Introduction
During armed conflict, the use of explosive weapons with wide area effectsFootnote 1 in populated areasFootnote 2 has a devastating impact on civilians. Most visible are the direct blast and fragmentation effects of explosive weapons, which kill and injure civilians and damage civilian objects including civilian houses. Less visible, but equally devastating, are the reverberating effects of the use of explosive weapons in populated areas, meaning those effects “that are not directly and immediately caused by the attack, but are nevertheless the product thereof”.Footnote 3 When civilian housing and essential infrastructure are damaged or destroyed, civilians are affected in a number of ways, especially when populated areas sustain attacks over a long period of time.Footnote 4 Civilians may be displaced, electricity may be temporarily or permanently disabled, health services may be weakened, wastewater collection and treatment may be reduced, and the accessibility, quality and quantity of water supplies may deteriorate.Footnote 5 In many contexts, the reverberating effects of an attack, particularly one that disables the national electricity system, may far outweigh the immediate civilian casualties caused by the attack.Footnote 6
While international debate concerning the legal obligation to take into account the reverberating effects of an attack has evolved significantly over the last ten years – most recently in the context of cyber-warfareFootnote 7 – and enjoys increasing acceptance by commentatorsFootnote 8 and States,Footnote 9 there is still no consensus on the scope of this obligation as it applies to the rules on proportionality and precautions in attack.Footnote 10 This article seeks to shed light on this grey area in the law, particularly as it relates to the use of explosive weapons in populated areas. More precisely, the article examines the parameters of the obligation under the rules on proportionality and precautions in attack, including the extent of reverberating effects that must be taken into account, how reverberating effects should be evaluated, and how such effects must be avoided or minimized. While the use of explosive weapons in populated areas is not explicitly prohibited under international humanitarian law (IHL), this article will demonstrate that such use might violate the rule on proportionality and certain precautionary requirements, if the reasonably foreseeable reverberating effects of the attack are not taken into account.Footnote 11
The article is structured in four parts. The first part presents the IHL rules on the conduct of hostilities, while the second part explores the legal arguments in support of the position that foreseeable reverberating effects must be taken into account for the purposes of the rule on proportionality and some of the rules relating to precautions in attack. The third part examines the scope of the obligation to take into consideration foreseeable reverberating effects, including the notion of “foreseeability” and the standard of care imposed by the obligation. The article concludes by analyzing the practical measures that must be taken to assess and minimize the foreseeable reverberating effects of an attack, as required by the obligation to take all feasible precautions in attack.
IHL rules on the conduct of hostilities
Like other means of warfare, the use of explosive weapons in populated areas is regulated by IHL rules on the conduct of hostilities, namely, the rules on distinction, proportionality and precautions in attack. These rules, as set out in treaty and customary IHL, are applicable in both international and non-international armed conflicts.Footnote 12
The rule of distinction prescribes that parties to an armed conflict must at all times distinguish between civilians and civilian objects on the one hand, and military objectives on the other;Footnote 13 civilians and civilian objects are protected and must not be the object of attack.Footnote 14 The prohibition on indiscriminate attacks which flows from the rule of distinction prohibits attacks not directed at a specific military objective, attacks which employ means or methods of combat that cannot be directed at a specific military objective, and attacks which employ means or methods of combat the effects of which cannot be limited as required by IHL and consequently, in each such case, are of a nature to strike military objectives and civilians or civilian objects without distinction.Footnote 15 The prohibition of indiscriminate attacks also entails the prohibition of disproportionate attacks.Footnote 16 According to this prohibition, the expected incidental loss of civilian life, injury to civilians and damage to civilian objects, or combination thereof (hereafter referred to as “incidental damage”), of an attack must not be excessive in relation to the concrete and direct military advantage anticipated.Footnote 17 While it is argued that an object which serves both civilian and military functions (“dual-use object”) is to be regarded as a military objective in its entirety,Footnote 18 there is considerable support from StatesFootnote 19 and commentatorsFootnote 20 for the idea that
the destruction of the civilian part of this object, or more generally, the fact that the attack puts an end to its use by civilians, as well as the reverberating effects of such damage forms part of the incidental damage that must be taken into account under the proportionality principle.Footnote 21
In order to ensure compliance with the rules of distinction and proportionality, and to ensure that constant care is taken in the conduct of military operations to spare civilians and civilian objects, IHL requires parties to an armed conflict to take precautions in attack. Precautionary requirements entail doing everything feasible to verify that the target is a military objective;Footnote 22 taking all feasible precautions in the choice of means and methods of attack, with a view to avoiding, and in any event minimizing, the expected incidental damage;Footnote 23 refraining from launching an attack that may be expected to violate the rule on proportionality;Footnote 24 and cancelling or suspending an attack if it becomes apparent that the target is not a military objective or is subject to special protection, alternatively, that the attack may be expected to violate the rule on proportionality.Footnote 25 The application of these rules, which are the most relevant ones in relation to the use of explosive weapons in populated areas, will necessarily be based on ex ante informationFootnote 26 – that is, the information that is reasonably available to the attacking party at the time of the attack – and not on hindsight.Footnote 27
As is clear from the elaboration of these basic conduct of hostilities rules, both the rule of proportionality and several of the precautionary rules require an assessment of the expected incidental damage arising from an attack.Footnote 28 While many military manuals include the notion of incidental damage, the term has been defined in different ways.Footnote 29 At its core, it refers to damage to civilians and civilian objects that is incidental, collateral or secondary to an attack against a lawful target. In the view of the International Committee of the Red Cross (ICRC) and others, incidental damage also includes the foreseeable reverberating effects of an attack,Footnote 30 otherwise known as “knock-on” or “indirect” effects.Footnote 31 According to this position, commanders are not only obliged to take into account the direct incidental damage that may be expected from an attack, but must also consider the foreseeable reverberating effects of the attack. These effects form part of the incidental damage that must be weighed up against the anticipated military advantage under the rules of proportionality and precautions in attack, and which must be taken into consideration when taking all feasible precautions in the choice of means and methods of an attack in order to avoid, and in any event minimize, the expected incidental damage.
Legal obligations regarding the reverberating effects of an attack
The legal obligation to take into account the reverberating effects of an attack derives from rules in Additional Protocol I (AP I) on proportionality and precautions, interpreted in line with the rules on treaty interpretation. In addition, there is a growing body of State practice which demonstrates increasing acceptance of this obligation.
Treaty interpretation
As with all treaty rules, the AP I rules on proportionality and precautions in attack must be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context, and in light of the object and purpose of the treaty.Footnote 32 In this regard, there are a number of arguments to support the view that the “expected” incidental damage to civilians should be interpreted so as to include the reverberating effects of an attack.
