Introduction
While the destruction of buildings and the infliction of physical injuries form the visible imprint of armed conflict, the minds of affected populations are its hidden victims. Recent studies examining the relationship between armed conflict and mental health provide strong evidence of their correlation and causal links.Footnote 1 According to the World Health Organization (WHO), “[o]ne in five people (22%) who have experienced war or conflict in the previous 10 years has depression, anxiety, post-traumatic stress disorder, bipolar disorder or schizophrenia”.Footnote 2 Indeed, the devastating toll of armed conflict on the mental health of civilians has been documented, for example, in contexts ranging from the Democratic Republic of the CongoFootnote 3 and Bosnia,Footnote 4 through PalestineFootnote 5 and Sudan,Footnote 6 to MyanmarFootnote 7 and Ukraine.Footnote 8 Although the ways in which individuals and communities suffer is subjective, cultural, contextual and dependent on the presence of particular vulnerabilities,Footnote 9 what is invariable is that armed conflict inflicts deep, distressing and often debilitating scars on the human mind.
Existing documentation leaves little room for doubt that situations of armed conflict generate widespread harm to the mental health of affected populations; more difficult to establish, however, is what precisely causes a particular mental health impact. Such impacts are often not the result of a single, discrete event. In contemporary conflicts, civilians are typically subjected to a succession of traumatic experiences with cumulative effects, from bombings and deprivation of essential goods and services to displacement, discrimination and marginalization. In his 2024 report on the protection of civilians in armed conflict, the United Nations (UN) Secretary-General writes that
[c]ivilian harm in contemporary conflicts has multiple sources and is complex, overlapping, cumulative and long term. For example, it can be direct, in the form of death, injury and mental trauma. It can often be indirect, resulting from the destruction of critical infrastructure such as hospitals, water and power systems, as well as transport networks and agricultural and other means of production which impact the provision of essential services and health care and the availability of food and other essentials, leading to hunger, disease and further civilian deaths. Civilian harm is inherent in the displacement of civilians, who are at risk of further violence of different forms and have limited, if any, access to food, water, shelter and other assistance, causing yet further harm.Footnote 10
The fact that the causes for mental suffering in armed conflict are numerous and interlinked can create significant challenges for assessing responsibility for the wrongful infliction of mental harm under international humanitarian law (IHL). Many of the foundational obligations governing the conduct of hostilities tend to “individualize” legal assessments – for instance, by focusing on the incidental harm and military advantage associated with particular attacks, and on protections in concrete military operations. Yet the reality of conflict’s impact on human minds is more complex, stretching far in time and space and resisting neat categorization in isolated incidents. Here lies the concern at the heart of the present article. The following sections examine whether, and if so, how, existing IHL protects civilians from cumulative mental harm – that is, mental harm that originates from multiple isolated or entwined sources, be they a direct or indirect effect of (lawful or unlawful) military operations. In so doing, the aim of this article is to move beyond the bias towards individualized, fragmented assessments in IHL to determine the extent to which existing obligations protect against mental harm originating from a multitude of (lawful or unlawful) individual events. Absence of clarity over the law’s protection against such harm has direct bearing on prospects of reparation, acknowledgment of responsibility and cessation of conduct contributing to cumulative mental harm.
The article proceeds in three steps. First, it theorizes the concept of “cumulative mental harm” and discusses the state of the literature at the intersection of mental health protection and cumulation of harm in armed conflict. Second, it analyzes three possible legal avenues for grounding protection from such harm under IHL: (1) the general protection of civilians from the dangers of military operations, (2) the obligation to take constant care to spare civilians in the conduct of military operations, and (3) the prohibition against launching attacks expected to cause excessive incidental civilian harm. Third, in analyzing these three legal avenues under IHL, the article suggests interpretations of existing IHL that would operationalize protections against cumulative mental harm.
Conceptualizing “cumulative mental harm”
To assess the legal protections against cumulative mental harm under IHL, it is first necessary to define the parameters of the concept for the purposes of the present analysis. To begin with, there are no universally agreed definitions of either “mental harm” or “cumulative harm”. Moreover, both the notions of “mental harm” and “cumulative harm” are capable of wide-ranging interpretations, encompassing a broad array of conditions, processes and consequences. In light of this, the demarcations proposed here are made solely for the purposes of the present article, and without prejudice to wider or narrower interpretations of the terms in other contexts and for other purposes.
