Indiscriminate Attacks, Proportionality and the Meaning of “Incidental” Civilian Harm

Editors’ note: This post is based on the author’s article, “Indiscriminate Attacks and the Proportionality Rule: What is Incidental Civilian Harm?” in the Journal of Conflict and Security Law.

What does it mean for civilian harm to be “incidental” within the meaning of the proportionality rule of the law of armed conflict (LOAC)? The answer carries profound consequences for how we distinguish lawful military operations from indiscriminate attacks.

Surprisingly, scholars have so far paid little attention to this question. A recent article and accompanying blog post have made a major contribution to the question, however. In a nutshell, the article and post argue in favour of what we might call the “Lesser Effects Thesis.” This suggests that civilian harm qualifies as “incidental” for the proportionality rule only if it is a mere side-consequence of an attack, rather than its main or prevalent effect, understood in quantitative terms. Taken to its logical conclusion, the Lesser Effects Thesis holds that if an attack against a military objective is expected to harm as many or more civilians or civilian objects as the number of lawful targets, then this civilian harm is not truly incidental. Instead, the attack would be outright indiscriminate and fall outside of the proportionality rule.

As I argue in more detail in this article, the Lesser Effects Thesis is open to a range of objections. Civilian harm is incidental when it constitutes the fortuitous and undesired consequence of an attack directed against a military objective. The fact that the attack is expected to affect a similar or larger number of civilians or civilian objects than military objectives does not prevent the civilian harm from being incidental. The purpose of this post is to briefly explain why.

The Proportionality Rule

The proportionality rule is a prime example of the pragmatism that sustains LOAC. If the law prohibited incidental civilian harm completely, belligerents would find it impossible to prevail over their adversaries without violating such a comprehensive prohibition. Conversely, if the law imposed no limits at all, the principle of distinction could be hollowed out by attacks causing overwhelming levels of civilian harm as a mere by-product of targeting lawful military objectives.

The proportionality rule balances these considerations by recognizing that some degree of incidental civilian harm is unavoidable and hence must be permissible. Yet, the proportionality rule also seeks to keep the risk to civilians and civilian objects within tolerable bounds by setting an upper ceiling that such harm may not cross.

The basic idea is straightforward enough. However, in the absence of an express definition of the term, it is not immediately clear what qualifies as “incidental” civilian harm for these purposes. Comparing proportionality with other targeting rules offers some initial clues.

Proportionality and Indiscriminate Attacks

It is common ground that proportionality comes into play only if civilians or civilian objects are not the deliberate targets of an attack. An attack directed against civilian persons (Additional Protocol (AP) I, art. 51(2)) or civilian objects (AP I, art. 52(1)) violates the principle of distinction outright, and the analysis never even reaches the question of proportionality.

Attacks not directed at a specific military objective are also prohibited (AP I, art. 51(4)(a)). Although not deliberately targeting civilians or civilian objects, such attacks are indiscriminate because they make no attempt whatsoever to comply with the principle of distinction. Blind fire in the general direction of the enemy provides one example. Such attacks are forbidden in absolute terms and do not engage proportionality.

Methods or means of combat that cannot be directed at a specific military objective are indiscriminate too (AP I, art. 51(4)(b)). This rule prevents a party from claiming that it is directing its attacks against lawful objectives when, in fact, it is using methods or means that are incapable of being so directed. Once again, the analysis does not reach the question of proportionality, as the attacking party is, from the outset, not targeting a specific military objective.

Finally, attacks which employ a method or means of combat the effects of which cannot be limited as required by AP I are indiscriminate (AP I, art. 51(4)(c)). The rule applies to attacks directed against lawful targets, which produce effects that cannot be sufficiently limited. This is an important point. These types of attacks are indiscriminate not because they fail to distinguish at all, but because they are insufficiently discriminating. Attacks causing excessive levels of incidental civilian harm fall into this basket.

What Can We Take from This?

Proportionality comes into play only in cases where an attack is directed against a military objective and is not directed against civilians or civilian objects. This does not sound like much. However, it highlights that the AP I targeting rules are concerned with how attacks are directed that is, the decision-making process for determining who or what the target of the attack should be (Ntaganda, para. 744), rather than with their actual outcomes. As the text of AP I emphasizes, indiscriminate attacks are prohibited because they are not properly directed, cannot be properly directed, or cannot be properly limited and, as such, “are of a nature to strike military objectives and civilians or civilian objects without distinction” (AP I, art. 51(4), emphasis added).

