The Russia-Ukraine war demonstrates the crucial role of technology in modern warfare. The use of digital networks, information infrastructure, space technology, and artificial intelligence has distinct military advantages, but raises challenges as well. This essay focuses on the way it exacerbates a rather familiar challenge: the “civilianization of warfare.” Today's high-technology warfare lowers the threshold for civilian participation in the war effort. A notable example is the widespread use of smartphone apps by Ukrainian civilians, who thereby help the armed forces defend against Russian aggression. Through the lenses of international humanitarian law, conventional just war theory, and revisionist just war theory, this essay evaluates the normative dimensions of such civilian participation. The analysis shows that civilians can lose their legal protections when they use these apps to directly participate in hostilities, and this loss of immunity can be justified by Michael Walzer's conventional just war theory. Revisionism, however, puts the justness of the war at the forefront, and so sheds doubt on the moral liability of Ukrainian civilians. Considering the broader implications, including the blurring combatant-civilian distinction, indicates that such civilianization of warfare should not be welcomed; the risks will often outweigh the benefits. At a minimum, states ought to exercise restraint in mobilizing civilians and inform them of the implications of their actions.

One of the most pronounced features of the war in Ukraine has been the heavy reliance of the Russian forces on convict-soldiers, most notably by the private military and security company (PMSC) the Wagner Group. In this essay, I explore the ethical problems with using convict-soldiers and assess how using them compares to other military arrangements, such as conscription or an all-volunteer force. Overall, I argue that the central issue with using prisoners to fight wars is their perceived expendability. To do this, I present three arguments. First, although many prisoners have been under major duress, using convict-soldiers may be somewhat preferable to using conscripts in this regard. Second, convict-soldiers are more likely to be subject to human rights abuses than other types of soldiers and this should be seen as the main problem with their use. Third, convict-soldiers’ liability to lethal force for fighting in an unjust war does not render it permissible to treat them as expendable.

Michael Walzer's use of John Stuart Mill's A Few Words on Non-Intervention (1859) helped to inaugurate it as a canonical text of international theory. However, Walzer's use of the text was highly selective because he viewed the first half as a historically parochial discussion of British foreign policy, and his interest in the second was restricted to the passages in which Mill proposes principles of international morality to govern foreign military interventions to protect third parties. As a result, theorists tend to see those canonized passages as if through a glass darkly. Attention to the detail and context of Mill's first-half critique of Lord Palmerston's opposition to the Suez Canal project reveals that his discussion of purely protective intervention is embedded in a broader exploration of the limits of self-defence, including the moral permissibility of preventive military force and the use of protective interventions for defensive purposes. Moreover, reading the text holistically facilitates a refutation of some objections directed at it by Michael Doyle to the effect that Mill's conception of self-defence incorporates elements of aggression which makes it extremely dangerous when adapted for application to the contemporary world.

Suppose that state A attacks state D without warrant. The ensuing military conflict threatens international peace and security. State D (I assume) has a justification for defending itself by means of military force. Do third parties have a justification for intervening in that conflict by such means? To international public lawyers, the well-rehearsed and obvious answer is “yes.” Threats to international peace and security provide one of two exceptions to the legal and moral prohibition (as set out in Article 2[4] of the UN Charter) on using force as a means for resolving interstate disputes. Just war theorists are not as verdictive. Compared to the ethics of humanitarian intervention and the ethics of national self-defense, the ethics of third-party military involvement in interstate conflicts remains underdeveloped in contemporary just war theory. This essay begins to fill that gap. I argue that to defend such interventions is tantamount to defending preventive military force, deterrent military force, and the resort to force in more cases than standardly thought. I then provide an account and limited defense of the deterrence argument. I show that deterrence is morally justified in relatively few cases and examine two problems with the argument: deterrence failures and the level of uncertainty under which leaders who use deterrent force operate. I conclude that we should take seriously the possibility that nonintervention, construed as the rejection of the direct use of military force, is the morally correct response to the most serious threats to international peace and security.