Mental harm, as understood here, means an adverse impact on a person’s mental health. Anxiety, depression, post-traumatic stress disorder (PTSD) and acute stress disorder are all examples of mental harm. While the concept of mental harm can be conceptualized as a broad category, it bears emphasizing that specific obligations under IHL can operate with thresholds for the types of mental harm that fall within their purview; this can be explained by the very context of armed conflict, which inevitably gives rise to feelings of fear and anxiety. Because of this, the literature on IHL often refers to mental health disorders as a specific form of mental harm. Mental health disorders are characterized by “a clinically significant disturbance in an individual’s cognition, emotional regulation, or behaviour, which is usually associated with distress or impairment in important areas of functioning”.Footnote 11 Examples of such disorders are PTSD, schizophrenia, depression, adjustment and anxiety disorders; these are disorders capable of diagnosis, and which are separate from a general sense of fear or apprehension related to armed conflict. Admittedly, the conceptualization of mental harm as linked to a mental health disorder capable of diagnosis is not the only way to understand mental harm,Footnote 12 and it may risk imposing a hegemonic understanding of such harm that is at odds with the relevant socio-cultural and economic circumstances.Footnote 13 That said, a focus on mental health disorders as a form of mental harm can be a first step towards establishing the relevance of mental harm to IHL obligations and the foreseeability of such harm based on prior studies of trauma.
Cumulative harm, on the other hand, captures harms that are caused by a cumulation of factors or events, rather than from a single, identifiable cause. For instance, PTSD could result from a single traumatic event (for instance, an act of sexual violence), but could equally be caused by a sequence of events. In situations of armed conflict, such a sequence could be caused by various types of belligerent action: a series of attacks in a given area, for instance, can generate escalating fear and anxiety among those present, ultimately leading to mental health disorders within the affected population. Such disorders may also be caused by other sequences, such as when individuals are compelled to relocate in order to avoid attacks or because their homes have been destroyed, and during their displacement endure further risks from attacks in their vicinity as well as food insecurity, inadequate shelter and lack of access to medical assistance. The factors causing such cumulative harm can occur simultaneously (for instance, the simultaneous absence of medical aid and food in camps for the internally displaced) or sequentially (for instance, an attack followed by displacement, in turn followed by deprivation, in turn followed by discrimination and marginalization). As a concept, cumulative harm can be virtually unbounded, covering all traumatic events, processes and experiences that occur following an onset event or series of events.
For the purposes of this article, the concept of “cumulative harm” is employed to refer to harms that are the direct or reasonably foreseeable indirect consequence of a cumulation of events and processes related to the military operations of a party to conflict.Footnote 14 The term “military operation” means “all the movements and activities carried out by armed forces related to hostilities”.Footnote 15 More precisely, it “must be construed to mean the movements, manoeuvres and other action taken by the armed forces with a view to fighting”,Footnote 16 and includes not only ground operations but also the establishment of military installations, defensive preparations and fortifications, among others.Footnote 17 The term is thus broader than “attack”,Footnote 18 and it captures activities that are preparatory and otherwise related to fighting. Thus, orders to civilians to leave a particular area, or the closure of aid or other humanitarian centres in view of military action, would be captured by the concept of “military operation”.
