Now in its third year, the Russian war of aggression against Ukraine remains at the very top of the international security agenda. This conflict has largely refocused the West's attention away from the counterterrorism and counterinsurgency campaigns that followed the terrorist attacks of September 11, 2001. In February 2022, German chancellor Olaf Scholz went so far as to declare that the invasion signaled a zeitenwende, or “dawn of a new era.”Footnote ¹ Russia's aggression and the threat of having to fight a peer or near-peer competitor raises difficult questions, many of which are ethical in nature. The essays gathered in this roundtable seek to provide answers to some of those questions. They are the result of a workshop I organized for the King's College London Centre for Military Ethics in October 2023. One of my ambitions for this workshop was to put leading academics working on the ethics of war into discussion with military practitioners, making sure to include Ukrainian voices. I was very fortunate to succeed in these objectives, and I am convinced that the published essays have benefited enormously from our conversations.

While the war against Ukraine raises many ethical questions, several of which are relevant beyond this particular war, there can be no doubt about the overall judgment of just war thinking. Russia's invasion of Ukraine is widely viewed as rivaling the status of the Second World War as a prototypically unjust war. But it is important to recall that Michael Walzer has famously argued that “war is always judged twice.”Footnote ² In that sense, clearly, Russia has been committing a double crime. Its war of aggression has been unjust in terms of both jus ad bellum and, in many respects, jus in bello. Thus, while there is near unanimous consent on the jus ad bellum unjustness, most of this roundtable's essays grapple with what might be seen as the more nuanced jus in bello concerns.

Russia's war conduct highlights many ethical issues, some of them as old as warfare itself and some of them new in character. Neil Renic, for example, covers the age-old topic of war crimes in his contribution. Any student of history will be aware of the sorry fact that the rules of war have been violated time and again over the centuries. In that sense, the atrocious war crimes committed by Russian forces in places such as Bucha could be seen as just another example of the horrors of war. However, as Renic argues in his essay, Russia's systematic jus in bello violations and the moral outrage they have caused have exacted a strategic cost on Moscow by helping to consolidate Western support for Ukraine militarily, politically, diplomatically, and materially.

James Pattison tackles another long-established practice in the history of warfare: the use of mercenaries. Indeed, the mercenary is not referred to as the world's second-oldest profession without a reason. The role played by the private military and security company the Wagner Group in the Russian war effort has received much attention, but in his contribution, Pattison investigates an under-discussed aspect of the company's operations; that is, the ethical issues arising from the use of convict-soldiers by Wagner. In particular, he assesses how this compares to other military arrangements, such as conscription or an all-volunteer force.

In addition to ancient practices that continue to be a part of modern warfare, the roundtable also engages with existing and evolving military technologies. In her essay, Sophia Anastazievsky analyzes Russia's use of nuclear coercion and argues for a moral obligation of third-party states to intervene in support of Ukraine. In particular, she makes two main arguments. First, she identifies a pro tanto duty of states to intervene to stop Russian human rights abuses and ensure Ukraine's right to political independence and territorial integrity. Second, she holds that the most important moral consideration in determining whether there is an all-things-considered duty for the international community to intervene militarily in Ukraine is Russia's nuclear coercion.

Turning from the most indiscriminate type of weapon to a much less destructive but still enormously impactful weapon in the war against Ukraine, Christian Enemark considers the morality of armed drones. Specifically, he engages with ethical questions arising from the use of drones by Ukraine within Russian territory. Following Walzer's distinction cited above, Enemark argues that while Ukraine's war is just in the jus ad bellum sense, adhering to the jus in bello principles is a moral requirement that should determine how it uses drones. Therefore, Russian civilians are not liable to attack, and this nonliability is undiminished by the injustice of Russia's war. Moreover, Enemark warns of the potential negative consequences of using drones to attack Russian cities, which in his eyes would achieve little or no self-defensive benefit, and could even be counterproductive.

Finally, Lonneke Peperkamp grapples with the role of emerging technology and the status of civilians. She explores the ethical implications of the civilian world being drawn into war far more easily and profoundly than in earlier eras, particularly through the example of Ukrainian civilians using their smartphones to identify Russian targets. She considers how we should weigh the moral benefits and risks of a technology-enabled civilianization of warfare.

It goes without saying that this collection of essays is unable to engage with all of the ethical issues presented by the war against Ukraine. Nevertheless, I hope that this roundtable will serve as a catalyst for further discussion and research. Above all, my wish is that this war ends soon with the outcome the just war tradition calls for; namely, a just peace.