Textual interpretation
First, the phrase “may be expected” in Articles 51(5)(b) and 57(2)(a)(iii) and (b) of AP I is not explicitly limited in either time or space. Indeed, the 1974–77 Diplomatic Conference expressly rejected attempts to confine incidental damage to those in the immediate vicinity of the military objective.Footnote 33 There is accordingly no reason, based on the text of the provisions, to limit the assessment under the rules on proportionality and precautions in attack to the immediate or direct effects of an attack. This argument is articulated by Droege, who states that “considering the wording of Article 51(5)(b) of Additional Protocol I (‘may be expected’), it is reasonable to argue that foreseeable damages, even if they are long-term, second-and third-tier damages, must be taken into account”.Footnote 34 Similarly, Sassòli and Cameron take the view that
the expected collateral damage from an attack on a dual-use object … must include the damage expected due to the destruction of the object itself, in addition to whatever other collateral damage that may be expected in the surrounding area or that is foreseeable, including through reverberating effects.Footnote 35
This approach is consistent with the ordinary meaning of “expected”, which is defined in the Oxford English Dictionary as “regard[ed] that something is likely to happen”.Footnote 36
Purposive interpretation
Second, the rules on proportionality and precautions in attack must be interpreted in light of their context, including the headings and the respective chapeau provisions of Articles 51 and 57 of AP I. Indeed, AP I Article 51(5)(b) on proportionality should be read in light of the heading of Article 51 (“Protection of the Civilian Population”) as well as Article 51(1), which provides that the civilian population and individual civilians “shall enjoy general protection against dangers arising from military operations”.Footnote 37 Likewise, the specific rules on precautions in attack operate under the umbrella of AP I Article 57(1), which provides that “in the conduct of military operations, constant care shall be taken to spare the civilian population, civilians and civilian objects”.Footnote 38 It is true that the humanitarian objective of the rule on proportionality is explicitly tempered by military considerations (for instance, by only prohibiting “excessive” incidental damage compared to the concrete and direct military advantage) and that the rules on precautions in attack are contingent upon what is reasonably feasible. However, “incidental damage” as such – separate from the subsequent proportionality assessment or considerations of feasibility – should arguably be interpreted in light of the humanitarian purpose spelled out in the chapeau provisions, so as to provide the broadest protection to civilians, including by requiring that commanders take into account the foreseeable reverberating effects of an attack.
Moreover, the relevance of reverberating effects is affirmed in other articles of AP I, including Articles 54(2) and 56(1), which prohibit attacks on specially protected objects (objects indispensable to the survival of the civilian population and works or installations containing dangerous forces), arguably because of the foreseeable humanitarian impact if such objects are damaged or destroyed.Footnote 39
State practice
The rules on treaty interpretation support the view that the notion of “expected” incidental damage as set out in AP I entails an obligation to take into account the reverberating effects of an attack. Increasingly, such an approach also enjoys support in State practice. In particular, there is significant State practice arising from the Third Review Conference on the Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects (CCW) in 2006. In the debate concerning Protocol V of the CCW on explosive remnants of war (ERW), several States underlined that the long-term humanitarian impact of ERW for civilians had to be considered as part of the proportionality analysis. For example, Switzerland expressed the view that
the military commander's proportionality assessment with regard to the choice and use of a particular means or method of warfare must also take into account the foreseeable incidental long term effects of an attack such as the humanitarian costs caused by duds becoming ERW.Footnote 40
As a result, the Final Declaration of the Third Review Conference of the CCW in 2006 – adopted by consensus – notes that “the foreseeable effects of explosive remnants of war are a relevant factor to be considered in applying the international humanitarian law rules on proportionality and precautions in attack”.Footnote 41 This position is also reflected in the text of Article 3(10)(a) of Amended Protocol II to the CCW, which provides that circumstances to be taken into account when considering all feasible precautions to protect civilians from the effects of weapons include “the short- and long-term effects of mines upon the local civilian population for the duration of the minefield”. In 2015, at an ICRC Expert Meeting of States on the use of explosive weapons in populated areas, several States also expressed support for the view that commanders must take into account the foreseeable reverberating effects of an attack.Footnote 42
Moreover, in providing guidance on how to apply the rules on proportionality and precautions in attack, several States refer to the “second-order” or “foreseeable” effects of an attack in their military manuals.Footnote 43 For example, the US Army manual Counterinsurgency (US Counterinsurgency Manual) of 2006 indicates that
leaders must consider not only the first-order desired effects of a munition or action, but also possible second and third-order effects – including undesired ones. For example, bombs delivered by fixed-wing close air support may effectively destroy the source of small arms fire from a building in an urban area; however, direct-fire weapons may be more appropriate due to the risk of collateral damage to nearby buildings and non-combatants.Footnote 44
In sum, the interpretation of the AP I rules on proportionality and precautions in attack indicates that the notion of incidental damage is not limited to the direct effects of an attack but encompasses certain reverberating effects, which must be taken into account when assessing the lawfulness of an attack. Although this section has not examined whether the same obligation is inherent in the equivalent customary IHL rules on proportionality and precautions in attack, the growing body of state practice points in that direction – i.e., that they are understood in the same way.
What is the scope of the obligation to take into account the reverberating effects of an attack?
Having shown that the rules on proportionality and precautions in attack encompass an obligation to take into account the reverberating effects of an attack, this section examines the scope of this obligation. What is the necessary degree of causation between the attack and the reverberating effects of the attack, such that those effects must be considered for the purposes of the rules on proportionality and precautions in attack? When can reverberating effects be considered too remote in time or space? Are there certain reverberating effects that are in general objectively foreseeable? With a view to identifying more precisely the parameters of the obligation to take into account the reverberating effects of an attack, it is first necessary to examine the legal standard for causation, including the notion of “foreseeability”. Moreover, this section will explore the temporal, geographical and material scope of the obligation to take into account the foreseeable reverberating effects of an attack.
Defining the causal link
As previously noted, the position of the ICRC and others is that commanders must take into account the foreseeable reverberating effects of an attack.Footnote 45 Practically speaking, it is impossible to foresee all possible reverberating effects of an attack. Thus, a reasonable legal standard must reflect this reality and acknowledge that some reverberating effects are too remote and thereby outside the scope of what must be considered at the time of the attack.Footnote 46 Limiting the causal link through the standard of foreseeability is in line with the approach adopted by States in defining the scope of incidental damage. For example, the Final Declaration of the Third Review Conference of the CCW notes that “the foreseeable effects of explosive remnants of war are a relevant factor to be considered in applying the international humanitarian law rules on proportionality and precautions in attack”.Footnote 47 In addition, several States have explicitly adopted the standard of foreseeability in their military manuals.Footnote 48 Moreover, the Inter-American Commission on Human Rights stated in its report on Colombia in 1999 that the principle of proportionality required that foreseeable injury to civilians and damage to civilian objects should not be disproportionate or excessive to the anticipated concrete and direct military advantage.Footnote 49
Different tests have been proposed to define the requisite causal link for the purpose of the obligation to take into consideration reverberating effects under the rules of proportionality and precautions in attack. For example, in the context of computer network attacks, Schmitt, Harrison Dinnis and Wingfield have suggested a “but for” legal test requiring that the attack must be the “proximate cause” of the effects – i.e., reverberating effects are only relevant to the proportionality assessment and the obligation to take feasible precautions in attack, if such effects would not have occurred “but for” the attack.Footnote 50 In effect, a “but for” test reverses the assessment, such that it is necessary to start by examining the reverberating effect in question and tracing a line of causation back to the attack. Although this approach may be more effective in excluding those effects that are too remote, it would appear more useful for an ex post facto assessment as opposed to a standard that can be easily complied with by commanders in the field.
Another test focuses on the degree of likelihood of the reverberating effects. In this regard, Greenwood argues that in its normal meaning, “a consequence is said to be expected if it is thought more likely than not that the consequence will result. A lesser degree of risk is not sufficient.”Footnote 51 Similarly, the Commentary on the Harvard Humanitarian Policy and Conflict Research Manual on International Law Applicable to Air and Missile Warfare (AMW Manual) takes the view that “expected” (and “anticipated”) “means that the outcome is probable, i.e. more likely than not”.Footnote 52 This approach, however, is based on an overly restrictive interpretation of “expected”. As noted above, the ordinary meaning of “expected” is that something is “likely to occur” rather than “more likely than not”. Even if the risk of incidental damage is only 40% likely (i.e., less likely than not), it is still foreseeable and should be taken into account when applying the rules on proportionality and precautions in attack. Thus, at a 2005 expert meeting convened by the Geneva Academy of International Humanitarian Law and Human Rights, it was argued that the scope of the obligation should be based on the notion of “reasonable causality”, meaning that attackers must take into account “civilians dying of thirst, if there [is] a reasonable expectation of causality or if thirst and certain diseases [are] a likely or foreseeable consequence of the attack”.Footnote 53
Accepting that foreseeability is the most appropriate standard for limiting the scope of the reverberating effects that must be taken into account, it is necessary to examine this standard in greater detail.