Despite the prevalence of mental harm resulting from a cumulation of events in armed conflict, the literature on IHL has so far failed to address the phenomenon comprehensively. Analysis exists only in fragments, in some cases addressing mental harm and IHL, while in others focusing on the cumulation of harm in the use of force in armed conflict. For instance, legal scholars increasingly focus on the IHL protections against conflict-related mental harms. Lieblich,Footnote 19 Schmitt and Highfill,Footnote 20 Solomon,Footnote 21 and Knuckey, Moorehead, McCalley and BrownFootnote 22 have provided analysis of the obligation of parties to conflict to refrain from attacks that may be expected to cause excessive incidental civilian harm, suggesting, in narrower or broader terms, that this should be understood to require consideration of reasonably foreseeable incidental mental harm to civilians. Priddy,Footnote 23 MardiniFootnote 24 and BreiteggerFootnote 25 have examined the relationship between disability law and armed conflict, while Bosi has provided an overview of existing literature and a brief mapping of various legal protections against mental harm in armed conflict.Footnote 26
With regard to cumulative harm, drawing on the Martens Clause, the Trial Chamber of the International Criminal Tribunal for the Former Yugoslavia (ICTY) suggested over a quarter of a century ago that
in case of repeated attacks, all or most of them falling within the grey area between indisputable legality and unlawfulness, it might be warranted to conclude that the cumulative effect of such acts entails that they may not be in keeping with international law.Footnote 27
At the time, this interpretive stance, which was arguably an exercise in progressive development, was thought by some to be out of step with existing law.Footnote 28 More recently, Lubell and Cohen have initiated a conversation not only on the application of IHL and the law on the resort to force to cumulative harms, but also on the limitations of the law and the potential need for further normative development.Footnote 29 Noting that international law “does not sufficiently consider the aggregate impacts of protracted armed conflict on civilian populations” and drawing from “feminist theories of harm and continuums of violence, undergirded by a recognition of the political economy of war as it affects women”, Ní Aoláin too has argued in favour of a progressive development placing attention on cumulative civilian harm.Footnote 30 Hill-Cawthorne has examined the extent to which IHL (and jus ad bellum) accounts for the overall civilian harm accumulated across a conflict, surveying contrasting views on this matter; while acknowledging that the contrary view may not be straightforwardly contra legem, he has nevertheless argued in favour of the view that cumulative civilian harm must be accounted for.Footnote 31
The present article aims to connect the discussions on mental harm and cumulative harm and to explain how their intersection affects the scope of legal protection. It focuses on the law as it is, rather than on arguments regarding progressive development. Accordingly, the following section turns to an analysis under three legal avenues established in IHL that may provide protection to individuals from cumulative mental harm.
Protections against cumulative mental harm in the conduct of hostilities
Protecting civilians from the dangers of military operations
Under Additional Protocol I (AP I), “[t]he civilian population and individual civilians shall enjoy general protection against dangers arising from military operations”.Footnote 32 According to the International Committee of the Red Cross (ICRC) Commentary on AP I, this provision confirms a “principle” of “general protection”.Footnote 33 Without a doubt, the mental health cost of armed conflict, both as an immediate effect of hostilities and in its cumulative and longer-term manifestations, is a danger that arises from military operations. The key legal question here is whether this principle enshrined in AP I has a self-standing regulatory function and, if so, what type of decision-making it requires or proscribes.
To begin with, one may query whether the protection of civilians from the dangers arising from military operations imposes a self-standing obligation on parties to conflict. According to the second sentence of Article 51(1) of AP I, “[t]o give effect to this protection, the following rules, which are additional to other applicable rules of international law, shall be observed in all circumstances”, and the provision outlines, in further paragraphs, specific obligations against, inter alia, indiscriminate attacks and making civilians the object of attack. On the one hand, this can be interpreted to mean that the first sentence of Article 51(1) is meant to postulate a principle without substantive scope and regulatory reach, merely manifested in the specific obligations subsequently established. The language used in the ICRC Commentary to Article 51(1) could be taken as supporting this reading of the provision.Footnote 34 Under this view, the principle would, at most, have interpretative significance for specific obligations under the treaty. On the other hand, it could be argued that the principle outlined in the first sentence of Article 51(1) has independent regulatory significance, giving rise to obligations extending over and beyond those specified in the rules listed in subsequent paragraphs of the article. On the latter view, Article 51(1) requires that the dangers for the civilian population “be reduced to a minimum”,Footnote 35 a more general positive obligation operating alongside other obligations. Little can be gleaned from practice, jurisprudence or academic writings on this question. Even instruments that do mention this provision do so in an equivocal way – for instance, the Political Declaration on Strengthening the Protection of Civilians from the Humanitarian Consequences Arising from the Use of Explosive Weapons in Populated Areas merely recalls “the obligations under International Humanitarian Law related to the general protection of civilians against dangers arising from military operations”.Footnote 36
