Professor Marco Sassòli
Honorary professor of international law at the University of Geneva, Switzerland
In the context of contemporary armed conflicts and the growing importance of upholding international humanitarian law (IHL), a thorough examination of the rules governing targeting—particularly in light of the principles of distinction, proportionality, and precautionary obligations—has become increasingly essential. The present note provides a systematic overview of the most significant IHL principles and rules on targeting, prepared by Marco Sassòli, Honorary Professor of International Law at the University of Geneva and one of the leading experts in humanitarian law.
In this paper, Sassòli, drawing on the foundational instruments of humanitarian law, including the Additional Protocols to the Geneva Conventions and customary international practice, analyzes the notion of legitimate targets, the scope and limits of direct participation of civilians in hostilities, the concept of dual-use objects, the inherent difficulties of assessing proportionality in attacks, and the special protections afforded to cultural property and the natural environment.
Fundamental principles
Only legitimate targets may be directly targeted. Even then, certain means and methods of warfare may not be used, the expected incidental effects of an attack on the civilian population may not be excessive in relation to the military advantage anticipated, and both the attacker as well as the defender must take measures to avoid and, in any event, minimize such incidental effects.
According to the fundamental principle of distinction codified in Article 48 of Protocol Additional I to the Geneva Conventions (Protocol I), which uncontroversially applies as customary international humanitarian law (IHL) in both international armed conflicts (IACs) and non-international armed conflicts (NIACs), parties to an armed conflict must distinguish between the civilian population and combatants as well as between civilian objects and military objectives. Only combatants and military objectives may be targeted. This limitation is not so much due to the higher danger military objectives and combatants represent for the enemy, which is probably more afraid of nuclear scientists (who nevertheless belong to the civilian population) than of infantrymen. This limitation rather flows from the understanding that, if we want to have rules as well as restraints in war, violence should only be lawful if it is militarily necessary.
Already in 1868, the Saint Petersburg Declaration encapsulated this understanding, stating that “the only legitimate object which States should endeavour to accomplish during war is to weaken the military forces of the enemy.” IHL on the conduct of hostilities is thus a compromise between the competing principles of humanity and military necessity. Unnecessary military actions are always prohibited. In such cases, no compromise between military necessity and humanity is required.
This principle of distinction translates into the first restriction IHL imposes on any attack: it must be directed at a legitimate target, namely, a military objective, a combatant, a civilian while directly participating in hostilities or, at least in NIACs, a member of an armed group with a continuous combat function. Thus, attacks directed at any other target are, ipso facto, unlawful.
Second, even an attack directed against a legitimate target becomes unlawful if it violates the proportionality rule, which prohibits attacks that “may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.”
Third, even if an attack is conducted against a legitimate target and respects the proportionality rule, the attacking party must take all feasible precautionary measures in attack to avoid and, in any event, minimize incidental effects on the civilian population and civilian objects – effects that are not prohibited as such.
Fourth, in addition to the above principles that specifically protect the civilian population, IHL also limits the means (that is, weapons) or methods (that is, tactics) of warfare an attacking party may use, even when attacking legitimate targets. Such prohibitions and restrictions of certain weapons and tactics also benefit the civilian population, and some restrictions are even aimed exclusively at avoiding the effects of hostilities on the civilian population.
As all of these steps are cumulative, an attack is unlawful if it fails to satisfy even one of them.
Legitimate targets
Only combatants, military objectives, civilians while directly participating in hostilities and, arguably in NIACs, members of an armed group with a continuous combat function may be directly targeted.
- Military objectives and combatants
Combatants are obviously legitimate targets.
Whether an object may be targeted depends not so much on the intrinsic qualities of the object but on the prevailing circumstances at the time of the attack. Thus, an object may only be lawfully targeted if it satisfies two conjunctive elements at the time of attack: (1) it must effectively contribute by its nature, location, purpose or use to the enemy’s military action and (2) its destruction, capture or neutralization must offer the attacking party a definite military advantage. Indirect contributions are sufficient to satisfy the first element, as is only one of an object’s several functions if it concerns the enemy’s “military” action. Contributions to the so-called war effort, however, are insufficient.