Is “foreseeable” a subjective or objective standard?
At one end of the spectrum, it is sometimes argued that the rules on proportionality and precautions in attack inevitably involve a subjective assessment by the military commander responsible for launching the attack. In particular, this view holds that the process of assessing both the concrete and direct military advantage, as well as the expected incidental damage, is based on the subjective view of the military commander in light of his or her specific skills, experience and knowledge, in the circumstances ruling at the time.Footnote 54 In addition, it has been argued that determining whether the expected incidental harm is excessive in relation to the concrete and direct military advantage is also a subjective matter. For example, according to the US Law of War Manual, “the question of whether the expected incidental harm is excessive may be a highly open-ended legal inquiry, and the answer may be subjective and imprecise”.Footnote 55
In contrast to the view that the expected incidental damage and anticipated military advantage should be assessed on an entirely subjective basis, it is argued that the rules on both proportionality and precautions in attack incorporate a degree of objectivity. This is supported by the terms “may be” and “expected” in the relevant provisions, which in conjunction clarify that the relevant standard is not what the commander in fact, subjectively, expected, but what can objectively be predicted. This interpretation finds support in the ICRC Commentary to Article 57 of AP I, which, while recognizing that the rule on precautions in attack includes an element of subjectivity, notes that “the interpretation must above all be a question of common sense and good faith for military commanders”.Footnote 56 In other words, compliance with the rule must also be measured against the objective standards of “common sense” and “good faith for military commanders”.Footnote 57
More recently, the objective element of these rules has been framed as a requirement of reasonableness. For example, Dinstein takes the view that the attacker “must act reasonably and in good faith”.Footnote 58 A similar approach is taken in the 2001 Canadian Manual on the Law of Armed Conflict in relation to the rule on precautions in attack: “The test for determining whether the required standard of care has been met is an objective one: Did the commander, planner or staff officer do what a reasonable person would have done in the circumstances?”Footnote 59 This approach is also adopted by Kalshoven, who indicates that the relevant standard is “that of a normally alert attacker who is reasonably well-informed and who, moreover, makes reasonable use of the available information”.Footnote 60
An objective standard is also reflected in the case law on disproportionate attacks, namely in the Galić case before the International Criminal Tribunal for the former Yugoslavia (ICTY). Here, the Tribunal held that
in determining whether an attack was proportionate it is necessary to examine whether a reasonably well-informed person in the circumstances of the actual perpetrator, making reasonable use of the information available to him or her, could have expected excessive civilian casualties to result from the attack.Footnote 61
While it must be emphasized that IHL and international criminal law (ICL) are distinct bodies of law, the latter is an important source of interpretation of IHL rules.Footnote 62 As argued by Sassòli and Cameron, “any behaviour which leads to individual criminal responsibility must first be contrary to the standard of care required by IHL from belligerent parties”.Footnote 63
A similar but slightly distinct approach is to focus not only on a standard of “reasonable person”, but on the slightly higher standard of “reasonable commander”. According to Cannizzaro, the standard of reasonable commander “on the one hand tends to locate the assessment of proportionality with the subjective situation of the agent, but on the other hand seems to require an objective degree of diligence”.Footnote 64 For example, Sassòli and Cameron argue that
while the average “reasonable person” on the street might not be expected to foresee that destroying electricity facilities would cut off the civilian fresh water supply, the reasonable military commander, who is aware of the interconnectedness of infrastructure, would be expected to foresee this consequence.Footnote 65
The standard of the reasonable commander has been embraced by some States. For example, Israel takes the view that:
the principle of proportionality requires consideration of a commander's assessment of the expected collateral damage from an attack. The test is based on the expected collateral damage that a “reasonable commander” would have assessed at the time of attack – and not the damage that actually occurred as a result of the attack.Footnote 66
In relation to reverberating effects, the standard of the reasonable commander would require that the attacker takes into account the reasonably foreseeable reverberating effects of the attack, meaning those effects that are foreseeable for a reasonable commander, making use of the information that is reasonably available to him or her, and in light of the circumstances ruling at the time, including whether the attack is pre-planned or an attack of opportunity. This is the preferred standard of care as it excludes negligent behaviour that does not meet an objective degree of diligence, whilst clearly taking into account that the rules apply based on the circumstances ruling at the time.
Are some reverberating effects objectively foreseeable?
Acknowledging that “reasonable foreseeability” entails an objective standard enables the identification of certain elements that a reasonable commander should take into account – i.e., which would be unreasonable to ignore – when assessing the expected reverberating effects of an attack. Reverberating effects may be considered reasonably and objectively foreseeable based on past practice and empirical research, lessons learned and publicly available information.
Past practices and empirical data
While recognizing that no two cases are identical, past experiences and empirical data can contribute to making certain reverberating effects foreseeable. For instance, in light of the nuclear attacks on Hiroshima and Nagasaki and the extensive subsequent research exposing the long-term effects of these attacks, it can no longer be argued that reverberating effects of using nuclear weapons – such as long-term health effects – are too remote or speculative.Footnote 67 In the context of the CCW negotiations on Protocol V on ERW, past practice and extensive documentation regarding the failure rates of submunitions provided an important indication of the foreseeable reverberating effects of an attack using such weapons. For example, the ICRC stated that
in light of the experience gained from the use of cluster munitions in past conflicts and the work of governments and organizations to address them, the ICRC is of the view that the application of the proportionality rule must now include the extended impact of submunitions (and other ordnance) that become ERW. When these weapons are used in or near populated areas the long-term consequences of unexploded submunitions upon civilians are readily foreseeable. If civilians are already present in a target area, they will predictably need to gather food and water, travel, seek medical care and conduct other daily activities which put them at risk from unexploded submunitions. If they have left the area during the hostilities, it is predictable that they will return at the earliest opportunity and be at risk from unexploded submunitions.Footnote 68
In effect, “past experience has put users on notice about the long-term dangers that cluster munitions cause to civilians”.Footnote 69 As noted above, past practice was accepted in the context of the CCW as an important source of understanding the objectively foreseeable reverberating effects of certain weapons.Footnote 70
At least Ireland and Norway have made explicit reference to the foreseeable effects of an attack or a particular weapon being informed by past practice. For example, Ireland has noted that military commanders “will be informed in their assessments of likely, post-conflict harm to civilian life and property by – amongst other things – the considerable research into this question that has been done in recent years”.Footnote 71 Similarly, at an ICRC Expert Meeting on the humanitarian, technical, legal and military challenges posed by cluster munitions, a representative from the Norwegian Ministry of Defence expressed the view that
it is difficult to claim that the long-term effects of cluster munitions are too remote or uncertain to be considered by a military commander. Experiences in Vietnam, Laos, and other places have demonstrated both the magnitude of the problem and the length of time required to resolve it.Footnote 72
Past experiences and empirical data have also informed the foreseeable reverberating effects of damage to or destruction of electricity networks. For example, it is estimated (conservatively) that the coalition attacks on Iraq's electrical power system in 1991 resulted in 70,000 civilian deaths.Footnote 73 In effect, the attacks reduced Iraq's power capacity to 15% of its pre-conflict levels, with a significant impact on health services (reduced hospital capacity, inability to refrigerate adequate quantities of vaccines) and sanitation (inability to treat and dispose of raw sewerage).Footnote 74 More recently, statistical analysis has demonstrated that disruption of electricity and safe drinking water can have a dramatic impact on civilian lives and health. For instance, the increase in hepatitis, dysentery and typhoid in certain parts of Syria has been attributed to the reduced access to safe drinking water, sanitation and hygiene in those areas.Footnote 75
In some cases, past experiences, such as the attacks in Iraq, have led to a change in policy. For example, during Operation Allied Force in Kosovo, NATO forces sometimes used carbon graphite filaments designed to temporarily disrupt power. This was in part based on a policy decision to minimize long-term incidental harm to civilians.Footnote 76 In addition, greater awareness in the public domain regarding the interconnectedness of essential services has put commanders on notice regarding the objectively foreseeable reverberating effects of damage to or destruction of essential infrastructure.Footnote 77 For instance, the report of the ICRC Expert Meeting on Explosive Weapons in Populated Areas provides the example that “if the energy supply is cut, the ability to ensure the continuity of the water supply service and the evacuation and treatment of wastewater out of a populated area diminishes”.Footnote 78
Finally, it should be noted that the logic of objectively foreseeable effects is already incorporated into decision-making tools, which are adapted so as to take into account past practices and ensure that lessons learned are incorporated into future targeting assessments. For example, collateral damage estimation methodologies (CDMs) – used by some militaries to estimate the expected collateral damage arising from an attack – rely on testing and data, as well as analysis of past practice and lessons learned through battle damage assessments.Footnote 79 Indeed, the CDM used by the United States joint services notes that “[a]s a science, the CDM uses a mix of empirical data, probability, historical observations, and complex modeling for [collateral damage estimation] analysis”.Footnote 80 States are also required to take into account the foreseeable effects of a particular weapon when carrying out legal reviews of new weapons under Article 36 of AP I.Footnote 81 Given the remoteness from the actual combat situation in which the weapon might be used in the future when carrying out the weapons review, this assessment must be premised on an assessment of the objectively foreseeable effects of the weapon in question.