If the provision contained in the first sentence of Article 51(1) does indeed posit a self-standing general obligation, then the next question is what this general obligation actually requires of parties to conflict. To begin with, it is worth comparing its text to that of Article 58 on passive precautions, which requires parties to “take the other necessary precautions to protect the civilian population, individual civilians and civilian objects under their control against the dangers resulting from military operations”.Footnote 37 This language slightly differs from that found in Article 51(1), which speaks of dangers arising from military operations; while “resulting” may be read to imply a certain standard of causation,Footnote 38 the term “arising” seems broader. Further, it is clear that the drafters were mindful of the psychological impact of military operations at the time of adopting the Protocol. Article 51(2) prohibits “[a]cts or threats of violence the primary purpose of which is to spread terror among the civilian population”Footnote 39 – since the prohibition on terrorizing civilians, which proscribes purposeful conduct to inflict a mental state of terror, is set in one of the rules implementing the principle in Article 51(1), it is only logical to infer that the principle itself extends to mental harm. And finally, the language of Article 51(1) – “dangers arising from military operations” – is generic. It does not relate exclusively to particular dangers that existed at a particular point in time, but can be interpreted dynamically to include emerging dangers in changing conflict landscapes. This use of generic language therefore makes the provision capable of interpretative extension to dangers of military operations as they evolve through time.Footnote 40 Such an interpretation would comport with the object and purpose of AP I, which is anchored in the continuous and meaningful protection of civilians.Footnote 41
If one were to adopt the view that the principle of general protection from the dangers of military operations has a self-standing regulatory function, and that it requires the taking of positive measures to reduce dangers (including those capable of resulting in harm to mental health), this would align IHL to international human rights law (IHRL).Footnote 42 Of course, IHL and IHRL are two separate legal frameworks, and although they must, to the extent possible,Footnote 43 be read harmoniously, they need not mirror one another. As acknowledged by the International Court of Justice (ICJ), “[s]ome rights may be exclusively matters of international humanitarian law; others may be exclusively matters of human rights law; yet others may concern both these branches of international law”.Footnote 44 That being said, relevant and applicable rules of IHRL bear on the interpretation of rules under IHL, and there are insights to be drawn from the comparison between human rights and a general obligation to protect civilians from the dangers of military operations.
Protections under IHRL do not cease in times of armed conflict,Footnote 45 and human minds are protected from harm under, inter alia, the right to health, recognized, notably, in the International Covenant on Economic, Social and Cultural Rights.Footnote 46 Health, according to the WHO Constitution, is “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”.Footnote 47 Protections of health logically extend to “the underlying determinants of health, such as access to safe and potable water and adequate sanitation, an adequate supply of safe food, nutrition and housing, [and] healthy occupational and environmental conditions”.Footnote 48 States have an obligation to respect, protect and fulfil the right to health, including through immediate steps towards its full realization, and to ensure non-discrimination, with a presumption against the taking of retrogressive steps.Footnote 49 The fact of armed conflict may affect the feasibility of certain measures to protect mental health, but does not displace the right to health of individuals under a State’s jurisdiction.Footnote 50
The right to health covers mental healthFootnote 51 and acknowledges the effect of cumulative conditions that lead to health impacts.Footnote 52 It requires the taking of positive measures to protect individuals. Similarly, one can argue that through the operation of Article 51(1), if understood to entail a self-standing general obligation, parties to conflict must take measures to protect civilians from the dangers of military operations capable of impacting their mental health. The present authors submit that, at the very least, this would mandate acquiring the capacity to assess the potential mental health harms of military operations, and making efforts to consider how military operations can cumulate to create or exacerbate such harms. It must be emphasized that even if the provision of Article 51(1) is not accepted as establishing a self-standing obligation, an obligation to take similar measures to the ones envisioned here would in any event also arise under the duty of constant care in Article 57(1) of AP I and customary law, as analyzed in the following section.
Constant care
As part of a broader effort to “diminish the evils of war as far as military requirements permit”,Footnote 53 and as a supplement to other rules aimed at protecting the civilian population and civilian objects,Footnote 54 IHL requires parties to an armed conflict to take precautionary measures.Footnote 55 While many of the requisite precautions relate specifically to attacks, IHL also contains a more general provision – codified in Article 57(1) of AP I, which is reflective of customary international law – providing that “[i]n the conduct of military operations, constant care shall be taken to spare the civilian population, civilians and civilian objects”.Footnote 56
