The Just War Tradition

The Episcopal Church calls upon all of its members to study, understand and utilize the Just War tradition developed over the centuries (General Convention resolutions 2003-A033 and 2003-A132).  The following is an overview of the Just War tradition written with the Church’s military chaplains in mind, and intended to assist them in their ministry to those who serve or have served in the armed forces.  It was prepared by Marc Livecche, Ph.D., the McDonald Distinguished Scholar of Ethics, War, and Public Life at “Providence: A Journal of Christianity & American Foreign Policy,” with editorial assistance from Matt Gobush, member of the Church’s Standing Commission on World Mission, for the Military Chaplains Just War Education Project, supported by the Constable Trust.

Historical Overview

To talk about the just war tradition can be misleading because there are in fact, several – sometimes competing – versions.  Within the last fifty years, for example, bishops in the Roman Catholic Church have interpreted the tradition in novel ways to impute a presumption against the use of force and locate legitimate authority exclusively in the United Nations, for example.  Nevertheless, Christian thinkers, particularly but not exclusively, often have in view what can be called the classical just war tradition, compromised of both jus ad bellum criteria governing the decision to go to war, and jus in bellow criteria regarding conduct in war.  The classical tradition has served as the basis for discussions within the Episcopal Church.  

While the classical just war tradition as we now know it took recognizable shape only in the Middle Ages, its foundational assumptions and ideas can be traced back to ancient Israel and the classical Greek and Roman worlds. This ancient pedigree would find its early Christian expression in the 4th century theologians Ambrose and, most especially, in his pupil Augustine. 

Augustine saw no necessary contradiction between a Christian engaging in warfare and loving the enemy. He insisted that, like a parent who disciplines a recalcitrant child with a “benevolent harshness,” one can punish an enemy while having the enemy’s good in mind (Augustine, 2001). In this way, Augustine proclaimed a vision of war that was a manifestation, rather than a contradiction, of love. This early Augustinian establishment of just war’s foundations proceeded apace with his maturing theory of politics first outlined in The City of God, which characterized the good society as one embodying a just order and, therefore, enjoying peaceful relations—both internally among its own people and externally with similarly fashioned societies (Augustine, 2003). Important though it was, however, Augustine’s just war thought was scattered through a number of works whose primary focus lay elsewhere. The forging of a systematic, consolidated conception of just war would be the achievement of a later era (Johnson, 2005a).

Beginning around the middle of the 12th century, a more coherent framework began to emerge with the Decretum, by the Bolognese canon lawyer, Gratian. This systematization took theological form in Thomas Aquinas (ca. 1125-1274). Significantly, Thomas followed Augustine’s emphasis on love by placing his own discussion of just war in the Summa Theologica in the midst of his treatment of caritas or charity (Aquanis). Later in the Middle Ages, particularly during the Hundred Years War, this “canonical and theological conception of just war was further elaborated by incorporation of ideas, customs, and practices from the chivalric code and the experience of war” (Johnson, 2005b). 

During the Reformation, Martin Luther (1483-1546) departed from certain traditional tenets of the just war tradition, even as he improved the tradition in other ways. Ever the bombastic iconoclast, Luther tended “to dispense with traditional subtleties and distinctions” thereby giving an account of war with considerably less nuance than earlier writers (Corey and Charles, 2014). Most pointedly, Luther’s treatment of right intention lacks any reference to love for the enemy and one finds few restrictions in his discussion of the ethics of how one actually fights once conflict is engaged. John Calvin (1509-1564) marked a substantive return to earlier emphases, illustrated by his grounding of the coercive powers of the state in natural law, thereby linking civil and moral law in the pursuit of justice (Calvin, 1960). This gestures again to Augustine’s distinction between internal dispositions and external acts, resulting in our ability to both love and kill the enemy (Calvin, 1960) as we distinguish between the sinner and the sin (Calvin, 1973).

The primarily Christian theological content of just war tradition had begun to wane by the 17th century. While early-modern just war thinkers like the Spanish neo-scholastics Francisco de Vitoria (1492-1546) and Francisco Suárez (1548-1617) and the Dutch jurist Hugo Grotius (1583-1645) were theologians who used Christian scripture, texts, and arguments, they each also attempted to present just war principles on the more universal ground of natural law. In doing so, they developed arguments both more comprehensive as well as more widely applicable beyond the Christian West. Grotius, in particular, also contributed significantly to the deeper development of criteria regarding the moral conduct of war.

