Just and Unjust Wars

A Moral Argument with Historical Illustrations


By Michael Walzer

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“A classic in the field” (New York Times), this is a penetrating investigation into moral and ethical questions raised by war, drawing on examples from antiquity to the present.

Just and Unjust Wars has forever changed how we think about the ethics of conflict. In this modern classic, political philosopher Michael Walzer examines the moral issues that arise before, during, and after the wars we fight. Reaching from the Athenian attack on Melos, to the Mai Lai massacre, to the war in Afghanistan and beyond, Walzer mines historical and contemporary accounts and the testimony of participants, decision makers, and victims to explain when war is justified and what ethical limitations apply to those who wage it.





Against “Realism”

For as long as men and women have talked about war, they have talked about it in terms of right and wrong. And for almost as long, some among them have derided such talk, called it a charade, insisted that war lies beyond (or beneath) moral judgment. War is a world apart, where life itself is at stake, where human nature is reduced to its elemental forms, where self-interest and necessity prevail. Here men and women do what they must to save themselves and their communities, and morality and law have no place. Inter arma silent leges: in time of war the law is silent.

Sometimes this silence is extended to other forms of competitive activity, as in the popular proverb, “All’s fair in love and war.” That means that anything goes—any kind of deceit in love, any kind of violence in war. We can neither praise nor blame; there is nothing to say. And yet we are rarely silent. The language we use to talk about love and war is so rich with moral meaning that it could hardly have been developed except through centuries of argument. Faithfulness, devotion, chastity, shame, adultery, seduction, betrayal; aggression, self-defense, appeasement, cruelty, ruthlessness, atrocity, massacre—all these words are judgments, and judging is as common a human activity as loving or fighting.

It is true, however, that we often lack the courage of our judgments, and especially so in the case of military conflict. The moral posture of mankind is not well represented by that popular proverb about love and war. We would do better to mark a contrast rather than a similarity: before Venus, censorious; before Mars, timid. Not that we don’t justify or condemn particular attacks, but we do so hesitantly and uncertainly (or loudly and recklessly), as if we were not sure that our judgments reach to the reality of war.

The Realist Argument

Realism is the issue. The defenders of silent leges claim to have discovered an awful truth: what we conventionally call inhumanity is simply humanity under pressure. War strips away our civilized adornments and reveals our nakedness. They describe that nakedness for us, not without a certain relish: fearful, self-concerned, driven, murderous. They aren’t wrong in any simple sense. The words are sometimes descriptive. Paradoxically, the description is often a kind of apology: yes, our soldiers committed atrocities in the course of the battle, but that’s what war does to people, that’s what war is like. The proverb, all’s fair, is invoked in defense of conduct that appears to be unfair. And one urges silence on the law when one is engaged in activities that would otherwise be called unlawful. So there are arguments here that will enter into my own argument: justifications and excuses, references to necessity and duress, that we can recognize as forms of moral discourse and that have or don’t have force in particular cases. But there is also a general account of war as a realm of necessity and duress, the purpose of which is to make discourse about particular cases appear to be idle chatter, a mask of noise with which we conceal, even from ourselves, the awful truth. It is that general account that I have to challenge before I can begin my own work, and I want to challenge it at its source and in its most compelling form, as it is put forward by the historian Thucydides and the philosopher Thomas Hobbes. These two men, separated by 2,000 years, are collaborators of a kind, for Hobbes translated Thucydides’ History of the Peloponnesian War and then generalized its argument in his own Leviathan. It is not my purpose here to write a full philosophical response to Thucydides and Hobbes. I wish only to suggest, first by argument and then by example, that the judgment of war and of wartime conduct is a serious enterprise.

The Melian Dialogue

The dialogue between the Athenian generals Cleomedes and Tisias and the magistrates of the island state of Melos is one of the high points of Thucydides’ History and the climax of his realism. Melos was a Spartan colony, and its people had “therefore refused to be subject, as the rest of the islands were, unto the Athenians; but rested at first neutral; and afterwards, when the Athenians put them to it by wasting of their lands, they entered into open war.”1 This is a classic account of aggression, for to commit aggression is simply to “put people to it” as Thucydides describes. But such a description, he seems to say, is merely external; he wants to show us the inner meaning of war. His spokesmen are the two Athenian generals, who demand a parley and then speak as generals have rarely done in military history. Let us have no fine words about justice, they say. We for our part will not pretend that, having defeated the Persians, our empire is deserved; you must not claim that having done no injury to the Athenian people, you have a right to be let alone. We will talk instead of what is feasible and what is necessary. For this is what war is really like: “they that have odds of power exact as much as they can, and the weak yield to such conditions as they can get.”

