Writing during the Bosnian War in October 1992, John F. Burns reports that only a single animal remained alive in Sarajevo’s zoo after the city had been under siege for four months:

The scene in the animal house is wrenching. A putrid odor pervades the concrete building, and cage after cage is littered with the carcasses of lions, tigers, leopards and pumas. From the skeletal remains of some and the whole carcasses of others, it is clear that some died sooner than others, and that their surviving mates fed on the bodies before they, too, succumbed to hunger. … In the cage where there were once four bears, the sole survivor prowls amid the jawbones and rib cages and tufted skins of the others. The big cats and bears and wolves lasted longer than the giraffe, the ponies and the buffaloes, which were in paddocks exposed to Serbian positions when the siege set in. By midsummer, they were dead, shot out of pity, perhaps, or maybe for target practice.

Scholars and activists are increasingly concerned about the impact that warfare has on animals. Two separate books called Animals and War have been published by scholars in (critical) animal studies in the last decade, while there has been an ongoing campaign by animal protectionists in the UK aiming to ban warfare-related experiments on animals, leading to a well-signed Early Day Motion in the House of Commons. But one thing that has seen very little attention is the place of animals in just-war theory.

Just-war theory is a tradition of Western thought concerned with the ethics of war, with roots in early Christian and Roman thought. It has had significant influence on the creation of international law regarding war, in, for instance, the Geneva Conventions. Its key idea is that, though regrettable, war is sometimes morally justifiable.

In – very – brief, just-war theory posits two categories of requirements that a war needs to satisfy in order to count as ‘just’. On the one hand, there are requirements concerning when groups may resort to war (jus ad bellum, or ‘right to war’). On the other, there are requirements about the right conduct during war (jus in bello or ‘right/justice in war’). Both jus ad bellum and jus in bello have a range of criteria that must be met for a war (or action within a war) to be just. While we will introduce some of these criteria shortly, we won’t try to summarise them all. If you are interested, you can read more about just-war theory here.

In a forthcoming paper in the journal Social Theory and Practice, we make the case for counting animals in just-war theory. While we think that all of the criteria of just-war theory raise important questions about animals, we think that the criteria that should be addressed first are necessity (including last resort, which is closely related) and proportionality. Necessity is a requirement of jus in bello. It requires that any harm caused by an action must be necessary to achieve the intended war aim – that the war aim could not be achieved without that harm (or greater harm). Last resort is a bit like the jus ad bellum version of necessity: it requires that less harmful feasible alternatives to war must be tried before war is declared. Proportionality, meanwhile, appears in both jus in bello and jus ad bellum. It requires that the good achieved by the war (or action within war) must not be outweighed by the harm caused by the war (or action). We address these criteria in particular because most of the animals impacted by war are not deliberately targeted – they are, to use an unpleasant euphemism, collateral damage. The requirements of last resort/necessity and proportionality (both ad bellum and in bello – that is, both when making decisions about whether to wage war and how to wage war) are the requirements that most directly concern such non-deliberate harm. Including animals in our assessments of proportionality and necessity thus, we argue, enables us to make a meaningful difference in terms of how animals are affected by war.

What does it mean to consider animals when it comes to calculating proportionality and necessity? Well, it means that when we’re deciding whether a war or an action in war is necessary or proportionate, we include animals’ interests in the mix. At the moment, only the harm to humans is counted when it is asked whether a war (or action in war) is necessary or proportional. We think that harm to humans and animals should be counted. In war, animals are made to suffer, and they are killed. Wild animals lose their habitats. Domesticated animals lose their caregivers. All of these things are contrary to animals’ interests, and need, we think, to be taken into account. If lots of bad things are happening to animals, that means that it’s going to be harder to justify waging war.

Let us illustrate this with an example. Imagine a rogue state is posturing against a neighbour, and, if allowed to continue, will likely launch increasingly significant attacks, leading to escalating clashes. Imagine that this neighbour’s powerful allies are trying to determine whether to launch a war against the rogue state. These allies determine that a war would threaten the lives of a number of soldiers on both sides, but that it would be a proportional response to the threat of clashes.