In the 1960s, however, Paul Ramsey (1913-88) pioneered a revival of specifically Christian, Augustinian just war thinking, which has been kept alive since in the work of Jean Bethke Elshtain (1941-2013), Oliver O’Donovan (1945- ), (Nigel Biggar (1955- ), Eric Patterson (1971-), Marc LiVecche (1972-), and others.

Over the millennia, the just war tradition has developed two sets of criteria, one pertaining to the justice of going to war in the first place (jus ad bellum) and the other regarding justice in the course of fighting (jus in bello).  The Episcopal Church has embraced these criteria as means to understanding and applying the tradition (General Convention resolution 2003-033).  While the jus ad bellum criteria are particularly useful to policymakers, civilian leaders and citizens in deliberations about war, many military chaplains have found the jus in bellow criteria more relevant to their direct ministry to servicemembers and veterans.  For this reason, the following overview reverses the typical order to present the jus in bello criteria first.  

Jus in Bello 

In its study of the classic Just War tradition, the Episcopal Church has cited two criteria for discerning the justice of conduct in a war: proportionality and discrimination (General Convention resolution 2003-A033).  Both are discussed below.  In addition, the criterion of military necessity is offered, which is implied in the tradition but warrants explicit elaboration, as many contemporary Just War scholars have argued.

Proportionality

In everyday parlance, for something to be said to be proportional it must correspond in size or amount in relationship to something else. In thinking about war, the principle of proportionality has suffered under this like-for-like presumption and has often resulted in confused moral reasoning. The problem begins with the lack of agreement as to what proportionality actually means. One claim, taking its cue from the common usage, suggests proportionality requires opposing force with similar force. This, as Jim Johnson quips, is to make war akin to a football game (Johnson, 2005a)

Better is the suggestion that proportionality calls for ensuring that only the minimum amount of force is used to achieve the objective and to avoid harming noncombatants. There are two immediate problems with this. First, in practice, it tends to issue in the assumption that any action entailing great destructive power is inherently disproportionate. Second, it is simply a mistake to conceive of proportionality’s primary imperative as restraint.

It is true that a number of international agreements as well as customary international law points both to using only that amount of force as is proportionate to the injury received and only as much as required to reinstate the status quo ante. And it’s also true that combatants are required to employ only as much force as is necessary to achieve legitimate military objectives and as is proportionate to the importance of those objectives. The just warrior must be neither gratuitous nor excessive. But casting the doctrine of proportionality in this way both demands something that is probably impossible to deliver as well as omits something that is essential to obtain.

The requirement to employ “no more force than necessary” will in many cases—especially in the time-constrained high-stakes context of battle—be impossible to determine. It’s right that one should attempt to limit violence to only what is deemed necessary, but it is also true that when trying to make this determination our sense of proportionality should be leavened by the commitment to decisiveness stressed above and, with it, that preference for hedging against falling short, even as we limit this by considerations of discrimination and proportion. 

If the basic imperative of proportionality is not restraint, what is it? Classically understood, proportionality has at its core the requirement to calculate gains and losses. Proportionality is about determining when a particular use of force—whether a weapon or a tactic—is likely to produce more harm than good. This is done by focusing on the aim of restoring a justly ordered peace and considering the measure of good intended to be achieved against two measures of harm: that which will likely occur if a particular act of force is used, and that which will likely be done if such force is not used. The operational interpretation of this would include targeting for air strikes in an effort to maximize good results—defeating the enemy, shortening the conflict, force protection—over negative results—non-combatant harm, unnecessary destruction, etc.

Discrimination

The moral reasoning associated with the principle of discrimination, or civilian or noncombatant immunity, is well contested. Not the least contentious issue, as scholar A.J. Coates reminds us, has to do with the moral status on which the principle rests. “Traditionally,” he writes, “distinction is seen to arise out of the moral prohibition on the taking of innocent life” (Coates, 1997). The hang up is on precisely what constitutes innocence. 