It is not only the Melians here who bear the burdens of necessity. The Athenians are driven, too; they must expand their empire, Cleomedes and Tisias believe, or lose what they already have. The neutrality of Melos “will be an argument of our weakness, and your hatred of our power, among those we have rule over.” It will inspire rebellion throughout the islands, wherever men and women are “offended with the necessity of subjection”—and what subject is not offended, eager for freedom, resentful of his conquerors? When the Athenian generals say that men “will everywhere reign over such as they be too strong for,” they are not only describing the desire for glory and command, but also the more narrow necessity of inter-state politics: reign or be subject. If they do not conquer when they can, they only reveal weakness and invite attack; and so, “by a necessity of nature” (a phrase Hobbes later made his own), they conquer when they can.

The Melians, on the other hand, are too weak to conquer. They face a harsher necessity: yield or be destroyed. “For you have not in hand a match of valor upon equal terms . . . but rather a consultation upon your safety . . .” The rulers of Melos, however, value freedom above safety: “If you then to retain your command, and your vassals to get loose from you, will undergo the utmost danger: would it not in us, that be already free, be great baseness and cowardice, if we should not encounter anything whatsoever rather than suffer ourselves to be brought into bondage?” Though they know that it will be a “hard matter” to stand against the power and fortune of Athens, “nevertheless we believe that, for fortune, we shall be nothing inferior, as having the gods on our side, because we stand innocent against men unjust.” And as for power, they hope for assistance from the Spartans, “who are of necessity obliged, if for no other cause, yet for consanguinity’s sake and for their own honor to defend us.” But the gods, too, reign where they can, reply the Athenian generals, and consanguinity and honor have nothing to do with necessity. The Spartans will (necessarily) think only of themselves: “most apparently of all men, they hold for honorable that which pleaseth and for just that which profiteth.”

So the argument ended. The magistrates refused to surrender; the Athenians laid siege to their city; the Spartans sent no help. Finally, after some months of fighting, in the winter of 416 B.C., Melos was betrayed by several of its citizens. When further resistance seemed impossible, the Melians “yielded themselves to the discretion of the Athenians: who slew all the men of military age, made slaves of the women and children; and inhabited the place with a colony sent thither afterwards of 500 men of their own.”

The dialogue between the generals and the magistrates is a literary and philosophical construction of Thucydides. The magistrates speak as they well might have done, but their conventional piety and heroism is only a foil to what the classical critic Dionysius calls the “depraved shrewdness” of the Athenian generals.2 It is the generals who have often seemed unbelievable. Their words, writes Dionysius, “were appropriate to oriental monarchs . . . but unfit to be spoken by Athenians . . .”* Perhaps Thucydides means us to notice the unfitness, not so much of the words but of the policies they were used to defend, and thinks we might have missed it had he permitted the generals to speak as they probably in fact spoke, weaving “fair pretenses” over their vile actions. We are to understand that Athens is no longer itself. Cleomedes and Tisias do not represent that noble people who fought the Persians in the name of freedom and whose politics and culture, as Dionysius says, “exercised such a humanizing influence on everyday life.” They represent instead the imperial decadence of the city state. It is not that they are war criminals in the modern sense; that idea is alien to Thucydides. But they embody a certain loss of ethical balance, of restraint and moderation. Their statesmanship is flawed, and their “realistic” speeches provide an ironic contrast to the blindness and arrogance with which the Athenians only a few months later launched the disastrous expedition to Sicily. The History, on this view, is a tragedy and Athens itself the tragic hero.3 Thucydides has given us a morality play in the Greek style. We can glimpse his meaning in Euripides’ The Trojan Women, written in the immediate aftermath of the conquest of Melos and undoubtedly intended to suggest the human significance of slaughter and slavery—and to predict a divine retribution:4

                How ye are blind

             Ye treaders down of cities, ye that cast

             Temples to desolation, and lay waste

             Tombs, the untrodden sanctuaries where lie

             The ancient dead; yourselves so soon to die!