The definition of who may be targeted is more restrictive than that of what may be targeted, although the latter is also very important for the protection of civilians as it is not unlawful to kill them incidentally when attacking a military objective if the proportionality rule is complied with and feasible precautionary measures to spare those civilians are taken.
An object must cumulatively meet two criteria to be a military objective. First, the targeted object’s “nature, location, purpose or use” must contribute effectively to the enemy’s military action. The list of an object’s possible contributions to enemy military action clarifies that not only objects of a military nature qualify as military objectives. “Nature” refers to the object’s intrinsic character. An operational tank, for example, is thus a military objective by its nature. “Location” indicates that a specific area of land may be a military objective. “Purpose” refers to the enemy’s intended future use, which must be based upon a reasonable belief. The U.S. even includes an object’s possible future use, but such an interpretation would leave very few protected civilian objects. “Use” refers to the current function of the object. For example, it is accepted that weapons factories and even extraction industries providing raw materials for such factories are military objectives because they support the military, albeit indirectly.
Second, and cumulatively, the object’s total or even partial destruction, capture or neutralization must also offer the attacking party a “definite military advantage” under the “circumstances ruling at the time.” A definite military advantage may consist of, for example, the attacker gaining ground or weakening the fighting ability of enemy armed forces.
Both conditions must be cumulatively fulfilled. Thus, although an attack aimed at capturing a food convoy destined to civilians may present the attacker with the military advantage of feeding its soldiers, it is nevertheless unlawful because the convoy does not contribute to the adversary’s military action.
By characterizing the necessary contribution as “effective” and the advantage as “definite” as well as by linking them to the “circumstances ruling at the time,” Article 52(2) of Protocol I avoids that everything can be considered a military objective by preventing parties from taking into account indirect contributions and possible future advantages. Allowing such considerations would otherwise permit parties to easily undermine the limitation of attacks to “military” objectives. Likewise, without the limitation to the actual situation at the time of an attack, the principle of distinction would be void as every object could become a military objective in the wake of possible future developments, such as a school being used by enemy troops.
Thus, what counts is that both the contribution to the enemy’s action and the advantage obtained from the attack must be “military.” The political aim of victory may be achieved only by weakening the military potential of the enemy through violence against military objectives. Indeed, if force could be used to achieve the political aim by directing it at any advantage and not just military objectives, the civilian population as such could be attacked, as they might very well influence the enemy government to surrender. Then, however, instead of IHL, there would merely be speculations about what could make the adversary surrender.
Another issue discussed in relation to military objectives is the status of dual-use objects, which are objects that serve both civilian and military purposes. Especially in times of war, the military uses civilian infrastructure, telecommunications and logistics for military purposes. Power-generating stations are crucial for civilian access to heating and clean water, but they also provide power to military communication systems and war industries in an integrated power grid. Computer hardware and software may be essential for military purposes, but it may be nearly impossible to identify technology actually destined or useful for those purposes. Dual-use objects, however, do not constitute a separate category in IHL. Rather, when a certain object is (or may reasonably be expected to be) used for both military and civilian purposes, even a secondary military use turns it into a military objective. However, an attack on a dual-use object may nevertheless be unlawful under the proportionality rule if civilians are excessively affected by the impact of the attack on the civilian use of the object.
- Civilians directly participating in hostilities
Civilians directly participating in hostilities may be targeted for the duration of their participation. The meaning of direct participation is controversial. It is suggested that the concept comprises the following cumulative elements. First, an act must be likely to adversely affect the military operations or military capacity of a belligerent or, alternatively, inflict death, injury or destruction on persons or objects protected against direct attack. Second, a direct causal link must exist between the act and the result. Third, that act must be specifically designed to directly cause the aforementioned harm in support of a party to the conflict and to the detriment of another.
In both IACs and NIACs, civilians lose their protection against direct attack as well as their protection against the incidental effects of attacks if and for such time as they participate directly in hostilities.
