The rules of targeting of international humanitarian law play a pivotal role in protecting civilians. They achieve this by requiring military commanders to take appropriate steps when planning and executing military operations to mitigate danger to civilians. Yet, there is little guidance on how parties to the conflict apply the rules of targeting on the battlefield. Consequently, the task of Non-Governmental Organizations to hold parties to the conflict to account for breaches of the rules is extremely difficult. In the course of studying state practice on the rules of targeting I identified a number of trends which capture how commanders in all likelihood apply the rules of targeting to battlefield scenarios. A number of the findings challenge conventional views. This points to the fact that the debate concerning the rules of targeting continues to be necessary even though one can model how commanders apply the rules. I would like at this stage to share with you some of the conclusions I arrived at.

The principle of distinction requires attackers to distinguish at all times between civilians and combatants on the one hand, and civilian objects and military objectives on the other hand. The conventional view is contained in publications, such as the “Commentary to the Humanitarian Policy and Conflict Research Manual on Air and Missile Warfare.” It postulates that the degree of certainty the principle of distinction requires attackers to achieve is less than that entailed by the criminal law standard of proof of “beyond reasonable doubt.” However, it is concluded that the degree of required certainty is higher. The elements of available intelligence, urgency of acting, force security and the civilian harm which will result if the target is misidentified should each individually reinforce the conclusion that the target is a military objective in order for the attacker to be entitled to engage the target.

The rule of target verification requires the attacker to do everything “feasible” to verify that a chosen target is a military objective. Ian Henderson in his book “The Contemporary Law of Targeting: Military Objectives, Proportionality and Precautions in Attack Under Additional Protocol I” submits that the consideration of how many civilians will be killed if the target is misidentified and the likelihood of the target being a civilian object should play a role in a commander’s assessment of whether he or she is doing everything “feasible” to verify that the target is a military target. The examination of state practice reveals that commanders indeed balance the elements of the likelihood of harm to civilians occurring and the military advantage entailed in conducting further reconnaissance in assessing whether it is “feasible” to allocate additional resources to verifying the character of the target. They may additionally for policy reasons consider the number of civilians who will die if the target is mistakenly identified as having military character. The obligation to comply with the principle of distinction is one of the reasons why commanders do not view the magnitude of potential civilian harm as a core component of the rule of target verification. I was able to derive propositions capturing when commanders are likely to give greater weight either to the likelihood of civilian harm or to particular military considerations, such as the urgency of engaging the target.

Turning to the principle of the least feasible damage, the rule admonishes attackers to take all “feasible” precautions in choosing weapons and tactics with a view to avoid, or to minimise, harm to civilians. State practice reveals that when considering what weapons and tactics it is “feasible” to employ in order to reduce danger to civilians, commanders balance three elements. Using urban combat as a common scenario and the data about the extent of casualties different weapons produce I derive various propositions for how commanders apply the principle of the least feasible damage. For instance, a commander may need to use a weapon that causes less harm to civilians than an alternative if the element of military advantage exceeds by one unit of measurement the element of magnitude of harm to civilians, provided that there is a “high” likelihood of civilian harm materialising. What is more, the attacker may be obligated to take greater care in selecting weapons and tactics when operating close to civilian objects that house vulnerable groups. The scrutiny of state practice confirms that an attacker is under an obligation to assume risk to the force in choosing weapons and tactics.

Commanders are additionally obligated to issue an “effective” advance warning of the attack “unless circumstances do not permit.” The field of psychology is arguably valuable for understanding how commanders deliberate whether circumstances permit an advance warning of the attack to be issued to civilians. Resort to other disciplines is necessary because it is difficult to analyse the practice of states on the application of this rule in terms of the component elements of the rule, namely in terms of the likelihood of harm to civilians, the magnitude of harm to civilians and military advantage. The use of the field of psychology provides startling insights into military decision-making. For example, the application of the concept of “psychophysical numbing” in psychology points to the fact that in determining whether circumstances permit an effective advance warning to be issued, the commander may give greater consideration to the plight of civilians if the warning were to reduce the deaths in a small town from 200 to 100 than if the warning were to decrease deaths in a large town from 2000 to 1900. Moreover, the personality of the commander and his or her emotional state is likely to influence the assessment concerning the permissible level of harm to civilians. Clearly, there is a need for consistent decision-making and hence for a greater awareness of how individual characteristics of the commander influence his or her assessment. The full findings appear in my book “A toolbox for the application of the rules of targeting.”