But Thucydides seems in fact to be making a rather different, and a more secular, statement than this quotation suggests, and not about Athens so much as about war itself. He probably did not mean the harshness of the Athenian generals to be taken as a sign of depravity, but rather as a sign of impatience, toughmindedness, honesty—qualities of mind not inappropriate in miltary commanders. He is arguing, as Werner Jaeger has said, that “the principle of force forms a realm of its own, with laws of its own,” distinct and separate from the laws of moral life.5 This is certainly the way Hobbes read Thucydides, and it is the reading with which we must come to grips. For if the realm of force is indeed distinct and if this is an accurate account of its laws, then one could no more criticize the Athenians for their wartime policies than one could criticize a stone for falling downwards. The slaughter of the Melians is explained by reference to the circumstances of war and the necessities of nature; and again, there is nothing to say. Or rather, one can say anything, call necessity cruel and war hellish; but while these statements may be true in their own terms, they do not touch the political realities of the case or help us understand the Athenian decision.

It is important to stress, however, that Thucydides has told us nothing at all about the Athenian decision. And if we place ourselves, not in the council room at Melos where a cruel policy was being expounded, but in the assembly at Athens where that policy was first adopted, the argument of the generals has a very different ring. In the Greek as in the English language, the word necessity “doubles the parts of indispensable and inevitable.”6 At Melos, Cleomedes and Tisias mixed the two of these, stressing the last. In the assembly they could have argued only about the first, claiming, I suppose, that the destruction of Melos was necessary (indispensable) for the preservation of the empire. But this claim is rhetorical in two senses. First, it evades the moral question of whether the preservation of the empire was itself necessary. There were some Athenians, at least, who had doubts about that, and more who doubted that the empire had to be a uniform system of domination and subjection (as the policy adopted for Melos suggested). Secondly, it exaggerates the knowledge and foresight of the generals. They are not saying with certainty that Athens will fall unless Melos is destroyed; their argument has to do with probabilities and risks. And such arguments are always arguable. Would the destruction of Melos really reduce Athenian risks? Are there alternative policies? What are the likely costs of this one? Would it be right? What would other people think of Athens if it were carried out?

Once the debate begins, all sorts of moral and strategic questions are likely to come up. And for the participants in the debate, the outcome is not going to be determined “by a necessity of nature,” but by the opinions they hold or come to hold as a result of the arguments they hear and then by the decisions they freely make, individually and collectively. Afterwards, the generals claim that a certain decision was inevitable; and that, presumably, is what Thucydides wants us to believe. But the claim can only be made afterwards, for inevitability here is mediated by a process of political deliberation, and Thucydides could not know what was inevitable until that process had been completed. Judgments of necessity in this sense are always retrospective in character—the work of historians, not historical actors.

Now, the moral point of view derives its legitimacy from the perspective of the actor. When we make moral judgments, we try to recapture that perspective. We reiterate the decision-making process, or we rehearse our own future decisions, asking what we would have done (or what we would do) in similar circumstances. The Athenian generals recognize the importance of such questions, for they defend their policy certain “that you likewise, and others that should have the same power which we have, would do the same.” But that is a dubious knowledge, especially so once we realize that the “Melian decree” was sharply opposed in the Athenian assembly. Our standpoint is that of citizens debating the decree. What should we do?

We have no account of the Athenian decision to attack Melos or of the decision (which may have been taken at the same time) to kill and enslave its people. Plutarch claims that it was Alcibiades, chief architect of the Sicilian expedition, who was “the principal cause of the slaughter . . . having spoken in favor of the decree.”7 He played the part of Cleon in the debate that Thucydides does record, that occured some years earlier, over the fate of Mytilene. It is worth glancing back at that earlier argument. Mytilene had been an ally of Athens from the time of the Persian War; it was never a subject city in any formal way, but bound by treaty to the Athenian cause. In 428, it rebelled and formed an alliance with the Spartans. After considerable fighting, the city was captured by Athenian forces, and the assembly determined “to put to death . . . all the men of Mytilene that were of age, and to make slaves of the women and children: laying to their charge the revolt itself, in that they revolted not being in subjection as others were . . .”8 But the following day the citizens “felt a kind of repentance . . . and began to consider what a great and cruel decree it was, that not the authors only, but that the whole city should be destroyed.” It is this second debate that Thucydides has recorded, or some part of it, giving us two speeches, that of Cleon upholding the original decree and that of Diodotus urging its revocation. Cleon argues largely in terms of collective guilt and retributive justice; Diodotus offers a critique of the deterrent effects of capital punishment. The assembly accepts Diodotus’ position, convinced apparently that the destruction of Mytilene would not uphold the force of treaties or ensure the stability of the empire. It is the appeal to interest that triumphs—as has often been pointed out—though it should be remembered that the occasion for the appeal was the repentance of the citizens. Moral anxiety, not political calculation, leads them to worry about the effectiveness of their decree.

