A/HRC/2/7 page 8 Convention), and those provisions of the Additional Protocol I that are declaratory of customary international law. While the qualification of the conflict as international or non-international is complex, this report is mainly based on international customary law applicable in both forms of conflict. 24. Of the rules applicable to attackers, the most relevant relate to the principle of distinction, the principle of proportionality, and the obligation to take precautionary measures. These obligations are cumulative: an attack must comply with all of the rules in order to be lawful. 25. First, under the principle of distinction, the parties to a conflict must at all times distinguish between civilians and combatants,23 and attacks may be directed only at military objectives, defined as those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage.24 The only circumstance in which civilians may be targeted is for such time as they take a direct part in hostilities.25 Thus, attacks on civilian objects26 are unlawful unless at the time of the attack they were used for military purposes and their destruction offered a definite military advantage. 26. Indiscriminate attacks are similarly prohibited.27 They are those which (i) are not directed at a specific military objective; (ii) employ a method or means of combat which cannot be directed at a specific military objective; or (iii) employ a method or means of combat the effects of which cannot be limited as required by international humanitarian law; and consequently, in each such case, are of a nature to strike military objectives and civilians or civilian objects without distinction.28 Attacks by bombardment, including with rockets, which treat as a single military objective a number of clearly separated and distinct military objectives located in an urban area or rural village are prohibited.29 The prohibition of indiscriminate attacks must not only determine the strategy adopted for a particular military operation but also limit the use of certain weapons in situations where the civilian population will be affected. 27. Second, under the principle of proportionality, attacks on legitimate military objectives which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated, are prohibited.30 28. Third, an attacker must take all feasible precautions to avoid, and in any event to minimize, incidental loss of civilian life, injury to civilians and damage to civilian objects.31 A number of specific precautionary measures are prescribed by humanitarian law in relation to the planning and conduct of attacks.32 In addition, an attacker is required to give effective advance warning of attacks which may affect the civilian population, unless circumstances do not permit.33 29. International humanitarian law also imposes obligations on defenders. The use of human shields is prohibited.34 Violation of this rule may be understood to require the defender’s specific intent to use civilians to immunize otherwise legitimate military objectives from lawful attack.35 In addition to this prohibition, the defender also has affirmative obligations to protect civilians by keeping them away from military targets.36