The context of the attack
The circumstances ruling at the time of the attack will impact what kind of reverberating effects may be objectively foreseeable. With respect to repeated or cumulative attacks, to the extent that the effects of past attacks on a populated area are – or should – reasonably be known, this must also be taken into account for the purpose of respecting the rules on proportionality and precautions in attack.Footnote 82 If a commander is aware that civilian infrastructure has been partially damaged, it is foreseeable that any further incidental damage caused by an attack will increase the reverberating effects on civilians. For example, if an attacker knows that a water treatment plant is only operating at 50% of its capacity due to previous damage, the reverberating effects on civilians caused by further incidental damage to the plant will be more significant than if the treatment plant was fully functioning. This is particularly true if the cumulative attacks take place in a short period of time, as it is then likely that the attacker is aware of the extent of past incidental loss of life, injury and damage.
Moreover, known contextual factors such as economic sanctions, blockades, the protracted nature of a conflict or the inability of engineers to repair essential infrastructure due to denial of access may also be relevant to an assessment of the foreseeable reverberating effects of an attack. For instance, if there are long-term sanctions in place, and it is known that construction material is not accessible or is severely restricted, it is objectively foreseeable that the reverberating effects of an attack are more likely to last longer and be more severe. Similarly, if essential infrastructure cannot be repaired because access to the targeted area is systematically denied (including for engineers), it is reasonably foreseeable that the reverberating effects of an attack which damages essential infrastructure can be expected to have a more significant impact on civilians in the area. Likewise, in protracted conflicts such as those in Syria, eastern Ukraine, Libya or Yemen, it is reasonably foreseeable that the quality of essential services will have declined due to years of neglect or inability (financial or otherwise) to ensure proper maintenance of infrastructure and that the reverberating effects of damage to or destruction of essential civilian infrastructure – meaning the infrastructure which if damaged or destroyed will have a significant impact on essential services – will therefore have a more significant impact on the lives and health of the affected population.Footnote 83
Temporal scope of “foreseeability”
In identifying the scope of the obligation to take into account the reasonably foreseeable reverberating effects of an attack, a lot of attention has been focused on the appropriate temporal scope. In other words, when an attacker is assessing the compliance of an attack in accordance with the rules on proportionality and precautions in attack, how far into the future should he or she consider? Is it necessary to balance the concrete and direct military advantage anticipated against the effects of an attack that are expected to eventuate in the days, months or even years following the attack?
As was demonstrated during the CCW discussions concerning ERW,Footnote 84 there is no clear consensus on this question. On the one hand, it has been argued that the time frame of the “expected effects” of an attack should be limited, as long-term effects are too remote. For example, in 2002, Greenwood suggested that it is only the “immediate risk” (i.e., during the attack and in the hours immediately after the attack) from ERW that should be considered in the proportionality equation, because the “long-term risk” posed by ERW “turns on too many factors which are incapable of assessment at the time of the attack”.Footnote 85 According to Greenwood, such factors include “when and whether civilians will be permitted to return to an area, what steps the party controlling that area will have taken to clear unexploded ordnance, [and] what priority that party gives to the protection of civilians”.Footnote 86 At least two States at the CCW supported this view.Footnote 87 Similarly, Kenneth Rizer expressed the view in 2001 that “open-ended consideration of indirect effects is … troubling” as it “opens up a Pandora's box of other problems”, particularly the impossibility of defining a precise temporal limit for when indirect effects can be considered as too remote.Footnote 88 Ultimately, this line of argument seeks to remove the challenges posed by an unknown number of intervening factors by drawing a neat cut-off point after the “immediate” effects of an attack.
In contrast to this approach, a number of States and commentators have argued that the long-term effects of an attack are indeed relevant to the rules on proportionality and precautions in attack. At the CCW, a number of states including Brazil,Footnote 89 the Czech Republic,Footnote 90 Norway,Footnote 91 Sweden,Footnote 92 SwitzerlandFootnote 93 and IrelandFootnote 94 expressed the view that the “long-term” effects of ERW must be taken into account when complying with the rule on proportionality in attack.Footnote 95 Additionally, Austria indicated that the “subsequent effects” of ERW must also be considered as part of the obligation to take all feasible precautions in attack.Footnote 96 In particular, New Zealand questioned the “immediate effects” standard, noting that this was an arbitrary measurement: “the periods of ‘during an attack’ or ‘hours immediately’ after an attack may not always be when civilians are at greatest risk from submunitions”.Footnote 97 Similarly, the Committee Established to Review the NATO Bombing Campaign against the Federal Republic of Yugoslavia also referred to a standard based on the “long-term effects”: “even when targeting admittedly legitimate military objectives, there is a need to avoid excessive long-term damage to the economic infrastructure and natural environment with a consequential adverse effect on the civilian population”.Footnote 98 An extreme example is the case of a nuclear attack, where it is certainly foreseeable that the attack is likely to result in casualties not only in the days, weeks and months following the attack, but also during the subsequent years and decades.Footnote 99
A third view, according to Rogers, is that the issue of longer- or shorter-term effects probably “does not matter so long as the same timescale is applied to both limbs” of the proportionality test.Footnote 100 This is a controversial approach given that the scope of incidental damage is not qualified in Article 51(5)(b) by any adjectives. Thus, whilst the anticipated military advantage is limited to the “direct and concrete” military advantage – meaning that which is “substantial and relatively close” and not that which is “hardly perceptible” or “which would only appear in the long term” – as explained above, there is no reason based on the text of AP I to likewise limit the scope of incidental damage to “direct and concrete”.