In the debate over Melos, the positions must have been reversed. Now there was no retributivist argument to make, for the Melians had done Athens no injury. Alcibiades probably talked like Thucydides’ generals, though with the all-important difference I have already noted. When he told his fellow citizens that the decree was necessary, he didn’t mean that it was ordained by the laws that govern the realm of force; he meant merely that it was needed (in his view) to reduce the risks of rebellion among the subject cities of the Athenian empire. And his opponents probably argued, like the Melians, that the decree was dishonorable and unjust and would more likely excite resentment than fear throughout the islands, that Melos did not threaten Athens in any way, and that other policies would serve Athenian interests and Athenian self-esteem. Perhaps they also reminded the citizens of their repentance in the case of Mytilene and urged them once again to avoid the cruelty of massacre and enslavement. How Alcibiades won out, and how close the vote was, we don’t know. But there is no reason to think that the decision was predetermined and debate of no avail: no more with Melos than with Mytilene. Stand in imagination in the Athenian assembly, and one can still feel a sense of freedom.

But the realism of the Athenian generals has a further thrust. It is not only a denial of the freedom that makes moral decision possible; it is a denial also of the meaningfulness of moral argument. The second claim is closely related to the first. If we must act in accordance with our interests, driven by our fears of one another, then talk about justice cannot possibly be anything more than talk. It refers to no purposes that we can make our own and to no goals that we can share with others. That is why the Athenian generals could have woven “fair pretenses” as easily as the Melian magistrates; in discourse of this sort anything can be said. The words have no clear references, no certain definitions, no logical entailments. They are, as Hobbes writes in Leviathan, “ever used with relation to the person that useth them,” and they express that person’s appetites and fears and nothing else. It is only “most apparent” in the Spartans, but true for everyone, that “they hold for honorable that which pleaseth them and for just that which profiteth.” Or, as Hobbes later explained, the names of the virtues and vices are of “uncertain signification.”9

For one calleth wisdom, what another calleth fear; and one cruelty what another justice; one prodigality, what another magnanimity . . . etc. And therefore such names can never be true grounds of any ratiocination.

“Never”—until the sovereign, who is also the supreme linguistic authority, fixes the meaning of the moral vocabulary; but in the state of war, “never” without qualification, because in that state, by definition, no sovereign rules. In fact, even in civil society, the sovereign does not entirely succeed in bringing certainty into the world of virtue and vice. Hence moral discourse is always suspect, and war is only an extreme case of the anarchy of moral meanings. It is generally true, but especially so in time of violent conflict, that we can understand what other people are saying only if we see through their “fair pretenses” and translate moral talk into the harder currency of interest talk. When the Melians insist that their cause is just, they are saying only that they don’t want to be subject; and had the generals claimed that Athens deserved its empire, they would simply have been expressing the lust for conquest or the fear of overthrow.

This is a powerful argument because it plays upon the common experience of moral disagreement—painful, sustained, exasperating, and endless. For all its realism, however, it fails to get at the realities of that experience or to explain its character. We can see this clearly, I think, if we look again at the argument over the Mytilene decree. Hobbes may well have had this debate in mind when he wrote, “and one [calleth] cruelty what another justice . . .” The Athenians repented of their cruelty, writes Thucydides, while Cleon told them that they had not been cruel at all but justly severe. Yet this was in no sense a disagreement over the meaning of words. Had there been no common meanings, there could have been no debate at all. The cruelty of the Athenians consisted in seeking to punish not only the authors of the rebellion but others as well, and Cleon agreed that that would indeed be cruel. He then went on to argue, as he had to do given his position, that in Mytilene there were no “others.” “Let not the fault be laid upon a few, and the people absolved. For they have all alike taken arms against us . . .”