Accordingly, a grenade intentionally thrown at a civilian or a missile blindly fired into a suburban neighbourhood constitutes an indiscriminate attack even if the grenade or missile causes no harm to civilians or civilian objects (Katanga, para. 37). In these two examples, the attacks are not properly directed and therefore are of a nature to strike without distinction, whether or not they actually strike civilians or civilian objects.

Conversely, violence directed against what the attacker believed to be a lawful military objective does not, without more, become an indiscriminate attack just because the target subsequently turns out to be a civilian or civilian object, even though the attacker engaged and harmed it deliberately (Ermittlungsverfahren gegen Oberst Klein, p. 51; BVerfG 2 BvR 987/11, para. 29). Similarly, without more, the mere fact that civilians or civilian objects suffer harm directly and in the same manner as the military objective targeted does not necessarily mean that the attack was directed against those civilians and civilian objects, rather than a military objective (Katanga, para. 875). In the latter case, the proportionality rule may therefore be engaged.

Incidental: Direct or Indirect Effects?

The Lesser Effects Thesis takes a different view and suggests that only indirect harm qualifies as incidental. Undoubtedly, civilian harm is incidental when it is the indirect, secondary effect of an attack. For instance, an airstrike on an enemy ammunition depot may set off secondary explosions, which in turn may damage nearby residential buildings. Such secondary damage is perhaps the paradigmatic example of incidental civilian harm, but it is not the only type.

First, it is widely accepted that harm suffered by civilians or civilian objects present inside a military objective as a result of an attack on the latter is incidental in nature (see, e.g., International Committee of the Red Cross (ICRC) Draft Additional Protocols to the Geneva Conventions, p. 59; Danish Ministry of Defence Military Manual on International Law Relevant to Danish Armed Forces in International Operations, p. 317). This is true even though the harmful effects on civilians or civilian objects may be immediate, direct, and indistinguishable from the effects on the intended target.

Second, an attack directed against a military objective may affect the target and nearby civilians or civilian objects simultaneously and primarily, rather than secondarily. For example, a mortar shell may explode halfway between a military objective on one side and a civilian object on the other. If such harm does not qualify as incidental in nature for the same reasons as the previous type, the use of any weapon the effects of which the attacker cannot wholly contain within the military objective they targeted would constitute an indiscriminate attack. That does not reflect practice.

Third, some weapons, such as artillery or landmines, may harm civilians or civilian objects directly without also having a simultaneous effect on the intended military objective. This has not prevented such civilian harm from being considered incidental in nature (e.g., Gotovina, para. 1910; Protocol on Prohibitions or Restrictions on the Use of Mines, Booby-Traps and Other Devices, art. 3(8)(c)).

Incidental civilian harm may therefore be indirect and secondary, direct and simultaneous, or direct and non-simultaneous with the desired effect on the lawful target. One difficulty with this is that an attack may be directed against a military objective and also deliberately target civilians or civilian objects at the same time. How are we to distinguish cases where civilians or civilian objects suffer direct harm as an incidental consequence of an attack directed solely against a military objective from cases where the attack deliberately targets them and the military objective in parallel?

Confronted with this question, the Trial Chamber of the International Criminal Court held that an intention to make civilians the object of attack that is directed against lawful targets could be inferred from various factors, including “the means and methods used during the attack, the number and status of the victims, the discriminatory nature of the attack or, as the case may be, the nature of the act constituting the attack” (Katanga, para. 807). This suggests that taking all feasible precautions to avoid or minimize civilian harm implies that the attacker targeted the military objective and that any civilian harm was incidental. A party cannot deliberately target civilians or civilian objects and do everything feasible to avoid harming them at the same time.

Incidental: A Lesser Effect?

The core argument of the Lesser Effects Thesis is that civilian harm qualifies as “incidental” only if it is expected to affect a similar or lower number of civilians or civilian objects than military objectives. The Thesis relies on the prohibition of target area bombardment found in Article 51(5)(a) of AP I, which prohibits “an attack by bombardment by any methods or means which treats as a single military objective a number of clearly separated and distinct military objectives located in a city, town, village or other area containing a similar concentration of civilians or civilian objects.” It suggests that this rule “confirms that even when several lawful targets are the directly intended objective of the attack, it remains absolutely (not relatively!) prohibited to strike them via means or methods that involve the shelling of a similar concentration of protected objects or persons interspersed among the lawful targets (even if several).”