This essay contends that the ethics around the use of spy technology to gather intelligence (TECHINT) during espionage and counterintelligence operations is ambiguous. To build this argument, the essay critically scrutinizes Cécile Fabre's recent and excellent book Spying through a Glass Darkly, which argues that there are no ethical differences between the use of human intelligence (HUMINT) obtained from or by human assets and TECHINT in these operations. As the essay explains, Fabre arrives at this position by treating TECHINT as a like-for-like replacement for HUMINT. The essay argues instead that TECHINT is unlikely to act as a like-for-like replacement for HUMINT. As such, TECHINT might transform existing practices of espionage and counterintelligence, giving rise to new ethical challenges not captured in Fabre's analysis. To illustrate the point, the essay builds an analogy between TECHINT and recent armed conflicts in which precision weapons have been deployed. Although precision weapons seem ethically desirable, their availability has created new practices of waging war that are ethically problematic. By analogy, TECHINT, though not intrinsically undesirable, has the capacity to generate new practices of intelligence gathering that are ethically problematic—potentially more than HUMINT. Ultimately, recent negative experiences with the use of precision weaponry should caution against an overly positive assessment of TECHINT's ethical desirability.

In this essay, I reflect on the divergent arguments about limited force made by Daniel R. Brunstetter and Samuel Moyn in their respective monographs. Arguing that their positions can be reconciled, I agree with Brunstetter that limited force has a role to play in establishing and maintaining a just world order. At the same time, however, I am mindful of Moyn's warning that limited force may lead to perpetual war. The way to ensure that limited force both works toward justice and does not result in perpetual war, I argue, is to focus more on considerations of jus ante bellum (right before war) and jus post bellum (right after war), the so-called “growing edges of just war theory.” I hold that the responsible use of statecraft, which just war thinking seeks to inform, accepts that limited force constitutes a legitimate tool to facilitate order, justice, and peace. However, any justifiable use of force must be restrained and limited and aim for a just peace. The embrace of limited force should thus be complemented with an effort by state leaders to bolster the edges of just war in order to facilitate a security environment that requires the use of limited force less frequently.

When should peacekeepers partially or fully withdraw from a country or region in which they are operating? This important question has received little scholarly attention. However, it has profound implications. If peacekeepers depart prematurely, as happened in Rwanda in 1994, the consequences can be disastrous with the potential to lead to widespread preventable deaths and human suffering. If they overstay, peacekeepers risk alienating the population they are seeking to protect and undercutting popular sovereignty at significant economic costs. Striking a balance, we propose a framework for just withdrawal that is both normatively compelling and empirically sound. It focuses on three aspects that are vital for understanding when peacekeepers can depart in an ethically justified manner: just cause, effectiveness, and legitimacy. By considering a number of objections, we also address critics who challenge the overarching premise of peacekeeping or might prefer different standards by which to suggest peacekeepers should stay or depart. Finally, we illustrate our argument with theoretical and empirical examples and a discussion of UN peacekeeping in East Timor.

Just war theory appears ever more alienated from the practice it ostensibly regulates, warfare. An increasingly abstract and esoteric discourse, it can seem very remote from the mud-and-blood actualities of warfare. This is reflective of a broader disconnect between the study of, on the one hand, the ethics of war, and, on the other, the lived experience of war. Seeking to address this problem, this article asks: How can we recentre just war thinking as a ‘lived’ theory? It proposes that we can reconnect just war theory to the lived experience of warfare by restoring its historical dialogue with existentialism. It develops this position by reading just war theory through the prism of Albert Camus's writings on political violence. It concludes that Camus's political thoughts provides a set of signposts for the development of a mode of just war theorising that places that the lived experience of warfare at the heart of our ethical thinking about war.

As part of the roundtable, “Moral Injury, Trauma, and War,” this essay explores the relationship between revisionist just war theory and moral injury. It proceeds in four sections. First, it offers a brief overview of the just war tradition, focusing on traditionalist and revisionist accounts, respectively. Next, it explores the relationship between moral injury and armed conflict. Then, it explores the links between moral injury and revisionist accounts of just war theory. Finally, by way of conclusion, the essay signals two potential complementary paths forward that future research could use to clarify the revisionist position and its link with moral injury.