Limited Force and the Fight for the Just War Tradition

Limited Force and the Fight for the Just War Tradition, by Christian Nikolaus Braun, (Washington, D.C.: Georgetown University Press, 2023), 288 pp., cloth $134.95, paperback $44.95.

In some ways, Christian Braun’s new book Limited Force and the Fight for the Just War Tradition can be understood as a work of scholarly diplomacy. For more than two decades, there has been something of a rupture within the ever-burgeoning field of just war studies, between scholars who adopt a more historical and legalistic approach (referred to broadly as the “traditionalist” or “classical” camp) and those who prefer a strictly moral, analytical approach, applying the same ethical reasoning and expectations to war as they do to everyday life (known as “revisionist” just war theory).

While the two camps have indeed responded to one another over the years, Braun correctly points out that much of the debate has been characterized by scholars on each side talking at each other rather than with each other. The result is that valid contributions and criticisms offered by both sides have rarely been successfully synthesized. Braun endeavors in this new book to show where synthesis may be possible. The area he chooses to focus on is that of vis (force) and the debate around what has come to be referred to as jus ad vim: the just use of force short of war. The types of force on which Braun concentrates are targeted killings and limited strikes (typically remote missile strikes).

In his analysis of jus ad vim, Braun develops a novel methodology, combining just war, casuistry, and virtue ethics. In doing so, Braun’s approach is markedly historical, deeply influenced by the thought of Thomas Aquinas and his modern interpreters, especially Gregory Reichberg. To an extent, one could describe Braun’s study as a Thomistic account of jus ad vim; however, this would fail to properly recognize the various other influences underlying Braun’s argument, which hail from both the traditionalist and revisionist just war camps.

The book is organized into three parts. In part 1, Braun outlines the main points of contention within contemporary just war literature between traditionalists and revisionists, and provides an overview of how the two camps have approached the doctrine of jus ad vim. In doing so, he offers a lesson in concise, lucid, and balanced analysis, and readers who are unfamiliar with the historiography of the field will find this an extremely useful resource. In part 2, Braun turns to the just war thought of Thomas Aquinas and its modern interpreters, before explicating and justifying his own Thomistic-inspired methodology. Essentially, Braun utilizes a deontological approach (asserting the existence of certain moral norms) combined with casuistry: “testing” the normative standards by applying them to a series of historical cases. In part 3, Braun applies his casuistic methodology over the course of four chapters, offering a series of cases, analysis, and conclusions. The cases are almost exclusively drawn from twenty-first-century conflicts involving the United States.

The dual influence from the traditionalist and revisionist just war camps is apparent throughout the book. This is most obvious in Braun’s sensitive handling of the debate between Daniel Brunstetter and Helen Frowe—broadly representing the traditionalist and the revisionist camps, respectively—on the relative merits of vis as a distinct category of military force independent of war (bellum). Brunstetter has been at the forefront of carving out a moral and legal space for the legitimate use of vis, with the intention of avoiding escalation to full war. Yet Brunstetter’s defense of vis as a separate moral category from bellum has been vigorously challenged by Frowe, who argues that, as a moral category, vis is redundant, because it adds nothing to the process of reasoning that is not already contained within the just war framework. Finding merit in the arguments of both scholars, Braun offers his book as a “third way,” producing a nuanced and sophisticated argument in favor of deploying limited force in the international arena (pp. 26–27).

In defending his casuistic methodology, Braun turns to Aristotelian/Thomistic virtue ethics as a means to curtail the abuses that such an approach can encourage (such as probabilism, in which prudential reasoning can justify immoral actions). He also insists that historical cases—rather than imagined ones—should be the bread and butter of just war theorists.

By stressing Aquinas’s just war condition of “right intention,” Braun seeks to limit the extent to which the use of casuistical analysis might justify violence that is immoral, disproportionate, or escalatory (or all three). This reviewer is deeply skeptical about the effectiveness of virtue ethics as a means to encourage military restraint, but Braun’s proposal of applying virtue ethics as a secondary assessment of moral cases (rather than as a primary assessment of the moral permissiveness of a direct action) represents a deft turn. In Braun’s analytical process, the heavy lifting is performed by his deontological claims, which are tested using historical cases to determine their validity and effectiveness. Only then does he turn to virtue ethics as a “backstop” to further encourage policymakers and combatants to abide by their moral standards.