As with the principle laid down in Article 51(1) of AP I, some might take the view that Article 57(1) does not in fact establish a self-standing obligation, and that it instead merely enunciates a general principle whose practical application is then subsumed in the more concrete rules on precautions in attack codified in the remaining subsections of Article 57.Footnote 57 However, this view is objectionable on a number of grounds.Footnote 58 First, the word “shall” in Article 57(1) indicates that it is a prescriptive provision imposing a duty.Footnote 59 Second, pursuant to the principle of effectiveness (effet utile), treaty provisions must be interpreted so that each has meaning and effect, and Article 57(1) should therefore not be construed in a manner that renders it devoid of independent normative force.Footnote 60 Third, and relatedly, the view that Article 57(1) establishes obligations beyond those specified in the remainder of Article 57 better accords with the object and purpose of AP I as it obliges belligerents to strive to reduce civilian harm arising from all aspects of their military operations, thereby closing a protection gap that would arise if such precautions were required only with respect to the harmful effects of individual attacks.Footnote 61
Based on the ordinary meaning of the terms it employs, and following other authors, it is contended here that the duty affirmed in Article 57(1) of AP I is “general, broad, and flexible”.Footnote 62 The general and wide-ranging nature of the duty can be deduced first from the opening words of the provision explicitly indicating that it applies to “military operations” in general and not merely to attacks.Footnote 63 While the term “constant care” is not defined in IHL, the adjective “constant” clearly implies that the duty is not subject to temporal limitations and applies at all times.Footnote 64 Rather than listing specific types of harm that should be mitigated, the provision contains an open-ended injunction “to spare” civilians. The plain meaning of this directive, certainly when read in light of the protective object and purpose of AP I, suggests that belligerents must constantly strive to spare civilians from any harm that might be caused by their military operations in armed conflict. Indeed, it has been argued that the provision “should be taken literally: total avoidance of damage to the civilian population is the standard that combatants should seek to achieve in all cases”.Footnote 65 This reading aligns well with the UN General Assembly’s affirmation that “[i]n the conduct of military operations, every effort should be made to spare civilian populations from the ravages of war, and all necessary precautions should be taken to avoid injury, loss or damage to civilian populations”.Footnote 66 Further indication that the “ravages of war” from which IHL seeks to spare civilians encompass a wide range of dangers has been deduced from the language of Article 58 of AP I concerning precautions against the effects of attacks, which calls for precautions “against the dangers resulting from military operations”.Footnote 67
The present authors submit that the “ravages”, “dangers” and “injury, loss or damage” from which parties to conflict must constantly endeavour to spare civilians pursuant to Article 57(1) of AP I and the related rule of customary international law should be understood to extend beyond physical harm and encompass mental harm.Footnote 68 It is further submitted that “[c]onstant care requires situational awareness of the violence and harm that has befallen the civilian population before another operation or attack is commenced”Footnote 69 – that is, that the general injunction to spare civilians from harm mandates that parties to an armed conflict attend to the cumulative harmful effects of their actions, including any cumulative mental harm they cause, and constantly seek to avoid or mitigate them.
While serving to establish a broad obligation to seek the total avoidance of civilian harm at all times and in all military operations, the term “constant care” also serves to circumscribe the scope of the obligation. Referring to required conduct rather than a mandated outcome, this wording indicates that the obligation is an obligation of means, not result. It obliges parties to conflict to do everything that can reasonably be expected of them under the circumstances ruling at the time to avert civilian harm. Accordingly, the duty of constant care has been characterized as “a positive and continuous obligation aimed at risk mitigation and harm prevention and the fulfillment of which requires the exercise of due diligence”.Footnote 70 Similarly, it has been contended that the duty of constant care imposes a “clear and simple” demand to, “whenever operationally feasible, take measures designed to mitigate risk to civilians and civilian property”,Footnote 71 and that “the commander will have to bear in mind the effect on the civilian population of what he is planning to do and take steps to reduce that effect as much as possible”.Footnote 72
The flexibility of the duty to take precautions stems on the one hand from the temporally unlimited and otherwise broad injunction that it imposes on the parties to an armed conflict, and on the other hand from the wide margin of discretion that it leaves them to determine what is reasonably possible under the prevailing circumstances.Footnote 73 These contrasting forms of flexibility carry corresponding positive and negative implications for the purpose of averting cumulative mental harm. As submitted, the breadth of the injunction lends credit to the view that parties to conflict have a legal duty to mitigate such harm. Conversely, the wide discretion that the parties have at their disposal raises concern that even if such a duty were to be recognized in principle, it would have limited practical import.
Even a good-faith assessment of what is reasonably possible under the circumstances may limit the extent to which belligerents will be required to mitigate cumulative mental harm. Certain levels of mental anguish among civilians, such as fear, anxiety and apprehension, are an inevitable feature of situations of armed conflict, especially when hostilities occur in proximity to the civilian population, and it would not be reasonably possible for belligerents to fully spare civilians from such harm. At the same time, the duty of constant care should be understood as requiring parties to conflict to seek to avoid or at least minimize, to the extent possible, such mental harm, especially with respect to military operations that are expected to cause mental harm of a particularly traumatizing, disruptive and pernicious nature.