While the very nature of reverberating effects means that they will typically not take place immediately,Footnote 101 identifying a precise temporal scope for foreseeable reverberating effects is challenging. In this regard, it is important to query the added value of identifying the precise temporal scope of the effects that must be taken into account. On the one hand, specific temporal measurements risk being arbitrary. On the other hand, the temporal scope of broader phrases such as “long-term effects of an attack” remains ambiguous. Additionally, there is not necessarily a direct correlation between the foreseeability of reverberating effects and the time at which the effects eventuate. Indeed, the effects of an attack may be foreseeable and take place months or years in the future (e.g. environmental damage), or they may be unforeseeable and take place in the days following an attack (e.g. contamination of water due to an oil spill). Accordingly, it is preferable to focus on the objective foreseeability of the reverberating effects of an attack, regardless of the time at which such effects eventuate, meaning, those reverberating effects that are likely to occur based on the information reasonably available to the commander at the time of the attack.Footnote 102
Material scope of “foreseeability”
Regarding the material scope of the obligation to consider the reverberating effects of an attack, it is clear that it is not possible to establish clear-cut boundaries regarding the types of effects that should be taken into account. That said, it is helpful to identify some effects that may be considered reasonably foreseeable for the purposes of assessing the incidental harm that can be expected from an attack.
As a starting point, the rules on proportionality and precautions in attack both limit the types of harm, including reverberating effects, which are to be taken into account by explicitly referring to the expected incidental “loss of civilian life, injury to civilians and damage to civilian objects”. In interpreting these terms, it is argued that loss of civilian life includes the death of military medical and religious personnel, who are considered civilians for the purposes of the IHL rules on the conduct of hostilities.Footnote 103 Additionally, it is widely held that damage to civilian objects includes loss of functionality of a civilian objectFootnote 104 as well as environmental damage.Footnote 105 Finally, given that the ordinary meaning of “injury” includes both “an instance of being injured” and “the fact of being injured; harm or damage”,Footnote 106 “injury” should be understood broadly to include wounding as well as illness and disease. This view is supported in the Tallinn Manual on the International Law Applicable to Cyber Warfare (Tallinn Manual), which concludes that “serious illness and severe mental suffering that are tantamount to injury” also fall within the scope of incidental harm.Footnote 107
The idea that psychological injury should be taken into account in the proportionality assessment and in the application of the precautionary rules is increasingly accepted.Footnote 108 Moreover, there is no principled reason for restricting injury to physical injury, when its scope is acknowledged to include illness and disease, as there are also mental illnesses that may result from an attack. Lieblich relies on the IHL prohibition against terrorizing civilians and recent research on post-traumatic stress disorder to argue that “incidental mental harm cannot be brushed aside … if IHL is to maintain its integrity as a legal body aiming to minimize civilian harm”.Footnote 109 While it is generally considered that mere inconvenience, stress or anxiety do not enter into the proportionality assessment,Footnote 110 it is submitted that this should not be read as a rejection of the relevance of more severe mental suffering, but rather as a demonstration that the less severe the injury – whether physical or mental – the less likely it is that the incidental civilian damage will be considered excessive compared to the anticipated military advantage.Footnote 111
In addition to loss of civilian life, injury to civilians and damage to civilian objects, it has been argued that the types of harm which are relevant for the rules on proportionality and precautions in attack should be interpreted more broadly to include other humanitarian consequences – for example, displacement or economic hardship caused by contamination and loss of functionality of farming land. This approach has received some support. For example, Norway has previously expressed the view that military commanders should take into account “the humanitarian consequences caused by the attack” and the “more long-term humanitarian problems”.Footnote 112 Likewise, the recent report of the UK Iraq Inquiry (investigating the UK military intervention and presence in Iraq from 2003 to 2009) indicates that
a Government has a responsibility to make every reasonable effort to identify and understand the likely and actual effects of its military actions on civilians. That will include not only direct civilian casualties, but also the indirect costs on civilians arising from worsening social, economic and health conditions.Footnote 113
Adopting an even broader view, Reynolds argues that a “thorough indirect collateral damage assessment must evaluate all foreseeable effects of a military operation on violence, crime, political infrastructure, housing, environment, public health, water and sanitation infrastructure, power infrastructure, poverty, economy, labour and unemployment and education”.Footnote 114
Although many of these effects, particularly displacement, may be a reasonably foreseeable consequence of a particular attack, it is clear that the scope of incidental harm which must be taken into account is limited to loss of civilian life, injury to civilians and damage to civilian objects. As such, even under a broad interpretation of “injury,” incidental harm does not include effects such as poverty, unemployment or economic capacity. For example, the US Law of War Manual takes a clear position that some economic harm is too remote, although “the death of an enemy combatant might cause economic harm in the form of lost jobs; the attacker would not be required to consider such loss in applying the proportionality rule”.Footnote 115 That said, some effects – including, for example, displacement – may still be relevant. Indeed, it may be reasonably foreseeable that displacement will result in increased mortality and deteriorating health of displaced persons, which fall squarely within the types of harm that must be taken into account. In addition, reasonably foreseeable displacement may be relevant in determining the weight to be given to destruction of civilian houses in the proportionality assessment.Footnote 116 For instance, if it is reasonably foreseeable that incidental destruction of civilian houses will result in large-scale displacement, this may change the value given to the houses when assessing whether the expected incidental damage is excessive in relation to the direct and concrete military advantage.Footnote 117
Geographical scope of “foreseeability”
A final dimension to consider is the geographical scope of the reverberating effects of an attack that must be taken into account by planners and decision-makers. In relation to the use of explosive weapons in populated areas, the incidental effects of an attack will be centred on the impact area of the explosion but may also include significant effects beyond the immediate impact zone. In particular, the interdependency of essential services in populated areas means that such services are vulnerable to the “domino effect” whereby a disruption in one service in the environs of the impact area can disrupt another service far away from it. For example, damage to distribution lines may cut off water supply to a larger number of persons than those in the immediate impact zone.Footnote 118 While it is important to recognize that reverberating effects may take place over a wide geographical area, similarly to the temporal scope, it does not seem possible to identify a geographical cut-off point. Rather, it appears more appropriate to focus on which reverberating effects are foreseeable in a particular circumstance. This is reflected in a comment made by Egypt during the Diplomatic Conference of 1974–77, according to which a geographical limitation to the rule on proportionality “introduced a certain ambiguity into the article without necessarily ensuring the protection of civilians, for the loss and the damage had to be considered regardless of the geographical factor so long as the link of causality existed”.Footnote 119
Foreseeable reverberating effects of using explosive weapons in populated areas
Having examined the meaning and scope of the obligation to take into account the foreseeable reverberating effects of an attack, what are the implications for the use of explosive weapons in populated areas? Recent armed conflicts have confirmed that using explosive weapons in populated areas has a significant and devastating impact on civilians, including “destruction and damage of civilian residences and critical civilian infrastructure, with consequent disruption to essential services, such as health care and water distribution, and displacement of the civilian population”.Footnote 120 In particular, the use of explosive weapons in populated areas affects the ability of health-care facilities and services to operate and cope with the influx of wounded people and the injuries they present, and to provide adequate care.Footnote 121 It also has a long-term impact on mental well-being.Footnote 122 There is growing public awareness of the indirect effects caused by the use of explosive weapons in populated areas.
When explosive weapons are employed in populated areas, the reasonably foreseeable reverberating effects will usually arise from incidental damage to or destruction of civilian objects. Of course, the expected damage/destruction of such objects is relevant as such; but in many cases, such damage/destruction will also entail foreseeable reverberating effects for the civilian population. For example, an attack in a populated area using weapons with large blast and fragmentation effects may be expected to cause incidental damage to components of the electricity network in the area of the attack (e.g. electricity transmission lines or transformers).Footnote 123 While the precise effects of the attack would depend on the extent of the damage and the number of people affected, it is reasonably foreseeable that hospitals will be affected (particularly if backup generators are not available), which may lead to loss of civilian life or injury to civilians.Footnote 124 Likewise, damage to components of an electricity network may also affect water purification, storage and distribution systems. Damage to such systems can have significant and foreseeable reverberating effects on the health and well-being of the affected civilian population. For example, civilians may lose access to potable water and be forced to access unregulated and alternative water sources, leading to an increased risk of waterborne diseases. Acknowledging this possibility, US Joint Publication 3–60 (Joint Targeting) specifically requires that
[i]f the attack is directed against dual-use objects that might be legitimate military targets but also serve a legitimate civilian need (e.g., electrical power or telecommunications), then this factor must be carefully balanced against the military benefits when making a proportionality determination.Footnote 125
Moreover, essential infrastructure which if damaged or destroyed would have significant reverberating effects for civilians is in most cases located above ground and visible to a trained eye.Footnote 126 This means that commanders should normally be aware of civilian infrastructure located in the vicinity of a military objective and should take into account the foreseeable reverberating effects of damaging such infrastructure. Additionally, in many contexts, commanders would have access to information on underground supply networks which must also be taken into account for the purposes of assessing the incidental civilian damage that is expected to result from an attack.