Above all, Braun seeks to promote just war reasoning as an applied resource, utilized to inform policy decisions on whether or not to use force, where to use it, and how to use it. With this practical end in mind, Braunmaintains that it is essential that such reasoning stays grounded in the real experiences of conflict, rather than retreating to the hypotheticals of the ivory tower. Braun insists that his casuistic approach does not associate with any particular ethical theory, though he adopts broadly Thomistic Catholic moral principles as “the baseline of analysis” (pp. 56–58).

By far the most controversial element of Limited Force and the Fight for the Just War Tradition, developed during parts 2 and 3, is Braun’s defense of retributive violence. Arguing that Aquinas saw punishment and retribution as essential components of just war, Braun posits that the retributive targeted killing of culpable individuals is morally defensible (p. 155). However, it remains a little unclear whether culpability should be determined solely on the basis of international law judgements or on the basis of Braun’s moral framework, or a combination of the two. He limits his defense of retributive killing somewhat by arguing that assassinating non-state actors is less risky (in terms of escalation) than assassinating representatives of a sovereign state, and is therefore more justifiable on prudential grounds. He also argues that such killings should not disproportionately endanger innocent bystanders (p. 158). Given these limitations, he expects the number of such targeted killings to be minimal.

Going further, Braun argues that preemptive targeted killings can be justified. He observes that a “calculus” should exist to determine the acceptable amount of time separating a threatened enemy action from the launch of a pre-emptive strike, as well as determining the level of acceptable collateral damage (p. 164). However, he does not provide such a calculus, leaving it instead to policymakers. This seems rather wooly, and provides no clear sense of when a licit preemptive action becomes an illicit preventative action.

It is this element of Braun’s account where there is a level of faith in the prudence and morality of political and military leaders that, given what we know about the conduct of modern conflicts and the horrendous levels of non-combatant casualties, will strike many readers as overly optimistic. Braun seems content to appeal to the guiding hand of virtue ethics but, again, not everyone will find this reassuring. Similarly, when Braun justifies attacking the palaces of dictators as an act of retribution, his suggestion that civilian casualties could be reduced by issuing a prewarning seems to ignore reality (pp. 212–13). A dictator might consider it to his or her advantage if as many civilians as possible were harmed in such an attack, as this would constitute a propaganda coup.

Braun’s willingness to justify retributive force is also brought to bear in permitting the use of air strikes against states that have violated international norms. Braun urges that norm violation would need to be of “significant importance” and of sufficient “magnitude” to justify retributive strikes. For example, he writes, “The hosting and supporting of terrorist groups that lead to actual attacks, plotting illicit acts of vis, and using weapons of mass destruction against one’s own population seem to cross this threshold” (p. 206). This strikes me as far too permissive. For example, it would permit almost constant punitive attacks against a state like Lebanon (which hosts Hezbollah) and would have justified British strikes on the Republic of Ireland during the period of the Troubles (which hosted the IRA). The potentially broad utilization of such retributive violence is curtailed, however, by Braun’s appeal to prudential reasoning, insisting that retributive uses of vis should not catastrophically escalate a conflict. He thus draws a distinction between striking weak states and striking “great power” states, advising against the latter due to prudential fears concerning an escalation into nuclear war (for example, NATO’s reluctance to intervene directly in Ukraine against Russia). To Braun, striking weak states or non-state actors is legitimate because their retaliatory capacity is limited. Can such reasoning truly chime with a moral approach to vis? If anything, this seems more like Thucydidean realism, where the strong do as they wish and the weak suffer what they must.

Regardless of whether one agrees with Braun’s claims for the application of jus ad vim in practice, there is no doubt regarding the value of his successful attempt to bring the two camps of just war studies into meaningful dialogue. Throughout this thoughtful study, Braun highlights that there are as many—if not more—similarities and agreements between the two camps of just war studies as there are differences. In using historical cases to evaluate his normative claims, Braun has mimicked the analytical approach of the revisionist camp. Where he differs is in his insistence that such cases should not be fictitious thought experiments but real actions drawn from history, which are hopefully of greater relevance when determining justified military action in the present. Drawing on Aquinas and a host of other historical just war commentators, his moral framework remains committed to the traditionalist assertion that the moral force of contemporary just war doctrine is partly rooted in its historical heritage and longevity. And yet he is also more than willing to embrace and adapt revisionist critiques of that same historical tradition. Limited Force and the Fight for the Just War Tradition is not only an insightful contribution to the literature but an encouraging one.

—Rory Cox

Rory Cox is a senior lecturer in medieval history at the University of St Andrews, an associate fellow of the Handa Centre for the Study of Terrorism and Political Violence, and chair of International Studies Association’s International Ethics Section.