- Members of armed groups?
As combatant status does not exist in NIACs, it is suggested that members of an armed group fighting for a non-State party to a NIAC may be targeted at all times by analogy to combatants in IACs. Taking into account the factual differences between such groups and State armed forces in addition to the difficulties in identifying members of such groups, it is preferable to limit this analogy to members of an armed group with a continuous function to commit acts that constitute a direct participation in hostilities.
The proportionality rule
Even if directed against a legitimate target, an attack is prohibited if it may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated. It is unclear which factors count on both sides of the balancing test and how the comparison must be made.
The proportionality rule, which is applicable as customary law in both IACs and NIACs, prohibits an attack directed at a military objective that “may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.” Those incidental effects that may make an attack prohibited under this rule are often referred to as “collateral damage” by both the military and in common parlance. The “concrete and direct” qualifier indicates the anticipated military advantage should be both “substantial and relatively close” in time as opposed to advantages that are merely hypothetical or that would otherwise only manifest “in the long term.”
The proportionality evaluation must include possible reverberating (or cascading) effects. How far those effects must be taken into account remains, however, an open question. Based on its field experience, the ICRC launched a campaign to draw attention to the effects of urban warfare – effects that would exist to a certain extent even if only military objectives were targeted in cities. Basic health, water, sanitation and education infrastructure are heavily affected by urban warfare. Indeed, there may be a water pipe beneath a military objective or a power line next to it, and the destruction of either will have effects in other places of an urban area. The ICRC suggests that the cumulative effect of repeated attacks and the successive degradation of infrastructure must be taken into account.
Even apart from the question of reverberating effects and despite the qualifications of the anticipated military advantage as “concrete and direct,” it remains very difficult to compare a military advantage with civilian losses as such an evaluation inevitably involves subjective value judgments. This is especially true if, in addition, the actual probability of gaining the advantage and of affecting the civilian population is not 100 percent but different. Furthermore, the fact that the evaluation must be made ex ante from the perspective of the attacker, while the consequences of an attack are only known ex post, poses another difficulty in evaluating an attack’s compliance with this rule. Finally, the military’s obsession to keep their evaluation methods and plans secret, even once a conflict is over, presents another key challenge to any external evaluation of whether a given attack respected the rule.
In conclusion, although the proportionality rule is an important instruction for those who engage in attacks, its respect can only be evaluated in extreme cases given the challenges outlined above.
Precautions
The attacker and the defender must take all feasible precautions to avoid and, in any event, minimize the incidental effects of lawful attacks on the civilian population. The defender may not use human shields, while the attacker keeps its obligations in attack even if this prohibition is violated.
While an attack does not become unlawful merely because civilians and civilian objects are affected, IHL prescribes that both the attacker and the defender must take all feasible precautionary measures to try to avoid or at least to minimize an attack’s effects on civilians. The concepts of attacker and defender in this context have nothing to do with the jus ad bellum issue of who started the armed conflict but merely refer to the question of who is engaged in an act of violence in offence or defence as well as who is subject to that attack and has control over the civilian population to be protected.
- Active precautions to be taken by the attacker
Even when launching an attack that complies with the principle of distinction and the proportionality rule, an attacker must take all feasible precautionary measures to reduce its possible impact upon the civilian population, in particular by:
- Verifying that the target is in fact a lawful one under IHL;
- Warning the civilian population of the attack if possible;
- Cancelling or suspending an attack when “it becomes apparent” it will violate IHL; and
- Selecting the target (when a choice is possible between several targets offering a similar military advantage) as well as the means and method of warfare that may be expected to represent the smallest risk for the civilian population.
- Passive precautions to be taken by the defender
If possible from a legal, factual and humanitarian point of view, a defender must take feasible measures to protect civilians and civilian objects under their control against the effects of attacks, including by separating them from legitimate targets.