Because so much of what delineates between guilt and innocence has to do with the interior moral state, assessment quickly becomes difficult, so much so that the personal guilt or innocence of those whom they subject to attack is essentially impossible for a warfighter to determine. In practice, therefore, the principle has come to be understood in a non-subjective moral sense. Coates writes:

The logic of just war theorizing points to such an understanding of “innocence,” since the use of force in the first instance is seen to be justified only in response to an attack or threatened attack. In line with its etymological derivation from the Latin nocere (“to harm”), “innocent” in this context means “harmless” rather than “blameless.” 

This emphasis links us to the notion of “forfeiture,” which states that one has rendered themselves liable to harm on account of the threat they pose. One is not liable to harm when they do not pose, or no longer pose, harm to others. The operative moral term, then, is noncombatant, as opposed to combatant, both of which follows from direct involvement in prosecuting the war. Those rather easily classified as noncombatant include the very young, the very old, the infirm, and all those who lack the capacity or will to engage in fighting, including surrendered troops (Coates, 1997). 

Not directly and intentionally harming noncombatants is in most instances defined as an exceptionless moral rule. Nevertheless, the ambiguity surrounding who is or is not a noncombatant, amplified by the confusion as to what helping to prosecute a war really means, and what exactly is meant by “intentional harm” has led to continued debate. Mechanisms such as the doctrine of double effect—which allows unintentional harm to noncombatants—have been applied to aid moral deliberation; although these additional tools too have themselves become focal points of intense argument. 

The Swiss international lawyer, Emer de Vattel (1714-1767), has had a lasting influence on just war thinking. In particular, his The Law of Nations has especially helped shape international law. Grounding many of Vattel’s keen observations is his concern regarding the tension between necessity—doing what is required to achieve the war aim—and deference to the humanity of the enemy. His assertion of the former permits a broad assortment of actions and admits of occasional exceptions to sometimes commonly accepted restraints. 

For instance, the doctrine of discrimination includes not only respecting the lives of noncombatants, but also observing restraints against destroying infrastructure essential to maintaining human welfare. Nevertheless, it may be that extreme necessity—often because of nefarious enemy tactics—requires destroying things—temples, tombs, public buildings and works—that normally ought to be spared (Vattel, 2008). In other cases, it may be even surrendered enemy fighters ought not to be spared:

There is, however, one case, in which we may refuse to spare the life on an enemy who surrenders, or to allow any capitulation to a town reduced to the last extremity. It is when that enemy has been guilty of some enormous breach of the law of nations, and particularly when he has violated the laws of war (Vattel, 2008).

Nevertheless, in the main, it is essential to Vattel that the common humanity even one’s enemy is recognized. 

Let us not forget that our enemies are men. Though reduced to the disagreeable necessity of prosecuting our right by force of arms, let us not divest ourselves that charity which connects us with all mankind. Thus we shall courageously defend our country’s right without violating those of human nature. Let our valour preserve itself from every stain of cruelty, and the lustre of victory will not be tarnished by inhuman and brutal actions (Vattel, 2008).

In everything above, it should be clear that whatever the morality of war, warfare remains a terrible thing. Indeed, it is so terrible—in terms of both loss of lives and sheer destruction—that many within the Christian tradition have believed that war—no matter the justifying reasons—remains utterly unreasonable and must never be waged.

Military Necessity

The principle of military necessity is well-understood in the manuals of modern militaries and is recognized in the war convention. In the U.S. and UK, military personnel go through a law of armed conflict (LOAC) refresher training annually on the in bello principles, starting with military necessity. Only then do they go on to discuss proportionality and non-combatant immunity, or distinction. When foreign militaries, particularly in developing countries, receive training from the United States, other Western militaries, or the excellent curriculum from the International Committee of the Red Cross, they receive a similar experience, which emphasizes military necessity alongside proportionality, non-combatant immunity, unnecessary suffering (the principle of humanity), prohibited arms, and the like. Moreover, the legal textbooks at every major law school emphasize military necessity.[1]  

However, traditional just war theorists have failed to list the concept alongside the jus in bello principles of proportionality and distinction. This failure is a significant loss. A strong argument, based on biblical conceptions of stewardship among much else, could be made to reinsert military necessity into classical just war morality.