Regarding existing military policy and practice, there is limited information in the public domain on whether (and if so, how) armed forces take into account the reverberating impacts of explosive weapons that have wide area effects. The United Kingdom's Joint Service Manual of the Law of Armed Conflict (UK Joint Service Manual) states that “when used against targets in an urban or populated environment, artillery may be expected to cause a lot of incidental damage which would need to be considered in relation to the anticipated military advantage”.Footnote 127 Moreover, the US Counterinsurgency Manual provides that employing tactics and weapons appropriate to the situation “[i]n some cases … means avoiding the use of area munitions to minimize the potential harm inflicted on non-combatants located nearby”.Footnote 128 While these policies do not relate specifically to the objectively foreseeable reverberating effects of an attack, they provide important examples of policy guidance based on past observations, which effectively put commanders on notice that the use of artillery in a populated area can be expected to cause significant incidental harm.
Further, in requiring that commanders consider the foreseeable effects of an attack for the purpose of the rule on proportionality, the UK Joint Service Manual includes a second noteworthy example. In the context of precision bombing, the Manual notes that if
an attack of a military fuel storage depot is planned but there is an expectation that the burning fuel will flow into a civilian residential area and cause injury to the civilian population which would be excessive in relation to the military advantage anticipated, that bombardment would be disproportionate and unlawful, owing to the excessive collateral damage.Footnote 129
Another example is the African Union Mission in Somalia (AMISOM) Indirect Fire Policy, issued in 2011 to incorporate past practices and lessons learned in Somalia. The policy restricted the use of mortars and required a stricter chain of command for authorization of the use of mortar and artillery fire. It also created no-fire zones where civilians were known to be present.Footnote 130
Foreseeable reverberating effects and the obligation to take all feasible precautions in attack
As is noted in the ICRC Commentary to Article 57 of AP I, the rule of precautions in attack is “of greatest importance in urban areas because such areas are most densely populated”.Footnote 131 With the previous section having set out the conceptual framework and scope of the obligation to take into account the expected incidental damage resulting from an attack, including the reasonably foreseeable reverberating effects, the following section focuses on practical steps to be taken by commanders in order to exercise the objective degree of diligence required in fulfilling their obligations. In particular, this section will examine the feasible precautionary measures required to ensure that the reasonably foreseeable reverberating effects of an attack are adequately assessed. Feasibility is a relative standard which requires that attackers take precautions that “are practicable or practically possible taking into account all circumstances ruling at the time, including humanitarian and military considerations”.Footnote 132 While not imposing an absolute obligation of conduct, compliance with the rule of precautions in attack is also informed by the standard of the reasonable military commander. This means that attackers must take those measures “that a reasonable attacker would take in the same or similar circumstances” based on information “reasonably available [to the attacker] at the relevant time and place”.Footnote 133
The obligation to refrain from deciding to launch an attack that may be expected to violate the rule of proportionality
The obligation to refrain from deciding to launch a disproportionate attack requires that commanders “do everything feasible to assess whether the attack may be expected” to be disproportionate.Footnote 134 This includes doing everything feasible to assess the reasonably foreseeable reverberating effects of the attack.
While the concept of feasible precautions is fairly well established, it is not entirely clear how this obligation translates in practice. Are military commanders obliged to obtain information regarding the location of civilian objects that are critical to the provision of essential services? Is there an obligation to obtain technical expertise or guidance regarding the effects on the civilian population if particular civilian objects are damaged or destroyed? It is clear that the extent to which certain reverberating effects will be foreseeable in part depends on the level of expertise that goes into the assessment of incidental civilian damage. Moreover, should a distinction be drawn between what is considered feasible in a pre-planned attack as compared to an unplanned attack?
Quality and quantity of information
Regarding the quality and quantity of information that is required to assess the reasonably foreseeable reverberating effects of an attack, a number of States have explicitly declared that military commanders must make their decisions on the basis of the information that is available to them at the time of the attack,Footnote 135 whilst others have referred to information that is “reasonably available”.Footnote 136 In reference to a standard of reasonableness, Rogers takes the view that the test “will depend to some extent on the amount of information readily available, the staff at hand to deal with it and whether that information raises questions that require further research of other sources of information”.Footnote 137 In addition, a number of military manuals require commanders to obtain “the best possible intelligence”Footnote 138 regarding aspects relevant to the assessment of incidental damage. For example, Australia's Law of Armed Conflict Manual requires the best possible intelligence concerning “concentrations of civilians; civilians who may be in the vicinity of military objectives; [and] the nature of built-up areas such as towns, communities, [and] shelters”.Footnote 139 Although not explicitly specified, such an approach may require not only information regarding the location of essential infrastructure but also an understanding of the interconnectedness of essential services.
Practically speaking, it may be possible in some cases for militaries to obtain information relating to the location of essential civilian infrastructure and supply networks, including primary infrastructure (e.g. water distribution networks, water treatment plants, electricity generating plants) as well as secondary and tertiary infrastructure (e.g. transmission lines or sub-transformers). Availability of this kind of information will vary depending on the context: in some situations it may be publicly available (including online), while in other cases, particularly in the early stages of an operation, such information might not be easily accessible. In this regard, it should be noted that essential civilian infrastructure will typically be located at ground or above-ground level and will thus be visible to an expert eye (e.g. civil engineer).Footnote 140
Assessments of the foreseeable reverberating effects of an attack are likely to require technical expertise, including from engineers and/or public health experts. For example, in relation to computer network attacks, the Tallinn Manual recommends that where feasible, technical experts should be available to assist mission planners in determining whether appropriate precautionary measures have been taken.Footnote 141 In the view of Droege, in the absence of such expertise, it may even be necessary for the attacker to refrain from the computer network attack.Footnote 142 In the context of urban warfare, Boothby also implies that an assessment of the expected incidental damage should involve technical expertise: when attacks in urban areas
may be expected to damage utilities on which the civilian population relies, an assessment should be made of how long it is likely that the relevant services will remain out of action and what damage, injury, and death civilians are likely to suffer during that period as a result.Footnote 143
As noted by one expert, “a war-fighter does not normally have the necessary training to assess the public health risks of an attack”.Footnote 144 Thus, it will normally be necessary to incorporate specialists into targeting assessments.