Article 58 of Protocol I provides that a defending party must take feasible precautionary measures to protect civilians against the effects of attacks against military objectives, such as removing the civilian population and civilian objects “from the vicinity of military objectives” and avoiding “locating military objectives within or near densely populated areas.” The wording of the provision, however, clearly indicates that these obligations are weaker than those of an attacker. All of the identified measures must be taken only “to the maximum extent possible,” and the defender is only required to “endeavour to remove” the civilian population and objects away from military objectives. The latter obligation is furthermore limited by a reference to the prohibition to forcibly transfer civilians in and from occupied territories in Article 49(1) of Convention IV.
- The prohibition against using human shields
It is prohibited to use civilians as human shields to “protect” legitimate targets.
Technically, the prohibition against using human shields is a free-standing prohibition and not a passive precautionary measure.
Article 51(7) of Protocol I reads: “The presence or movements of the civilian population or individual civilians shall not be used to render certain points or areas immune from military operations, in particular in attempts to shield military objectives from attacks or to shield, favour or impede military operations. The Parties to the conflict shall not direct the movement of the civilian population or individual civilians in order to attempt to shield military objectives from attacks or to shield military operations.”
It is important to note that the prohibition against using human shields covers only the “civilian population or individual civilians” and not civilian objects. Indeed, camouflage, which is not prohibited by IHL, effectively consists of making combatants and military objectives look like civilian objects and using civilian objects, such as barns and trees, for that purpose.
The decisive factor distinguishing the use of human shields from a mere violation of the obligation to take passive precautions is the intent, i.e. whether the defender’s intermingling of military forces and the civilian population aims at “protecting” its military forces and objectives or simply results from a lack of care for the civilian population.
- Consequences of a violation
An attacker must comply with its precautionary obligations in attack even when the defender does not comply with its own obligations to take passive precautions.
Specially protected objects
Specially protected objects benefit from a particular protection regime. They comprise medical material, cultural property, the natural environment, objects indispensable to the survival of the civilian population and works as well as installations containing dangerous forces. They may not be used for military purposes and even when so used do not necessarily turn into military objectives. The special protection regime protecting such objects prescribes additional considerations that must be accounted for in terms of distinction, proportionality and precautionary measures.
First, with the exception of material involved in peace operations, those who control specially protected objects may not use them for military purposes. Therefore, such objects should normally not become military objectives under IHL’s two-pronged test. Second, even if specially protected objects are actually used for military purposes and satisfy the test to become valid military objectives, they may only be attacked under restricted circumstances and only if the attacker complies with additional precautionary measures.
Cultural property is the most important category of protected objects. However, the wider issue of respecting and protecting cultural heritage in armed conflicts goes well beyond mere targeting issues and concerns equally the respect of objects in the power of a party and of persons involved in intangible cultural heritage.
Particular difficulties to establish violations of the IHL targeting rules
It is much easier to establish violations of protecting persons or objects in the power of a party (for example, whether a prisoner has been tortured, a person has been raped or a house in an occupied territory has been destroyed) than it is to determine violations of the targeting rules (for instance, whether a person killed or a school destroyed by an aerial bombardment constituted a violation of IHL). What counts for the targeting rules is not what was destroyed or who was killed or injured but what and who was targeted. To target civilians or civilian objects violates IHL and constitutes a war crime. Whether an attack is lawful does not depend on the results of the attack but rather an ex ante evaluation by the attacking party.
More generally, establishing whether an attack was lawful requires a complex analysis of several legal factors, including the status of the targeted person or object, whether such person or object was the actual target, the actual or intended use of the targeted object, the military value to the attacker in eliminating the targeted person or object in relation to the extent (if any) of expected incidental effects upon civilians and whether the attacker took all feasible precautionary measures in attack to avoid or minimize incidental effects upon civilians.
Assessing these legal factors necessarily requires knowledge of the military plans of both parties. Parties, however, do not make such information public and they do not have an obligation to do so. This unsatisfactory state of affairs could only be overcome if either transparency obligations were imposed upon both the attacker and the defender, or legal presumptions were stipulated based upon the results, which could be rebutted by the State prima facie responsible for a violation by explaining why the results do not correspond to the intent and the plans.