What is military necessity? The Lieber Code, issued under President Lincoln as General Order 100, defined military necessity in Article 14 as the “measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war” (Hartigan, 1983). The U.S. Department of Defence Law of War Manual says that military necessity may be defined as “the principle that justifies the use of all measures needed to defeat the enemy as quickly and efficiently as possible that are not prohibited by the law of war” (U.S. Department of Defense, 2016).  Gary D. Solis in his legal textbook, The Law of Armed Conflict, writes, “military necessity is an attempt to realize the purpose of armed conflict, gaining military advantage while minimizing human suffering and physical destruction” (Solis, 2010).  Finally, William V. O’Brien, in his classic text, writes, 

Legitimate military necessity consists in all measures immediately indispensable and proportionate to a legitimate military end, provided that they are not prohibited by the laws of war or the natural law, when taken on the decision of a responsible commander, subject to review (O’Brien, 1981).

In other words, military necessity is a principle of national security stewardship that demands that actions be directed at genuine military aims. Military necessity is concerned with the practical aspects of battlefield scenarios that must be considered in light of the imperatives of troop protection, the preservation of national interests, and victory (Patterson, 2007).  

Military necessity is not raw consequentialism. Military necessity should be particularly important to democracies because it protects the lives of citizens in uniform and is responsible with the use of that nation’s resources, both of lives and treasure. While it is true that the lives of warfighters might be spent by a military commander—including or especially a just military commander—those lives must never be wasted. 

Jus Ad Bellum

“For a war to be just,” writes Thomas Aquinas, “three things are necessary”: sovereign authority, just cause, and right intention (Aquanis). As James Turner Johnson observed, these correspond directly to what Augustine identified as the three goods of the political community: order, justice, and peace. The just war tradition is set within a larger moral framework of good politics oriented to a just and peaceful order in which “the use of armed force is a necessary tool to be used by responsible political authority to protect that just and peaceful order in a world in which serious threats are not only possible but actual” (Johnson, 2005a).

Right authority

Rightly understood, therefore, the sovereign is the one over whom there is no one greater charged with the preservation of the order, justice, and peace of the political community. Because of this, “the natural order,” Augustine writes, “which seeks the peace of mankind, ordains that the monarch should have the power of undertaking war if he thinks it advisable” (Johnson, 2005b). Johnson elaborates:

Within this conception of politics, the ruler’s right to rule is defined by his responsibility to secure and protect the order and justice, and thus the peace, of his own political community and also to contribute to orderly, just, and peaceful interactions with other such communities…The use of armed force in this conception was thus both strictly justified and strictly limited: it might be undertaken only on public authority and for the public good (Johnson, 2005b).

This conception of sovereign rule as defined by sovereign responsibility takes its bearings from Romans 13:4: “For the one in authority is God’s servant for your good. But if you do wrong, be afraid, for rulers do not bear the sword for no reason. They are God’s servants, agents of wrath to bring punishment on the wrongdoer” (NIV).

Only a person, or persons, in a position of responsibility for the upkeep of the political community may authorize the use of the sword. Except in rare exceptions of extreme emergency, anyone else who deploys the sword—usurping the proper function of an existing sovereign—is guilty of disturbing the peace and order of the political community, no matter what the cause. While it is self-evident that a wise ruler will consider the counsel of well-informed advisors, it remains that the ultimate responsibility for the decision to use force rests with the sovereign. 

Grounding sovereignty in moral responsibility contrasts significantly with the concept of sovereignty stemming from the 1648 Peace of Westphalia. Too often, the latter, morally sterile conception, has proved that “the principles of national sovereignty, territorial integrity, and noninterference in domestic affairs can, if interpreted in strictly procedural terms, conduce to protect tyrants while they oppress, rob, torture, and kill the citizens of their nations” (Johnson, 2005b).

Just Cause

The fundamental question is when ought just societies employ force against evil? In response, the just war framework envisages three causes: protection of the innocent, recovery of what has been wrongly taken, and the punishment of evil.

