Australian troops returning to the No 9 Squadron, RAAF, Iroquois helicopter A2-1024 after completing a sweep of the island where Viet Cong (VC) had been spotted 1966

Australian soldiers boarding a No 9 Squadron RAAF helicopter during Operation Hayman, Vung Tau Special Zone, Vietnam, (1966) | Gerald Wallace Westbury / Public domain

The following is an excerpt from an essay first published in Social Research: An International Quarterly in the Winter, 2002 issue, and reprinted in the journal’s Spring 2024 anniversary issue, Social Research at 90.

Some political theories die and go to heaven; some, I hope, die and go to hell. But some have a long life in this world, a history most often of service to the powers that be, but also, sometimes, an oppositionist history. The theory of just war began in the service of the powers. At least that is how I interpret Augustine’s achievement: he replaced the radical refusal of Christian pacifists with the active ministry of the Christian soldier. Now pious Christians could fight on behalf of the worldly city, for the sake of imperial peace (in this case, literally, pax Romana); but they had to fight justly, only for the sake of peace, and always, Augustine insisted, with a downcast demeanor, without anger or lust. Seen from the perspective of primitive Christianity, this account of just war was simply an excuse, a way of making war morally and religiously possible. And that was indeed the function of the theory. But its defenders would have said, and I am inclined to agree, that it made war possible in a world where war was, sometimes, necessary.

From the beginning, the theory had a critical edge: soldiers (or, at least, their officers) were supposed to refuse to fight in wars of conquest and to oppose or abstain from the standard military practices of rape and pillage after the battle was won. But just war was a worldly theory, in every sense of that term, and it continued to serve worldly interests against Christian radicalism. It is important to note, though, that Christian radicalism had more than one version: it could be expressed in a pacifist rejection of war, but it could also be expressed in war itself, in the religiously driven crusade. Augustine opposed the first of these; the medieval scholastics, following in Aquinas’s footsteps, set themselves against the second. The classic statement is Vitoria’s: “Difference of religion cannot be a cause of just war.” For centuries, from the time of the Crusades to the religious wars of the Reformation years, many of the priests and preachers of Christian Europe, many lords and barons (and even a few kings) had been committed to the legitimacy of using military force against unbelievers: they had their own version of jihad. Vitoria claimed, by contrast, that “the sole and only just cause for waging war is when harm has been inflicted.” Just war was an argument of the religious center against pacifists, on the one side, and holy warriors, on the other, and because of its enemies (and even though its proponents were theologians), it took shape as a secular theory—which is simply another way of describing its worldliness.

So the rulers of this world embraced the theory and did not fight a single war without describing it, or hiring intellectuals to describe it, as a war for peace and justice. Most often, of course, this description was hypocritical: the tribute that vice pays to virtue. But the need to pay the tribute opens those who pay it to the criticism of the virtuous—that is, of the brave and virtuous, of whom there have been only a few (but one could also say: at least a few). I will cite one heroic moment, from the history of the academic world: sometime around 1520, the faculty of the University of Salamanca met in solemn assembly and voted that the Spanish conquest of Central America was a violation of natural law and an unjust war. I have not been able to learn anything about the subsequent fate of the good professors. Certainly, there were not many moments like that one, but what happened at Salamanca suggests that just war never lost its critical edge. The theory provided worldly reasons for going to war, but the reasons were limited—and they had to be worldly. Converting the Aztecs to Christianity was not a just cause, nor was seizing the gold of the Americas or enslaving its inhabitants.

Writers like Grotius and Pufendorf incorporated just war theory into international law, but the rise of the modern state and the legal (and philosophical) acceptance of state sovereignty pushed the theory into the background. Now the political foreground was occupied by people we can think of as Machiavellian princes, hard men (and sometimes women), driven by “reason of state,” who did what (they said) they had to do. Worldly prudence triumphed over worldly justice, realism over what was increasingly disparaged as naive idealism. The princes of the world continued to defend their wars, using the language of international law, which was also, at least in part, the language of just war. But the defenses were marginal to the enterprise, and I suspect that it was the least important of the state’s intellectuals who put them forward. States claimed a right to fight whenever their rulers deemed it necessary, and the rulers took sovereignty to mean that no one could judge their decisions. They not only fought when they wanted; they fought how they wanted, returning to the old Roman maxim that held war to be a lawless activity: inter arma silent leges—which, again, was taken to mean that there was no law above or beyond the decrees of the state; conventional restraints on the conduct of war could always be overridden for the sake of victory. Arguments about justice were treated as a kind of moralizing, inappropriate to the anarchic conditions of international society. For this world, just war was not worldly enough.

In the 1950s and early 1960s, when I was in graduate school, realism was the reigning doctrine in the field of “international relations.” The standard reference was not to justice but to interest. Moral argument was against the rules of the discipline as it was commonly practiced, although a few writers defended interest as the new morality. There were many political scientists in those years who preened themselves as modern Machiavellis and dreamed of whispering in the ear of the prince, and a certain number of them, enough to stimulate the ambition of the others, actually got to whisper. They practiced being cool and tough-minded; they taught the princes, who did not always need to be taught, how to get results through the calculated application of force. Results were understood in terms of “the national interest,” which was the objectively determined sum of power and wealth here and now plus the probability of future power and wealth. More of both was almost always taken to be better; only a few writers argued for the acceptance of prudential limits; moral limits were, as I remember those years, never discussed. Just war theory was relegated to religion departments, theological seminaries, and a few Catholic universities. And even in those places, isolated as they were from the political world, the theory was pressed toward realist positions; perhaps for the sake of self-preservation, its advocates surrendered something of its critical edge.

Vietnam changed all this, although it took a while for the change to register at the theoretical level. What happened first occurred in the realm of practice. The war became a subject of political debate; it was widely opposed, mostly by people on the left. These were people heavily influenced by Marxism; they also spoke a language of interest; they shared with the princes and professors of American politics a disdain for moralizing. And yet the experience of the war pressed them toward moral argument. Of course, the war in their eyes was radically imprudent; it could not be won; its costs, even if Americans thought only of themselves, were much too high; it was an imperialist adventure unwise even for the imperialists; it set the United States against the cause of national liberation, which would alienate it from the Third World (and significant parts of the First). But these claims failed utterly to express the feelings of most of the war’s opponents, feelings that had to do with the systematic exposure of Vietnamese civilians to the violence of American war-making. Almost against its will, the left fell into morality. All of us in the antiwar camp suddenly began talking the language of just war—though we did not know that that was what we were doing.

It may seem odd to recall the 60s in this way, since today the left seems all too quick to make moral arguments, even absolutist moral arguments. But this description of the contemporary left seems to me mistaken. A certain kind of politicized, instrumental, and highly selective moralizing is indeed increasingly common among leftist writers, but this is not serious moral argument. It is not what we learned, or ought to have learned, from the Vietnam years. What happened then was that people on the left, and many others too, looked for a common moral language. And what was most available was the language of just war. We were, all of us, a bit rusty, unaccustomed to speaking in public about morality. The realist ascendancy had robbed us of the very words that we needed, which we slowly reclaimed: aggression, intervention, just cause, self-defense, noncombatant immunity, proportionality, prisoners of war, civilians, double effect, terrorism, war crimes. And we came to understand that these words had meanings. Of course, they could be used instrumentally; that is always true of political and moral terms. But if we attended to their meanings, we found ourselves involved in a discussion that had its own structure. Like characters in a novel, concepts in a theory shape the narrative or the argument in which they figure.