endowment for Peace and under the general editorship of James Brown Scott are indispensable.

[11] We generally speak of the “just war” tradition and while the writers in this category also spoke of the justice of wars, it be fairer to say that their first concern was to establish the lawfulness of war, rather than its justness. Lest this seem like a distinction without a difference, we might note that the justness of a war if concerned primarily with the nature of the cause that provokes the war, while the lawfulness of a war concerns the entire set of factors that might make a war morally legitimate.

[12] Though older, an excellent article examining this tradition is Joachim von Elbe, “The Evolution of the Concept of the Just War in International Law,” American Journal of International Law 33 (1939) 665-688.

[13] The circumstances of the First Gulf War of 1991 illustrate this distinction. Efforts made by the Kuwaitis in August 1990 as the Iraqis invaded were properly defensive. The attack launched in January 1991 was, according to the definitions offered by the Natural Law tradition, was offensive since it sought to recover territory already taken and occupied. The Natural Law theorists, by the way, did not insist on a temporal limitation as a condition for a just cause in an offensive war. That is, a just offensive war might be begun months or years after the aggressive event that provokes it. Thus, French efforts in 1944 to recover territory lost in 1940 fall within this category. Nevertheless, as these theorists might say, right reason suggests that after a very long time, seeking to recover lost property would no longer constitute an authentic just cause.

[14] Of course, it should go without saying that the simple existence of a prior wrong does not by itself make war lawful. The Natural Law theorists were quite clear that the wrong committed must be so serious that war is a proportionate response, that there was a genuine prospect for success, and that war was necessary to preserve the common good or to vindicate the rights of the aggrieved community.

[15] Francisco Suarez, On the Three Theological Virtues: Faith, Hope, and Charity (1621), “On Charity,” disputation XIII, section II, article 1. Gwladys L Williams, et al, trans, Selections from Three Works of Francisco Suarez, vol 2., p 805. Classics of International Law #20 (Oxford: Clarendon Press, 1944).

[16] Gentili was born in Italy but having Protestant sympathies fled to England in 1580, where he became Regius Professor of Law at Oxford.

[17] Alberico Gentili, Three Books on the Law of War (1612), book I, chapter 14. John C Rolfe, ed, De iure belli libri tres, vol 2, p 61. Classics of International Law #16 (repr., Buffalo, NY: William S Hein, 1995).

[18] Op cit, p 66.

[19] Hugo Grotius, The Rights of War and Peace, book II, chapter 1. Trans A C Campbell (New York: M Walter Dunne, 1901), p 76.

[20] Op cit, p 77.

[21] Suarez, op cit, section VI.

[22] I ask the reader’s indulgence in this section of the paper. I have quite deliberately not tried to provide citations and specific evidence for the comments I make here. While I think this might be done effectively, I also think it would tend to be distracting. Many people who are not professional philosophers or military officers accept the idea of a just war, even though they may not be familiar at all with the fine details of just war theory. Particularly in a democracy, however, their sense of what the theory requires can powerfully influence the choices of civilian and military leaders. To some degree, I am trying to capture here the sense that I think people have about a just war. I am painting with a wide brush and I invite readers to judge for themselves whether the brush strokes are accurate.

[23] Two essays that address this question over a thirty-year period are John Courtney Murray, “Morality and Modern War” (New York: The Council on Religion and International Affairs, 1959), and J Bryan Hehir, “Just War Theory in a Post-Cold War World,” The Journal of Religious Ethics 20 (1992) 237-257.

[24] Sometimes “defensive” is understood rather broadly to include actions that “defend” the common good or international peace. Thus even the First Gulf War of 1991 could be said to be defensive, though in the Natural Law tradition it would clearly not belong in that category.

[25] A sign of this is the recent public discussion concerning the interrogation of detainees and prisoners. Jus in bello criteria are rarely employed in the discussion, nor are terms defined and facts explored. Many people express outrage at the very idea of “torture,” though they are unclear about what constitutes torture and whether anything approximating torture has been employed. Others insist that we ought to do whatever is necessary to ensure our security.