The qualifier in each of these causes – ‘innocent’, ‘wrongly’, ‘evil’ – is crucial. The reason for each is most easily seen by examining the first cause. It would be insufficient to name—as positive international law names—self-defense against attack as a just cause. Indeed, when commenting on just cause Aquinas lists only recovery of what has been wrongly taken and punishment of evil. Why the absence of defense of the self or others? It is not that Aquinas does not believe that a sovereign has the right to defend his realm against attack. On the contrary, he makes a greater allowance than Augustine for even private self-defense when he insists” a man is under a greater obligation to care for his own life than for another’s” (Aquanis). Pope John Paul II later channeled this Thomistic assertion when he connected self-love with a “culture of life”: 

The intrinsic value of life and the duty to love oneself no less than others are the basis of a true right to self-defense…The demanding commitment to love your neighbor presupposes love of oneself as the basis of comparison. Legitimate defense can be not only a right but a grave duty for someone responsible for another’s life, the common good of the family or of the State (John Paul II, 2001)

In the classical just war view, the defense of the common good is the central rationale for just war as a whole. Insofar as the need for defense provides a just cause, it does so on the basis of the sovereign’s responsibility to protect order and justice (Johnson, 2005b) The reason that the qualifier in “protect the innocent” is so important is now clear: only the innocent have a right to be defended. To insist otherwise, to propose national sovereignty without qualification as a human good, and thereby to make national self-defense simply the model of justified war, is amoral. It ignores questions of motive, intention, cause, and the moral quality of the regime and issues in some counter-intuitive judgements. It implies, for example, that as soon as the Allies invaded the borders of Germany in 1945, Hitler’s belligerency became self-defensive and so justified, and the Allies’ war-making became aggressive and so unjustified (Biggar, 2016). 

It is in avoiding such absurdities that the Christian just war tradition’s refusal to take national self-defense as its paradigm marks its difference from—and superiority to—those recent ways of thinking about war rooted in certain branches of moral philosophy, such as Michael Walzer’s (Walzer, 1977) – at least, as represented by David Rodin (Rodin, 2005). 

The Christian view is that, since justified war is always a response to a grave injustice, it must always aim to rectify that injustice. This response may take defensive or aggressive forms. It may move seamlessly from defense to aggression, or it may begin with aggression. Justified aggression is what so-called “humanitarian intervention” is all about. The doctrine of the Responsibility to Protect (R2P) is, in effect, a reassertion of the Christian paradigm of justified war (Biggar, 2016).  Importantly, the Episcopal Church urges all its members to understand and reflect upon the R2P principle, and to advocate for it adherence (General Convention resolution 2012-A016).

This responsive, reactive posture is essential. The just war view can never countenance the initiation of violence. It may be, perhaps, that the sixteenth century Caribbean would have been better off with the Christian religion, or that nineteenth-century China would have benefitted from the free trade of opium. The conferring of such benefits, however, could never amount to a just cause for waging war on them (Biggar, 2013a). When given a simple choice between violence or non-violence, the just war view will always choose non-violence. The point is that just war analysis kicks in only when violence—or the clear and credible threat of it—is already unjustly perpetrated, and the only thing now in question is the manner of response. 

Put another way, the Christian view of just cause allows that a war is justified only when it intends to stop and correct a grave injustice that threatens genuine and important human goods or those social and political matrices upon which the flourishing of individual persons depends (Biggar, 2013b) As it is reactive against injustice and defensive of justice, the just war use of force is also, in essence, punitive. This renders war a necessarily moral enterprise. It is not about defending, without evaluation, “whatever borders history or positive law happens to have posited, nor about maintaining a stable regional status quo, regardless of the evils behind those borders or the justice that could be done in transgressing them” (Biggar, 2013b) 

Some argue that such a view of war risks fostering moral self-righteousness and loosening the reins of war. It is true that the Christian just war tradition encourages intervention, but it is untrue that it—therefore—encourages conflict. The fact that there is cause to intervene in the first place means that the opportunity to avoid conflict is already past. 

While it is also true that this will require some to make moral judgments over others, this ought not to deter us. Justice may be blind, but she holds scales—the pursuit of justice turns on the ability to weigh basic distinctions and assign moral value. Ethical clarity in a time of war is largely about distinguishing critical dissimilarities between acts that might look remarkably similar: between assault and self-defense; terrorism and revolution; justice and revenge; killing and murder, and so on.

The making of judgements need not be judgmentalism or arrogance. Knowing something about the poor condition of their own souls, Christians, above all others, should be theo-anthropologically allergic to thinking that the just warrior stands against the unjust perpetrator as simply righteous against unrighteous, clean against unclean (Biggar, 2013a). In fact, the punitive nature of just war is grounded in the recognition of the dignity of those we punish. To respond appropriately to the moral choices of others is to take their status as moral beings seriously. It is to acknowledge that what they will and decide to do actually matters. It says they are significant.