I cannot pursue the argument further, since Thucydides doesn’t, but there is an obvious rejoinder to Cleon, having to do with the status of the women and children of Mytilene. This might involve the deployment of additional moral terms (innocence, for example); but it would not hang—any more than the argument about cruelty and justice hangs—on idiosyncratic definitions. In fact, definitions are not at issue here, but descriptions and interpretations. The Athenians shared a moral vocabulary, shared it with the people of Mytilene and Melos; and allowing for cultural differences, they share it with us too. They had no difficulty, and we have none, in understanding the claim of the Melian magistrates that the invasion of their island was unjust. It is in applying the agreed-upon words to actual cases that we come to disagree. These disagreements are in part generated and always compounded by antagonistic interests and mutual fears. But they have other causes, too, which help to explain the complex and disparate ways in which men and women (even when they have similar interests and no reason to fear one another) position themselves in the moral world. There are, first of all, serious difficulties of perception and information (in war and politics generally), and so controversies arise over “the facts of the case.” There are sharp disparities in the weight we attach even to values we share, as there are in the actions we are ready to condone when these values are threatened. There are conflicting commitments and obligations that force us into violent antagonism even when we see the point of one another’s positions. All this is real enough, and common enough: it makes morality into a world of good-faith quarrels as well as a world of ideology and verbal manipulation.

In any case, the possibilities for manipulation are limited. Whether or not people speak in good faith, they cannot say just anything they please. Moral talk is coercive; one thing leads to another. Perhaps that’s why the Athenian generals did not want to begin. A war called unjust is not, to paraphrase Hobbes, a war misliked; it is a war misliked for particular reasons, and anyone making the charge is required to provide particular sorts of evidence. Similarly, if I claim that I am fighting justly, I must also claim that I was attacked (“put to it,” as the Melians were), or threatened with attack, or that I am coming to the aid of a victim of someone else’s attack. And each of these claims has its own entailments, leading me deeper and deeper into a world of discourse where, though I can go on talking indefinitely, I am severely constrained in what I can say. I must say this or that, and at many points in a long argument this or that will be true or false. We don’t have to translate moral talk into interest talk in order to understand it; morality refers in its own way to the real world.

Let us consider a Hobbist example. In Chapter XXI of Leviathan, Hobbes urges that we make allowance for the “natural timorousness” of mankind. “When armies fight, there is on one side, or both a running away; yet when they do it not out of treachery, but fear, they are not esteemed to do it unjustly, but dishonorably.” Now, judgments are called for here: we are to distinguish cowards from traitors. If these are words of “inconstant signification,” the task is impossible and absurd. Every traitor would plead natural timorousness, and we would accept the plea or not depending on whether the soldier was a friend or an enemy, an obstacle to our advancement or an ally and supporter. I suppose we sometimes do behave that way, but it is not the case (nor does Hobbes, when it comes to cases, suppose that it is) that the judgments we make can only be understood in these terms. When we charge a man with treason, we have to tell a very special kind of story about him, and we have to provide concrete evidence that the story is true. If we call him a traitor when we cannot tell that story, we are not using words inconstantly, we are simply lying.

Strategy and Morality

Morality and justice are talked about in much the same way as military strategy. Strategy is the other language of war, and while it is commonly said to be free from the difficulties of moral discourse, its use is equally problematic. Though generals agree on the meaning of strategic terms—entrapment, retreat, flanking maneuver, concentration of forces, and so on—they nevertheless disagree about strategically appropriate courses of action. They argue about what ought to be done. After the battle, they disagree about what happened, and if they were defeated, they argue about who was to blame. Strategy, like morality, is a language of justification.* Every confused and cowardly commander describes his hesitations and panics as part of an elaborate plan; the strategic vocabulary is as available to him as it is to a competent commander. But that is not to say that its terms are meaningless. It would be a great triumph for the incompetent if they were, for we would then have no way to talk about incompetence. No doubt, “one calleth retreat what another calleth strategic redeployment . . .” But we do know the difference between these two, and though the facts of the case may be difficult to collect and interpret, we are nevertheless able to make critical judgments.


  • "A magnificent book, an honor to its writer...a book that makes for a return of civilized discussion of the question of the morality of war."—New York Review of Books
  • "A passionate defense of the old principle of non-combatant immunity.... [Walzer] is both thorough and persuasive in his exploration of a very intricate subject."—Washington Post
  • "A classic in the field."—New York Times
  • "One of the most significant modern restatements of just-war thinking."—Nation
  • "A clear, humane, and startingly original survey of the moral issues that complicate modern war-making."—Atlantic

On Sale
Aug 11, 2015
Page Count
416 pages
Basic Books

Michael Walzer

About the Author

Michael Walzer is professor emeritus of social science at the Institute for Advanced Study, Princeton, NJ, and the author of many widely heralded books, including Spheres of Injustice, Exodus and Revolution, and The Company of Critics.

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