In practice, some militaries already incorporate engineering expertise into targeting processes, in order to provide expertise on the physical impact of certain weapons on targeted buildings.Footnote 145 In addition, the US Army Field Manual on Intelligence Support to Urban Operations refers to the role for engineers in assessing “potential collateral damage by analysing risks of damage caused by the release of dangerous forces, power grid and water source stability, and the viability of sewage networks”.Footnote 146
More generally, it appears that some States have policy guidance and processes which require detailed analysis of essential infrastructure, which could feasibly be used for the purpose of assessing the expected incidental harm, including the foreseeable reverberating effects, of an attack. For example, the US manual Joint Urban Operations (US Joint Urban Operations Manual) emphasizes the importance of “critical infrastructure analysis” during the planning phase of an operation:
Critical infrastructure analysis is a combination of intelligence preparation, the targeting process, and staff planning. Its purpose is to examine closely the nature of the infrastructure systems and their components …. The initial steps in the critical infrastructure analysis will identify certain infrastructure to be preserved, protected, or to which damage should be minimized …. The targeting process should recognize the facilities or structures to be protected and give careful consideration to potential collateral damage resulting from attacks on nearby targets.Footnote 147
Although the US Joint Urban Operations Manual does not define “critical infrastructure”, it notes that systems and facilities may be selected for analysis for several reasons, including “[i]nfrastructure whose destruction would cause hardship for civilians”.Footnote 148 Other States such as Israel and Norway also give specific attention to the importance of minimizing damage to civilian infrastructure.Footnote 149 If the impact of warfare on essential infrastructure is already the subject of intensive intelligence gathering and analysis, the gathering of such intelligence is at least in some circumstances considered feasible, and should in those circumstances also inform the assessment of the expected incidental damage, including the foreseeable reverberating effects.
It is not entirely clear how militaries assess the foreseeable reverberating effects of an attack. However, it appears that this may occur in part through the use of advanced CDM processes. For example, the US CDM requires both an environmental damage assessment and an assessment of the chemical, biological and radiological (CBR) Plume Hazard for each attack,Footnote 150 noting that “special consideration must be given to the secondary and tertiary effects of engaging these types of targets”.Footnote 151 Likewise, the US CDM requires special consideration of dual-use facilities, meaning “those valid military targets characterized as serving both a military and civilian (i.e. non-combatant) purpose/function”.Footnote 152 Aside from attacks on dual-use facilities, it remains unclear if and how the US CDM includes an assessment of the foreseeable reverberating effects of attacks on other military objectives. Although it has not been possible to access CDM used by other militaries, it should be noted that the 2009 Australian military manual makes it clear that the collateral effects of an attack – including second- and third-order consequences which are unintended – “should be a major, deliberate consideration in planning, executing, and assessing military actions on any scale”.Footnote 153
Pre-planned attacks vs. unplanned attacks
An issue related to the quantity and quality of information that a commander can feasibly be expected to take into account when analyzing the expected incidental damage of an attack is the relevance of the operational context. In a pre-planned attack, it might be both feasible and reasonable for commanders to consult experts prior to the attack, such as their medical or engineering branch, in order to estimate the incidental damage of the attack. Such information will likely render certain reverberating effects foreseeable that would not be foreseeable in unplanned operations. In a “troops-in-contact” (TIC) scenario, where friendly forces are under effective fire,Footnote 154 a reasonable commander would not be expected to proactively engage in extensive intelligence gathering before responding to incoming rounds, although pre-existing knowledge would still need to be taken into account. In unplanned operations other than TIC scenarios, where friendly forces are not in immediate danger but where “dynamic targeting” is employed to pursue a militarily important target of opportunity,Footnote 155 the military considerations weighing in favour of an immediate engagement are likely tempered to a greater extent than in TIC scenarios by the precautionary obligation to proactively gather information prior to an attack in order to inform the estimation of incidental damage.
While the condition of feasibility introduces some malleability into the rule of precautions in attacks, thereby accommodating different operational realities,Footnote 156 it does not altogether suspend the IHL obligation to take precautions in attack. Feasibility explicitly refers to military and humanitarian considerations. Thus, even in TIC situations, the attacker must gather a reasonable amount of information to inform his or her decision and must take into account those reverberating effects that are reasonably foreseeable,Footnote 157 including based on prior knowledge of the operational environment, training and past experiences.Footnote 158 For instance, the on-scene commander should be trained on the general effects of the weapon system being used and should be able to reference training and intelligence relating to demographics, typical civilian patterns of life and types of structures commonly occupied by civilians.Footnote 159 The rule of precautions in attack is violated where feasibly available information is not obtained or is ignored, irrespective of the operational context.Footnote 160
The obligation to take all feasible precautions in the choice of means and methods of attack
Commanders are obliged to take all feasible precautions in the choice of means and methods of attack with a view to avoiding or minimizing the expected incidental harm,Footnote 161 including the reasonably foreseeable reverberating effects of an attack. Compliance with this obligation will of course depend on the particular context, but will require assessment of the foreseeable effects of the available weapon systems, in view of their technical characteristics and the expected circumstances of their use. This should also include consideration of the way in which the technical features of each weapon can be manipulated, so as to minimize the foreseeable direct and indirect effects on civilians, including the type and size of the warhead, the type of fuse, the delivery system, the distance from which the weapon is launched, as well as the angle and timing of the attack.Footnote 162
In this respect, it should be noted that technological development has rendered measures that were militarily unfeasible in the past, feasible today. Schmitt has suggested that increasing attention on reverberating effects is in part due to technological developments in targeting capabilities: “Of course, reverberating effects were theoretically always calculated when assessing proportionality. However, it is only now that the means exist to limit dramatically direct collateral damage and incidental injury that we are being sensitized to reverberation.”Footnote 163 In other words, reverberating effects are now more relevant because new technology – including precision-guided missiles – enables attackers to be more precise in limiting the reverberating effects of an attack. A similar line of argument can also be applied to advanced CDMs, which use physics-based computer modelling to estimate and mitigate incidental civilian harm.Footnote 164 Indeed, the existence and use of more sophisticated means of measuring incidental damage has increased the capacity of commanders to calculate the reverberating effects of an attack, thereby making them more relevant.Footnote 165
This is an interesting approach to the issue, and it is indeed true that greater accuracy in weapons systems or greater capacity to calculate incidental damage may increase the possibility to minimize the reverberating effects of an attack.Footnote 166 However, it must be emphasized that the obligation to incorporate the foreseeable reverberating effects of an attack into targeting assessments is not dependent on the level of technology of a party to an armed conflict. Even militaries that are not using precision weapons and sophisticated means of measuring incidental damage can assess the foreseeable reverberating effects of an attack, particularly when using explosive weapons with a wide impact area in populated areas. This is especially true in the case of reverberating effects resulting from incidental damage to civilian objects. As most essential infrastructure is located at ground or above-ground level, it is visible to a trained eye and must be taken into account when assessing the foreseeable reverberating effects of an attack, regardless of technological developments in targeting capabilities. Additionally, an assessment of the foreseeable reverberating effects of an attack should be informed by lessons learned from previous conflicts and what is known in the public domain about the environment surrounding the target, and about the effects of specific weapons, including explosive weapons with a wide impact area. Thus, while technology may allow for a more demanding threshold regarding what is feasible or foreseeable, the obligation to take into account the reverberating effects of an attack is not dependent on having sophisticated technology such as precision-guided munitions or a sophisticated CDM process.
One question arising from the interpretation of this rule is whether it requires the employment of precision-guided munitions. This question is particularly relevant to the use of explosive weapons that are prone to wide area effects in populated areas. As the law currently stands, the answer to this question is somewhat nuanced. Despite arguments to the contrary,Footnote 167 there is no existing legal obligation to acquire the most precise weapons available on the market, or, once obtained, to use precision-guided munitions in all situations.Footnote 168 However, where such weapons are available, and their use is feasible, and they would allow the attacking party to avoid or minimize the expected incidental harm (including the reasonably foreseeable reverberating effects), they should be used.Footnote 169 Accordingly, Dinstein notes that if an attack is planned on “a small military objective located in the middle of a densely populated civilian area, the only modus operandi minimizing the expected collateral damage to civilians may be the employment of [precision-guided munitions]”.Footnote 170 In a similar vein, Schmitt suggests that the obligation to minimize incidental damage may be complied with through the use of low-collateral weapons such as carbon filament bombs, which “can be used to interrupt electricity with far less collateral damage than regular bombs”.Footnote 171 That being said, it must be emphasized that while precision-guided munitions or other sophisticated weapons may increase the capacity of the attacker to minimize the expected incidental harm of an attack, the use of such technology does not ensure compliance with the rule on proportionality in attack. Large precision-guided explosive munitions are also prone to indiscriminate effects due to their wide blast and fragmentation range. Regardless of the type of weapon used, if an attack is expected to be disproportionate, the commander must refrain from launching, or must suspend or cancel, the attack.