Right intention

What is the goal of a just war? This can be treated in two ways. Negatively, the intention must be to avoid evils. As Augustine puts it: “The real evils in war are love of violence, revengeful cruelty, fierce and implacable enmity, wild resistance, and the lust of power, and the like” (Augustine) As noted, the ius in bello framework helps prevent these by mandating proportionate force and due care in targeting. On the positive side, as we have already seen, war is waged with the intention of punishing these ’real evils’. But there is more.

For Augustine, the purpose of war was always, and primarily, to restore a disordered peace. In his letter to Boniface, the Roman military tribune in north Africa, Augustine insisted: “Peace should be the object of your desire; war should be waged only as a necessity…in order that peace may be obtained” (Augustine, 1887).

Better still is what Augustine calls tranquilitas ordinis—”the tranquility [or peace] of order.” Such peace is not externally compelled but rather internally prompted by love of God and neighbor. This peace, Augustine writes in The City of God, is born of a commitment that “one will be at peace, as far as lies in him, with all men.” The basis of this commitment is “the observance of two rules: first, do no harm to anyone, and, secondly, to help everyone whenever possible.” This will not result, Elshtain cautioned, in “the perfect peace promised to believers in the Kingdom of God, the one in which the lion lies down with the lamb.” Against this vain hope, political ethicist Jean Bethke Elshtain wryly observed: “On this earth, if the lion lies down with the lamb, the lamb must be replaced frequently” (Elshtain, 2003).

Nevertheless, Elshtain saw this pursuit of a tranquilitas ordinis as central to what good politics is all about. Peace is to be the product of order and justice, without which no other political goods can long perdure. What political goods did she have in mind? Quotidian ones:

“Mothers and fathers raising their children; men and women going to work; citizens of a great city making their way on streets and subways; ordinary people flying to California to visit their grandchildren or to transact business with colleagues—all of these actions are simple but profound goods made possible by civic peace. They include the faithful attending their churches, synagogues, and mosques without fear, and citizens—men and women, young and old, black, brown, and white—lining up to vote on Election Day.” (Elshtain, 1998).

Here we come to a humility of purpose: there is only so much we can do. But “in this world of discontinuities and profound yearnings, of sometimes terrible necessities,” Elshtain mused, “a human being can yet strive to maintain or to create an order that approximates justice, to prevent the worst from happening, and to resist the seductive lure of grandiosity” (Elshtain, 1998). 

Taken together, right authority, just cause, and right intent are the primary criteria regarding when it is justified to use force. Deontological in nature, they impose the burden of duty on those bearing ultimate responsibility for the good of the political community and for good relations among political communities. Otherwise put, the jus ad bellum requirements, if satisfied, do not point to when it is merely permissible to consider force but rather when it is obligatory. Secondary, prudential considerations regarding last resort, proportionality, probability of success, and the like serve as cautionary filters. 

It may be that simply because something is right to do, it might not be wise to actually do it. In such cases, when proper prudence dictates that we stand down despite the just cause arrayed before us, the decision not to fight should register as a tragedy. It can only mean that, for now, some innocents will not be protected, some injustice will remain unrequited, some great evil will go unpunished.

For Augustine, the impossibility of peace was a tragedy. He lamented: “A just war is justified only by the injustice of an aggressor, and that injustice ought to be a source of grief to any good man, because it is a human injustice”(Augustine, 2003). Given the heavy nature of this task, the demeanor of the Christian soldier is paramount. Augustine insisted that “no one is fit for inflicting this punishment except the man who, by the greatness of his love, has overcome that hatred wherewith those are wont to be inflamed who wish only to avenge themselves.” 

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Works Cited

Aquinas, Thomas. Summa Theologiæ, n.d., II-II.40 

Augustine, The City of God, trans. Henry Bettenson (London; New York: Penguin Books, 2003), cf. BK XIX, esp. p.chs. 13-p.17.

Augustine. “Contra Faustum,” in Nicene and Post-Nicene Fathers, ed. Philip Schaff, trans. Richard Stothert, vol. 4 (Buffalo, NY: Christian Literature Publishing Co, 1887), XXII.75.