The scope of the obligation to spare civilians from mental harm may be further limited because of practical difficulties in anticipating it. Indeed, while it is generally relatively straightforward to predict physical harm resulting from military operations undertaken in physical space, it may not always be reasonably possible to foresee how such operations will affect people’s mental well-being. The practical difficulties associated with anticipating harm to civilians (especially mental harm), and thus with taking steps to avoid it, will of course only be compounded when the assessment concerns the cumulative effect of multiple actions as opposed to an individual act.
While there are thus reasons for concern that parties to conflict will take advantage of the wide margin of discretion that they have in implementing their duty of constant care to effectively sidestep the obligation, at least when it comes to cumulative mental harm, there are also considerations that serve to temper such concerns. As the Trial Chamber of the ICTY has observed, the Martens Clause enjoins reference to the “principles of humanity” and to the “dictates of public conscience” whenever interpreting a rule of IHL that “is not sufficiently rigorous or precise”.Footnote 74 Accordingly, the Trial Chamber asserted that
the prescriptions of Articles 57 and 58 [of AP I] (and of the corresponding customary rules) must be interpreted so as to construe as narrowly as possible the discretionary power to attack belligerents and, by the same token, so as to expand the protection accorded to civilians.Footnote 75
In line with the interpretive approach thus prescribed, the duty of constant care must be understood to mandate that parties to conflict take concrete positive steps to implement their obligation to spare civilians from harm, including cumulative mental harm. Accordingly, it is posited here that the parties must, at the very least, establish a framework to ensure that any members of their personnel involved in military operations are duly instructed and trained to take constant care to avert such harm and that guidelines are set in place to that end. Among other things, such guidelines should instruct those responsible for implementing military operations on specific measures that they must implement to assess the possible harmful implications of such operations – including the cumulative implications of various elements that they entail – for the physical and mental well-being of the civilian population. The guidelines should further specify how the findings of such assessments should be used to inform the subsequent planning and implementation of the operation, notably in the choice of means and methods of warfare, with a view to averting civilian harm, including cumulative civilian harm, to the fullest extent reasonably possible. Importantly, such instruction, training and guidelines must take into account the context-specific likelihood of particular types of harm, including mental harm.Footnote 76
Since the duty is “constant”, measures to spare civilians must be undertaken throughout the entire cycle of the armed conflict (and arguably even during peacetime preparations), from the training of troops through to the planning of the operation and in assessments conducted during and after completion of the operation. In implementing these measures, the parties will still benefit from a considerable margin of discretion as they assess what is feasible or reasonably possible under the circumstances. That said, a party that fails to set in place any meaningful framework or guidelines for sparing civilians from cumulative mental harm could clearly not be said to be taking constant care to avert such harm. There is, therefore, a twofold duty encompassed under constant care: first, to establish an internal infrastructure that enables assessment of cumulative mental harm, and second, to implement that internal capacity in specific military operations.
Proportionality
Pursuant to the principle of proportionality, established both in treaty law and customary international law,Footnote 77 parties to conflict must refrain from “an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated”.Footnote 78 Two key questions arise in the application of this obligation to cumulative mental harms. First, does the obligation apply to mental harm? Second, if it does, how far does its protection reach? In other words, mental harms of what temporal, geographical and causal proximity fall within its scope?
Mental harm as “injury”
Whether conflict-related mental harm can be addressed through the principle of proportionality is a matter of treaty interpretation for the provision in Article 51 of AP I,Footnote 79 and a matter of customary law identification for its customary equivalent.Footnote 80 What matters here is whether the term “injury” used in Article 51, and accepted as part of the customary rule, can be interpreted to cover not only physical harm but also forms of mental harm.
As a matter of semantics, the ordinary meaning of the term “injury” is “hurt or loss caused to or sustained by a person or thing; harm, detriment, damage”.Footnote 81 The term is therefore capable of accommodating a wide variety of harms, of both a physical and mental nature. What matters for the purposes of interpreting AP I, however, is how its drafters understood “injury”, both at the time of drafting and in the term’s capacity to evolve through time. Neither the discussions at the Diplomatic Conference leading to the adoption of AP I nor the ICRC Commentary on Article 51 address – let alone resolve – this question, but importantly, they do not suggest any restriction of the term to physical harms.