At least, it would be if only human interests are taken into account. Perhaps, however, the conflict would take place in an area populated by many animals, and so predictably lead to a great deal of animal suffering. We think that this suffering should be included in the calculation of whether this war is proportional. While before we might have thought the war proportional, it could be the case that a war envisaged to threaten a number of soldiers’ lives and lead to a great amount of animal suffering is not proportional. Counting animals in war – in this case, at least – leads us to avoid wars that we would otherwise be fighting.

In other cases, it might encourage us to utilise different, more animal-friendly, modes of fighting – the less animal-friendly methods might be deemed unnecessary, even while they would be ‘necessary’ if only human interests were taken into account. For example, in our paper, we imagine a case inspired by real-world stories of penguins thriving in minefields. Penguins are too light to trigger mines. Landmines, though, are not a human-friendly way to deter invasion. Clearly marked minefields do not pose that much of a threat to humans, but they do pose some threat. On the other hand, fortification of coastlines might pose no threat to humans, but a very great threat to penguins, who will be blocked from accessing the sea, and have their lives disrupted in the most profound ways. In this case, then, the ‘animal-friendly’ means of deterring attack would be the use of mines, not the use fortifications. Other cases might have different results entirely – in other contexts, mines pose a serious threat to both humans and animals. Naturally, it’s going to depend on the details of the particular conflict or action. In writing this paper, we are not saying that wars should always not be waged, or always be waged, or that particular methods of fighting should always be favoured over others. We’re just saying that animals’ interests should be taken into account when these decisions are made, and that this might change the result of the decision-making process.

But is any of this realistic? We might think that there is so much harm to animals in war that our proposal would leave war almost invariably unnecessary or disproportionate. Some people might think that this is a good thing – lots of animal advocates and vegans are antiwar advocates and pacifists. And, to be completely clear, we think that there would be no war in an ideal world, and we think that (at least!) many real-world wars are waged unnecessarily and disproportionately. But our proposal is hardly likely to be adopted by militaries if it simply amounts to a declaration of pacifism – and we believe that, under the non-ideal conditions in which we find ourselves, including animals in just-war theory could be a way to help actually existing animals in the real world, by encouraging modes of fighting less destructive of animals and discouraging military actions that will have a large impact on animals. Luckily for our proposal, we think that there are a few reasons to think that counting animals in war is compatible with waging war justly – though it will encourage us to change how and when we wage war in some cases.

First, we suggest, the kind of information and expertise that militaries would need to count animals in their proportionality and necessity calculations – information from ethology, ecology, and human-animal studies, for example – is already out there, if you only know where to look. While militaries do not often consult experts in these areas, they could do, and while military personnel are not usually trained in these areas, they could be. So it isn’t too difficult for militaries to have access to the necessary information. Second, we note – borrowing from animal-rights theory – that many animals do not have as strong a continued interest in life as do most humans. This means that, for the purposes of calculating proportionality and necessity, the death of an animal is usually less bad than the death of a human. (Of course, this is still compatible with it being a very bad thing – and we think it is!) Third, many of the methods of war that will be most harmful to animals, such as indiscriminate bombing, biological warfare, or nuclear weapons, are already condemned by just-war theorists for other reasons. Combined, these things mean that, with a little effort, militaries can count animals without having to give up on the idea of war altogether.

We hope that our proposal prompts some frank discussions about the waging of war, and helps to expand concern about animals into a new area. We think that there is a great deal of work that remains to be done on animals and warfare, and have already started asking further questions. For example, we are very interested in stories about being vegan in the military, and about militaries taking steps towards vegetarianism. We’re now asking our own questions about this – what would just-war theory say about veganism and vegetarianism for soldiers? Might just-war theory say that soldiers should be vegans or vegetarians? Watch this space.

Josh Milburn is a British Academy Postdoctoral Fellow in the Department of Politics and International Relations at the University of Sheffield and a member of the Sheffield Animal Studies Research Centre. He is a philosopher who is interested in questions about animals and food. He is a member of the Vegan Society’s Research Advisory Committee and a section editor of the journal Politics & Animals. https://josh-milburn.com/

Sara Van Goozen is an Associate Lecture in Political Philosophy at the University of York. She is interested in just-war theory and global ethics. Her book Distributing the Harm of Just War is forthcoming with Routledge.