Augustine (2001). “Letter 138 (to Marcellinus),” in Political Writings, ed. E. Margaret Atkins and Robert Dodaro (Cambridge: Cambridge University Press, 2001).

Augustine (1887). “Letter 189, To Boniface,” in Nicene and Post-Nicene Fathers, ed. Philip Schaff, trans. J.G. Cunningham, vol. 1 (Buffalo, NY: Christian Literature Publishing Co, 1887).

Biggar, Nigel (2013b). In Defence of War (Oxford: Oxford University Press, 2013).

Biggar, Nigel (2016). “In Defence of Just War: Christian Tradition, Controversies, & Cases,” Providence: A Journal of Christianity & American Foreign Policy, no. 4 (Summer 2016): 14.

Biggar, Nigel. (2013a) Natural Flourishing as the Normative Ground of Just War: A Christian View,” in Just War: Authority, Tradition, and Practice, ed. Anthony F. Lang Jr, Cian O’Driscoll, and John Williams (Washington, DC: Georgetown University Press, 2013), 51.

Calvin, John. Institutes of the Christian Religion, trans. Ford Lewis Battles (Westminster John Knox Press, 1960), 4.20.11.

Calvin, John (1973). Letter to the duchess of Ferrara, January 24, 1564, trans. M.R. Gilchrist, in The Letters of John Calvin, ed. Jules Bonnet (New York: B. Franklin, 1973), vol. 4, 356-57.

Coates, A.J. The Ethics of War (Manchester, Manchester University Press, 1997), 235-7.

Corey, David D. and J. Daryl Charles. The Just War Tradition: An Introduction (Intercollegiate Studies Institute, 2014), 100–101.

Elshtain, Jean Bethke (2003). Just War against Terror: The Burden of American Power in a Violent World (New York: Basic Books, 2003), 46.

Elshtain, Jean Bethke (1998). Augustine and the Limits of Politics, 1st edition (Notre Dame, Ind.: University of Notre Dame Press, 1998), 111.

Hartigan, Richard Shelby. Lieber’s Code and the Law of War (Precedent Press, 1983).

John Paul II, Evangelium Vitae, in J. Michael Miller, ed., The Encyclicals of John Paul II, 2nd edition (Huntington, Ind: Our Sunday Visitor, 2001), 772–894, sections 55.1 and 55.2.

Johnson, James Turner (2005a). The War to Oust Saddam Hussein: Just War and the New Face of Conflict, first edition (Lanham, Md: Rowman & Littlefield Publishers, 2005), 16.

Johnson, James Turner (2005b).  “Just War, As It Was and Is,” 14. https://www.firstthings.com/article/2005/01/just-war-as-it-was-and-is

LiVecche, Marc. The Good Kill: Just War & Moral Injury (Oxford University Press, 2021).

O’Brien, William V.  The Conduct of Just and Limited War (Praeger, 1981), 9.

O’Donovan, Oliver (1989).  Peace and Certainty: A Theological Essay on Deterrence (Oxford: Clarendon, 1989).

O’Donovan, Oliver (2003). The Just War Revisited (Cambridge: Cambridge University Press, 2003)

Patterson, Eric. Just War Thinking (Lexington Books, 2007).

Ramsey, Paul. War and the Christian Conscience (Durham, NC: Duke University Press, 1961).

Ramsey, Paul. The Just War: Force and Political Responsibility (Savage, MD: Rowman & Littlefield, 1968)

Rodin, David. War and Self-Defense (Oxford: Clarendon Press, 2005), 108.

Solis, Gary.  The Law of Armed Conflict: International Humanitarian Law in War (Cambridge University Press, 2010).

U.S. Department of Defense Law of War Manual, 2016, 52.  Available at: https://dod.defense.gov/Portals/1/Documents/pubs/DoD%20Law%20of%20War%20Manual%20-%20June%202015%20Updated%20Dec%202016.pdf?ver=2016-12-13-172036-190.

Vattel, Emer de. The Law of Nations (Indianapolis: Liberty Fund, 2008), 571-72.

Walzer, Michael. Just and Unjust Wars: A Moral Argument with Historical Illustrations (New York: Basic Books, 1977).

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