What seems clear is that the drafters of AP I intended the treaty to be of long-lasting relevance. The use of the generic term “injury” suggests that the provision in question was drafted in a way capable of accommodating change through time via evolutionary interpretation,Footnote 82 but how a term evolves is a more complex question. In this regard, Courts have looked at societal understandings and particular trends in the practice of States.Footnote 83 While there is limited practice of States on the question of mental harm under the principle of proportionality,Footnote 84 societies have come to understand injury more broadly, and to include mental harms in its definition. This is particularly obvious in the treatment of injury as it relates to the experience of veterans.Footnote 85 Further, the context of AP I confirms a view that “injury” is not to be limited to physical harms. The concept of “injury” is also dealt with in Article 85 of AP I, the provision on the repression of grave breaches. Under this provision, a set of violations under IHL, when committed wilfully and causing death or serious injury to body and health, trigger special repressive duties for the parties.Footnote 86 Of particular note is the reference to “injury to body and health” (emphasis added), which seems to extend the scope of the term beyond pure bodily harm. And finally, some have argued that this extended interpretation of the term is supported by the object and purpose of AP I.Footnote 87
In the literature, “injury” has typically been associated with physical harms, such as burns, blindness or loss of limbs.Footnote 88 In recent years, however, academics have put forward a number of interpretations of this provision that tie it more closely to mental harms. Schmitt and Highfill, for instance, state that
cognitive or psychological conditions should be understood to be encompassed within the “incidental injury” when they are caused by physical brain trauma, which undeniably qualifies as incidental injury for the purpose of the rule of proportionality when suffered by a civilian.Footnote 89
In tying such cognitive and psychological conditions to the occurrence of traumatic brain injury, they exclude harm that is purely psychological in nature.Footnote 90 Others disagree with such an exclusion: Lieblich, relying on a textual and teleological interpretation of Article 51, advances the argument that even stand-alone mental harm can qualify as “injury” under the provision.Footnote 91 A similar argument is made by Knuckey, Moorehead, McCalley and Brown, who accept that serious and long-term harm to mental health following exposure to a traumatic event qualifies as “injury”.Footnote 92 More and more, we see authors whose views favour the inclusion of mental harms under the term “injury” in the rule of proportionality.Footnote 93
Thus, the IHL obligation to abstain from disproportionate attacks provides no cogent reasons to restrict the interpretation of “injury” to physical harms only. That it is not so confined does not mean that it covers all forms of impact on mental health, however; if “injury” were to be equated with any mental harm, including the experience of fear and intimidation intrinsic to conflict, this reading may constrain virtually all attacks against lawful targets that occur in the vicinity of civilians. Given this, authors have sought to constrain the application of the rule to impacts on mental health of a particular severity, such as PTSD and other mental health disorders. While it is not the intention of this article to set a precise boundary of relevant mental harm, it agrees with existing literature that the rule should, first, exclude general feelings of fear, and second, lend itself to capturing mental harms of a particular severity. The law can begin to operate with certain categories of mental harm deemed “injurious”, either because the cognitive and psychological conditions are the result of specific physical effects,Footnote 94 or because of the crossing of a severity lineFootnote 95 (for instance, PTSD as a result of experiencing – including by witnessing – an attack).Footnote 96
Reasonably foreseeable cumulating causes of mental harm
Parties to conflict are not required to consider every civilian harm consequent to an attack in their proportionality assessments; rather, they are required to make decisions on the basis of “expected” incidental civilian harm. This expectation has been interpreted to cover “reasonably foreseeable” civilian harm.Footnote 97 The use of the phrase “may be expected” in Article 51(5)(b) of AP I clarifies that the inquiry is not into whether the attacker foresaw the harm, but whether the harm was foreseeable to a reasonable person in the circumstances of the attacker.Footnote 98
All relevant effects that are foreseeable, both direct and reverberating, are covered by Article 51(5)(b) and must guide the decision-making of the party to conflict.Footnote 99 While the direct effects of attacks, at least in the kinetic context, typically involve death, injury and destruction of property, and directly follow the point of impact, reverberating effects cover a wider range of impacts that may be temporally and geographically distant from the attack. Thus, the reverberating effects of an attack can manifest in a number of steps. Gillard provides an example of attack which “damages an object providing vital services to the civilian population, such as an electricity generation and distribution system, which in turn prevents water purification systems from operating, leading to an outbreak of waterborne diseases among the civilian population”.Footnote 100
If these harms are reasonably foreseeable, they should be included in the act of weighing harm against military advantage. Foreseeability will depend, among other factors, on the type and context of the attack,Footnote 101 its location, and the weapons used.Footnote 102 Importantly, foreseeability would depend on the population affected by the attack – certain populations would be more susceptible to mental harm, given their particular vulnerability (for instance, if they have been subjected to long-term conflict, or a conflict of a particular intensity, or have been displaced or malnourished). Even if the vulnerability of the civilian population, and thereby its higher likelihood of suffering from mental harm, is the consequence of a prior lawful attack (or attacks), the party to the conflict must factor in this vulnerability when making a proportionality assessment.
