A/HRC/42/CRP.1 take general precautions so as to avoid unnecessary civilian casualties. 44 There is a general obligation on the defending party to protect the civilian population and civilian property from the effects of attack.45 There is a specific requirement that parties must, to the extent feasible, avoid locating military objectives in densely populated areas.46 This implies that the population is already present at the time the decision is taken as to where to locate the objective. There is also a specific requirement that civilians be moved away from military objectives, again “to the extent feasible”.47 Ways of discharging these obligations include evacuation, air raid warnings, ensuring an adequate supply of shelters and so on. In practice, it may be difficult to separate the civilian population and likely military objectives.48 If the objective cannot be moved, the only solution may be the evacuation of the population. If the party itself is not in a position to organize evacuation, the poor, the elderly and the sick and infirm are the groups likely to be particularly adversely affected. Whereas, in general, the party would be expected to put no barrier in the way of voluntary evacuation, where that is not possible, perhaps for security reasons, the party would be expected to provide adequate alternative facilities such as additional shelters. There is a general requirement of non-discrimination in international humanitarian law, reinforced by a non-derogable prohibition under human rights law. If one group in the civilian population under the control of the party in question is known to be less well protected than the rest of the population, this may raise issues of discrimination. 75. The attacking party is also required to take precautions both in planning and in carrying out an attack. Indiscriminate attacks are prohibited.49 That means attacks which are not targeted against a specific military objective.50 Furthermore, when determining how to carry out an attack against a military objective, a party is required to consider the foreseeable consequences of an attack on the civilian population and civilian property. Such a calculation cannot be made unless the party considers how, including with what weapon, it proposes to attack the objective. Attacks the foreseeable consequence of which is to give rise to excessive harm to civilians and civilian property by reference to the military advantage anticipated from the attack as a whole are also prohibited.51 An example of an attack which is disproportionate but not indiscriminate would be an attack which is targeted against a specific military objective but where the foreseeable harm caused is much greater than the military advantage to be gained. By changing the proposed weapon or the proposed tactic for an attack, it may be possible to reduce the foreseeable impact on civilians (“collateral damage”) to such an extent as to make the attack lawful. It should be emphasized that the fact of civilian casualties alone does not mean that an attack was unlawful. In order for a high civilian toll to be evidence of an unlawful attack, it is necessary to establish that civilians were the target or that an attack was indiscriminate or that the foreseeable casualties were excessive in relation to the military advantage anticipated. 76. The principle of proportionality not only has to be given effect in the planning of an attack but at all times during the conduct of an attack. In other words, if it becomes clear during the conduct of an attack that the circumstances or the consequences are not what they were thought to have been and the attack would give rise to excessive civilian harm, the attack must be cancelled or suspended.52 Further, precautions in attack require a party to 44 In an armed conflict, each party is both attacker and defender, depending on the context. The use of attacking and defending does not relate to the party which started the armed conflict but refers to their role in the particular situation under consideration. 45 See generally ICRC Study on customary IHL, rule 22. 46 ICRC Study on customary IHL, rule 23 47 ICRC Study on customary IHL, rule 24. 48 There are circumstances where the location of a military objective is clearly a matter of deliberate choice as when, during the 1991 Gulf War, an Iraqi military airplane was located in the middle of historic ruins. 49 See generally ICRC Study on customary IHL, rule 11. 50 ICRC Study on customary IHL, rule 12. 51 ICRC Study on customary IHL, rule 14. 52 ICRC Study on customary IHL, rule 19. 19