A/HRC/12/48 page 131 529. The determination of whether the circumstances permit a warning must be made in the context of a good-faith attempt to adhere to the underlying duty to minimize death and injury to civilians or damage to civilian objects. The key limitation on the application of the rule is if the military advantage of surprise would be undermined by giving a warning. The same calculation of proportionality has to be made here as in other circumstances. The question is whether the injury or damage done to civilians or civilian objects by not giving a warning is excessive in relation to the advantage to be gained by the element of surprise for the particular operation. There may be other circumstances when a warning is simply not possible. 530. Article 57 (2) (c) requires the warning to be effective. The Mission understands by this that it must reach those who are likely to be in danger from the planned attack, it must give them sufficient time to react to the warning, it must clearly explain what they should do to avoid harm and it must be a credible warning. The warning also has to be clear so that the civilians are not in doubt that it is indeed addressed to them. As far as possible, warnings should state the location to be affected and where the civilians should seek safety. A credible warning means that civilians should be in no doubt that it is intended to be acted upon, as a false alarm of hoax may undermine future warnings, putting civilians at risk. (a) Pre-recorded generic telephone calls 531. As regards the generic nature of some pre-recorded phone messages, the Mission finds that these lacked credibility and clarity, and generated fear and uncertainty. In substance, there is little difference between telephone messages and leaflets that are not specific. The Mission takes the view that pre-recorded messages with generic information may not be considered generally effective. (b) Warning shots delivered to roofs 532. The Mission is doubtful whether roof-knocking should be understood as a warning as such.365 In the context of a large-scale military operation including aerial attacks, civilians cannot be expected to know whether a small explosion is a warning of an impending attack or part of an actual attack. In relation to the incident at the Sawafeary house recounted above, the Mission cannot say for certain if this missile was meant to warn or to kill. It notes that, if this was meant as a warning shot, it has to be deemed reckless in the extreme. 533. The legal requirement is for an effective warning to be given. This means that it should not require civilians to guess the meaning of the warning. The technique of using small explosives to frighten civilians into evacuation, even if the intent is to warn, may cause terror and confuse the affected civilians. 534. The Mission does not have sufficient information to assess the accuracy of the Israeli Government’s claim that the warning shot method was used only when previous warnings (leaflets, broadcasts or telephone calls) had not been acted upon. However, in many circumstances it is not clear why another call could not be made if it had already been possible to The Mission notes and agrees with a similar position set out by Diakonia in its report on Operation Cast Lead of 30 June 2009, p. 9. 365