Importantly for the purposes of compliance with their obligation of proportionality, parties to a conflict must be equipped with the tools and knowledge to assess the types of incidental civilian harms they ought to reasonably foresee under the rule. If the rule requires consideration of relevant mental harms, then logic dictates that parties to conflict must possess the capacity to engage in such consideration. Applied to the context of cumulative mental harms, this means that parties to conflict must, inter alia, develop an understanding of the sources of mental harm in armed conflict; plan their operations in ways that would minimize the risk of such harm; acquire sufficient knowledge of the particular vulnerabilities of a civilian population that would make it more likely to suffer such mental harm; and consider the impact of context on the manifestation of mental harm. Admittedly, it may be difficult to causally tie a particular attack to a particular mental harm manifesting in a particular individual, but establishing a connection between attacks and relevant mental harms is not impossible. For instance, statistical analysis of the prevalence of mental disorders in a population could allow parties to conflict to understand how their attacks might create or exacerbate harmful mental health conditions in that population.
As noted, the sequence of events causing cumulative mental harm during an armed conflict will not necessarily consist only of attacks. Relocation directives causing mass displacement of civilians, for instance, may cause or contribute towards mental harm.Footnote 103 Even if the rule of proportionality established in Article 51(5)(b) of AP I cannot extend to harms caused within operations wider than individual attacks, some have argued that a broader general principle of proportionality constrains the behaviour of parties to conflict. Under this view, proportionality is a general principle of law in the meaning of Article 38(1) of the Statute of the ICJ, which requires an equitable balance between competing legal interests for all conduct of parties to conflict (not limited to attacks).Footnote 104 The conventional and customary rules on proportionality in attack represent, according to this argument, a concrete manifestation of this general principle of law in IHL; however, it has been posited that these rules “do not exhaust the normative content of proportionality as a general principle of the law of armed conflict”.Footnote 105 On the view that proportionality is a general principle of law, it could be argued that the incidental civilian harm assessment under proportionality as a general principle of IHL reaches beyond the harmful effects of attacks to encompass civilian harm, including cumulative mental harm, caused by other activities undertaken in military operations. While the present article does not take a position on the viability of this line of argument, it bears emphasizing that protections under this claimed principle could arguably be covered, at least in part, by the duty of constant care under Article 57(1) of AP I and customary law: a party to conflict cannot discharge its proportionality duties unless it has secured an internal assessment capacity and put that capacity to practice in its battlefield conduct.
Conclusion
Civilian harms arising from armed conflict are neither confined to the physical realm nor uniquely caused by singular, isolated events. Reporting from armed conflicts strongly suggests that civilians are left with mental scars – in the form of PTSD, depression and other disorders – as a consequence of multiple isolated or interrelated actions undertaken during military operations which, taken individually, may have been lawful. What this article has sought to demonstrate is that, first, human minds are protected from harm under existing IHL, and second, despite the many legally mandated individualized assessments of attacks, the law is also capable of capturing harms that emerge during and from a cumulation of events in the course of military operations.
Given the practical difficulties in foreseeing precise forms of mental harm and their relation to conduct in military operations, the most important question is one of meaningful operationalization of existing protections. A core argument of this article is that to comply with the law, parties to conflict must ensure a baseline capacity to understand, assess and mitigate mental harms likely to arise from military operations. This baseline capacity would require work with psychologists and psychiatrists, and training of the relevant military personnel. Further, it will come into play at different stages of actual hostilities, sometimes requiring the taking of positive measures to limit the risk of cumulative mental harm, and sometimes even requiring parties to refrain from particular attacks.
Addressing cumulative mental harm is not an operational impossibility, and the occurrence of such harm is not an inevitability of armed conflict. With advances in our understanding of the human mind, and with better and more comprehensive reporting from armed conflicts, it becomes easier to appreciate the extent and severity of cumulative mental harms suffered by civilian populations. Properly understood and construed, IHL does and must provide protection from such harms for the civilian population.
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