This approach misreads the rule. What the target area bombardment rule prohibits is treating a number of clearly separated and distinct military objectives as a single, overall target. It does not prevent their bombardment individually; indeed, the whole point of the rule is that an attack should be directed against them individually. Moreover, the rule applies when the military objectives are located inside a city, town, village, or any other area that contains a concentration of civilians or civilian objects similar to that found in a city, town, or village. The numerical comparison is between cities, towns, villages, and other areas, not between the number of military objectives and the number of civilians or civilian objects (Official Records, Vol. XV, p. 455; ICRC, AP I Commentary, para. 1973). Accordingly, the rule does not say anything at all about what number of civilians or civilian objects may or may not be affected by attacks directed individually against distinct military objectives.

Applying the rules of treaty interpretation more systematically suggests that civilian harm is “incidental” when it constitutes the fortuitous and undesired consequence of an attack directed against a military objective, with no requirement that the attack must affect only a similar or lower number of civilians or civilian objects. The conceptual counterpart of incidental civilian harm is the deliberate and desired effect the attack is meant to have on the military objective, not the number of military objectives targeted. The history of the AP I negotiation confirms these points, as does the widespread and consistent practice that treats incidental civilian harm as synonymous with “collateral damage,” a phrase that does not imply any relationship of proportion whereby an attack must affect only a similar or lower number of civilians or civilian objects than military objectives.

Putting the rules of interpretation to one side, the Lesser Effects Thesis seems divorced from operational reality. Taken to its logical conclusion, the Lesser Effects Thesis suggests that the proportionality rule would not be applicable where an attack directed against a single military objective is expected to harm a single civilian or civilian object, because the impact on the military objective would not be the main effect of the attack and the impact on the civilian or civilian object its mere side-consequence in quantitative terms. Accordingly, proportionality would not apply to an attack on an enemy armoured vehicle with a rocket-propelled grenade if the explosion is expected to shatter some windows or down a power line. Instead, this would amount to an outrightly indiscriminate attack. This is absurd.

Unsurprisingly, this is not the approach adopted in practice. A case in point is the Collateral Damage Estimation Methodology, used across NATO, the European Union, and by several other States to assist in assessing and mitigating the incidental civilian harm expected from an attack. The Methodology not only reflects how a large number of States understand their legal obligations but also represents their practice in combat operations. It proceeds on the basis that civilian harm is incidental even when the attack affects the same or a substantially higher number of civilians or civilian objects compared to the number of military objectives targeted.

Conclusion

The Lesser Effects Thesis represents a radical re-reading of the proportionality rule that would restrict its application to a narrow set of circumstances and significantly expand the scope of the prohibition of indiscriminate attacks. This is not to suggest that such a radical re-reading of proportionality is an illegitimate endeavour. There is nothing untoward in interrogating the compromises that underpin the existing rules. Nonetheless, prioritizing the “unapologetic protection of civilians” over maintaining the law’s traditional balance between military necessity and humanity (Daniele, p. 28) invites two observations.

First, the Thesis develops arguments in opposition to what it variously calls military-friendly re-translations, misinterpretations, expansive readings, circumventions, conceptual distortions, aporetic constructions, and contra legem inversions of what it believes the law really is. A closer look at the Lesser Effects Thesis suggests it does not reflect the law as it stands, it is contradicted by State practice, and is operationally unsound. The shoe seems to be on the other foot.

More importantly, the way to reinforce the proportionality rule is not by advancing interpretations that seek to increase its constraining effect to a point where it would render the conduct of many military operations all but impossible. The idea that incidentally requires civilian harm to be the lesser effect of an attack is so divorced from operational reality that it has no hope of securing compliance. A better way to safeguard the protective scope of the law is to encourage greater transparency in the conduct of proportionality assessments, to test those assessments against the benchmark of international practice, and to insist on full compliance with precautionary obligations.

With regard to the latter, some might even persuasively argue that the AP I prohibition on attacks which employ a method or means of combat the effects of which cannot be limited (art. 51(4)(c)) includes attacks that fail to choose means or methods of combat more suitable to avoiding or minimizing incidental civilian harm where feasible, as required by Article 57(2)(a)(ii) of AP I. Accordingly, where a party may feasibly choose means or methods of combat that are more likely to avoid or minimize the incidental civilian harm expected from the attack, a failure to do so may render the attack indiscriminate under Article 51(4)(c) of AP I.

This approach would seem to address many of the concerns raised by the Lesser Effects Thesis and by others regarding overly generous invocations of proportionality without, however, re-interpreting the rule in a way that imposes utterly unrealistic expectations.

***

Dr Aurel Sari is a Professor of Public International Law at the University of Exeter and a Fellow of Supreme Headquarters Allied Powers Europe.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.

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