Regarding the use of less precise explosive weapons in populated areas, the obligation to minimize incidental casualties or damage to civilian objects may also trigger precautionary measures such as the establishment of no-fire zones or restrictions on the types of situations in which particular weapons can be used. For example, the 2011 US Army manual Combined Arms Operations in Urban Terrain (US Combined Arms Manual) notes that in regard to the use of field artillery in operations in urban terrain, “restrictive fire support coordination measures, such as a restrictive fire area or no-fire area may be imposed to protect civilians and critical installations”.Footnote 172 Similarly, the 2013 US Joint Urban Operations Manual indicates several precautionary measures that can be taken in relation to the use of weapons fire in urban environments, including “restricting munitions used in the attacks” and “aborting attacks unless accuracy can be guaranteed”.Footnote 173 Another prominent example is the restrictions on high-explosive (HE) artillery that were put in place by the Israeli Defence Force (IDF) during the armed conflict in Gaza in 2014.Footnote 174 Although Israel was clear to underline that these directives were going beyond the requirements of IHL, they put in place a general prohibition on the use of HE artillery shells in populated areas and required the observance of specified “safety margins”.Footnote 175 Accordingly, HE artillery could only be used in populated areas on an exceptional basis where there was “an imperative military necessity for artillery fire support”.Footnote 176 These examples are illustrative of a certain acknowledgement by some armed forces of the fact that certain explosive weapon systems may be expected to result in substantial incidental damage when used in populated areas.
Aside from the choice of weapon, a particularly important aspect of complying with this obligation is the ability to manipulate the technical features of the chosen weapon system, in order to minimize incidental civilian harm, including foreseeable reverberating effects. For example, choices regarding the warhead, type of munitionFootnote 177 and fusing can be made in order to minimize the effects of the attack on civilians and civilian objects located within the impact area.Footnote 178 In this regard, the US Combined Arms Manual places specific restrictions on the use of fuses on mortars in an urban environment: “When using HE ammunition in urban fighting, only point-detonating fuzes should be used. The use of proximity fuzes normally should be avoided because the nature of urban areas causes proximity fuzes to function prematurely.”Footnote 179 Policy directives regarding fusing were also implemented by the IDF during the 2014 conflict in Gaza whereby “in certain cases, the IDF employed delay fuses for bombs to detonate deep inside targets, to limit damage to adjacent structures”.Footnote 180 Considerations such as warhead type and fusing are also incorporated into the CDM used by several militaries.Footnote 181
In addition, parties to an armed conflict should take feasible precautions in relation to the angle of attack.Footnote 182 This is extremely important, particularly in densely populated areas, as the angle of an attack will influence the extent and direction of secondary fragmentation resulting from the attack – i.e., gravel, cement, wood, rocks, glass and metal which may be projected out by the blast wave.Footnote 183 By carefully managing the angle of attack, fragmentation effects can be shaped and mitigated so as to reduce the risk of civilian casualties and damage to civilian objects.Footnote 184 For example, by changing the angle of attack against a particular military objective in a populated area, it may be possible to ensure that secondary fragmentation is projected upwards or in the direction of an uninhabited block, rather than in the direction of a medical clinic. As the angle of attack is usually incorporated into CDM or other means of preparing an attack, in most cases it will be feasible to take such precautions.Footnote 185
Finally, the obligation to take all feasible precautions in the choice of means and methods of attack can also “impose restrictions on the location of an attack, by requiring, where circumstances permit, that parties avoid attacking a densely populated area if the attack is likely to cause heavy civilian losses”.Footnote 186 Indeed, in some cases, where there are no alternative means or methods of attack which would minimize incidental civilian damage, the only feasible option is to refrain from launching an attack that would be disproportionate or indiscriminate. Although framed as a way of reducing operational- and tactical-level implications (rather than as a legal obligation), this precautionary measure is reflected in the US Joint Urban Operations Manual in relation to the use of weapons fire in urban environments. Acknowledging that the presence of civilians can severely inhibit the use of weapons fire, the Manual refers to several measures that can be taken, including “prohibiting attacks on targets located in heavily populated areas”.Footnote 187
Conclusion
Although the rules on proportionality and precautions in attack require that reverberating effects are taken into consideration for all attacks, this obligation is particularly relevant in the context of attacks involving the use of explosive weapons that have wide area effects in a populated area. Indeed, recent conflicts have shown that when explosive weapons with a large destructive radius, an inaccurate delivery system or the capacity to deliver multiple munitions over a wide area are used in populated areas, there is a high likelihood that civilians will be killed and injured, and essential civilian infrastructure will be damaged or destroyed, with consequent disruption in essential services and subsequent effects on the lives and well-being of the civilian population.
In fleshing out its contextual scope and framework, this article has argued that the obligation to take into account the reasonably foreseeable reverberating effects of an attack derives from the requirement to estimate the “expected” incidental damage of an attack when applying the rules of proportionality and precautions in attack. This obligation imposes an objective standard of care, based on the standard of the “reasonable commander”. This implies that commanders must take into account those reverberating effects that are reasonably foreseeable in the circumstances ruling at the time, in light of the reasonably available information. Moreover, the objective standard of “reasonable foreseeability” means that commanders are put on notice regarding reverberating effects that may be considered reasonably and objectively foreseeable based on past practice and empirical research, lessons learned and publicly available information, including information about the reverberating effects of using explosive weapons in populated areas.
The obligation to take into account the reasonably foreseeable reverberating effects of an attack is reinforced by the precautionary obligation to refrain from launching a disproportionate attack, which imposes a duty to proactively gather information that will inform the assessment of the expected incidental damage of the attack. This includes, where feasible, obtaining information regarding the location and nature of essential infrastructure and ensuring that relevant technical experts are involved in assessing the expected incidental harm of an attack. While the operational context might impact the extent to which a commander is expected to proactively gather information to inform the estimation of incidental damage, a commander may never ignore reasonably available information, including such information that renders the reverberating effects of an attack reasonably foreseeable.
Additionally, all feasible precautions must be taken in the choice of means and methods of attack, by assessing the foreseeable effects of particular weapons, including reverberating effects, on the basis of their technical characteristics and the expected circumstances of their use. Feasible precautions include manipulating the technical features of explosive weapons such as the type of fuse and the type/size of the warhead, as well as considering the timing, angle and location of the attack. Yet even such precautions may not be sufficient to obviate the wide area effects of certain explosive weapons. In such cases, the only option may be to refrain from using the weapon, if its use is likely to lead to a violation of the prohibition on indiscriminate and disproportionate attacks.
As is the case currently for some militaries, policy guidance should be put in place to identify which kinds of precautions in attack can and should be implemented, in order to assess and minimize the reverberating effects of an attack using explosive weapons in populated areas, building on good practices already applied by a number of militaries. Likewise, when it is reasonably foreseeable that using a particular explosive weapon in a populated area will result in excessive incidental civilian harm, military manuals and policy should set out clear restrictions on the use of those weapons in populated areas. Although it is not possible to foresee and limit all of the possible effects of an attack, a lot more can be done to better understand the reverberating effects of an attack using explosive weapons in populated areas and to develop policy guidance setting out if and how such weapons should be used.
