Recent armed conflicts have demonstrated the devastating humanitarian impact of using explosive weapons with wide-area effects in populated areas.

This is due not only to the direct blast and fragmentation effects of using such weapons in populated areas, but also because of the ‘reverberating effects’ of such an attack, meaning those effects that are not directly caused by the attack, but are nevertheless a product thereof.

Notably, incidental destruction of civilian housing and essential civilian infrastructure – which often leads to a disruption of essential services – can result in civilian death and injury that may far outweigh the immediate civilian casualties caused by an attack.

Under the IHL rules on the conduct of hostilities, “incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof” (hereafter: incidental damage) must be assessed and taken into account when launching an attack. The rule on proportionality and the obligation to take all feasible precautions in attack both require an assessment of the incidental damage that is expected to result from an attack.

In interpreting and applying these rules, it is increasingly accepted – by the ICRC, as well as by a growing number of States and commentators – that attacking parties must take into account the foreseeable reverberating effects of the attack. Accordingly, commanders are obliged to not only assess the direct incidental damage that may be expected from an attack, but must also consider the foreseeable reverberating effects of the attack.

Even though this position enjoys support from a number of States and commentators and is included in the military manuals of some States, uncertainties linger as to the scope of the obligation. For instance, it has been debated whether there is a causal, temporal or geographical limit to the reverberating effects that need to be considered. Some commentators (.pdf) have disputed the relevance of reverberating effects on the grounds that there are “too many factors that are incapable of assessment at the time the attack.”


‘Reasonable foreseeability’

These concerns are arguably addressed by the threshold of reasonable foreseeability, which is an objective standard that can be inferred from the text of the relevant rules (“may be expected”). Reasonable foreseeability means that attacking parties must take into account the reverberating effects that would be foreseeable to a reasonable commander, taking into account the information reasonably available at the time of the attack.

While incorporating an objective element, the assessment of incidental damage is also context-dependent, as proportionality is assessed ex ante and not with the benefit of hindsight. In some cases, the specific context of the attack means that certain reverberating effects may be objectively foreseeable, such as in the case of repeated or cumulative attacks against a populated area.

For instance, if a commander is or should be aware that essential civilian infrastructure (for example, hospitals, water and electricity infrastructure) has been partially damaged leading to a disruption of essential services, it is reasonably foreseeable that any future incidental damage to such infrastructure will have a more significant impact on the civilian population, including a higher likelihood of indirect civilian casualties.

Likewise, in protracted conflicts, it is reasonably foreseeable that the quality of essential services will have degraded, due to inability to ensure proper maintenance of infrastructure. As a result, it may be reasonably foreseeable that the reverberating effects of damage to civilian infrastructure will also have a more significant impact on the civilian population.

Conversely, the context of an attack can limit the foreseeability of certain reverberating effects, as the information that is reasonably available to the commander may be limited.  A commander directing an attack in response to incoming fire to save the lives of own troops might not be expected to engage in intelligence gathering to the same extent as in a pre-planned attack.

Indeed, pre-planned attacks allow for more time to consult with technical experts (engineers, medical professionals, etc.) regarding the reasonably foreseeable reverberating effects of the attack, which may not be possible when responding to incoming fire. Importantly, this does not absolve the commander engaged in such attack from taking into consideration those reverberating effects that are reasonably foreseeable, based on the available information. Moreover, relevant technical information and expertise, particularly regarding the location of civilian infrastructure and the reverberating effects of damaging such infrastructure, might already have been fed into the preparations for the broader operation and would still be relevant when using explosive weapons in response to incoming fire.

While recognizing that no case is identical, past experiences and empirical data may also contribute to making certain reverberating effects reasonably foreseeable. For instance, the increasing experience of armed forces in urban combat and greater awareness in the public domain about the interconnectedness of essential services arguably makes it objectively foreseeable that damage to or destruction of essential infrastructure will have certain reverberating effects on essential services, such as health care and water distribution.

Similarly, recent conflicts have shown that when explosive weapons with a large destructive radius, an inaccurate delivery system, or the capacity to deliver multiple munitions over a wide area, are used in populated areas, there is a high likelihood that civilians will be killed and injured, and essential civilian infrastructure will be damaged or destroyed, with consequent disruption in essential services, and subsequent effects on the lives and wellbeing of the civilian population.

Proportionality and precautions in attack

The obligation to take into account the reasonably foreseeable reverberating effects of an attack is reinforced by the precautionary obligation to refrain from launching a disproportionate attack, which imposes a duty to proactively gather information that will inform the assessment of the expected incidental damage of the attack. But what does this require in practice, particularly in relation to the reverberating effects of attacks in populated areas using explosive weapons with wide-area effects?

In some cases, commanders may be required to obtain information relating to the location and interconnectedness of essential civilian infrastructure and supply networks, including primary infrastructure (e.g. water distribution networks, water treatment plants, electricity generating plants) as well as secondary and tertiary infrastructure (e.g. transmission lines or sub-transformers). As mentioned above, it may also be necessary to incorporate technical expertise into targeting processes, in order to ensure that the reasonably foreseeable reverberating effects of the attack can be adequately assessed.  Whereas the operational context might impact the extent to which a commander is expected to proactively gather information to inform the estimation of incidental damage, a commander may never ignore reasonably available information, including such information that renders the reverberating effects of an attack reasonably foreseeable.

Additionally, the IHL rule on precautions obliges attacking parties to take all feasible precautions in the choice of means and methods of attack, with a view to avoiding or minimizing the expected incidental damage, including the foreseeable reverberating effects of the attack. Compliance with this obligation will of course depend on the particular context, but will require assessment of the foreseeable effects of the available weapon systems, in view of their technical characteristics and the expected circumstances of their use – for instance, the timing, angle and location of the attack, as well as the type of fuse and type/size of the warhead.

That said, while precautionary measures such as adjusting the technical features of the explosive weapon might be feasible and could minimize the expected incidental damage of an attack, these precautions might not suffice to obviate the wide area effects of certain explosive weapons when used in populated areas. In such cases, if its use may be expected to lead to a violation of the prohibition of indiscriminate or disproportionate attacks, the only option may be to refrain from using the weapon.


The extensive civilian harm witnessed in recent armed conflicts underscores the importance of giving due weight to the reasonably foreseeable reverberating effects of an attack in applying the rules on proportionality and precautions in attack. This is particularly crucial where explosive weapons with wide area effects are used in populated areas. As is currently the case for some militaries, policy guidance should be put in place to identify which kinds of precautions in attack can and should be implemented, in order to assess and minimise the reverberating effects of an attack using explosive weapons with wide-area effects in populated areas.

Likewise, when it is reasonably foreseeable that using a particular explosive weapon in a populated area will result in excessive incidental civilian harm, military manuals and policy should set out clear restrictions on the use of those weapons in populated areas. Although it is not possible to foresee and limit all of the possible effects of an attack, a lot more can be done to better understand the reverberating effects of an attack using explosive weapons with wide-area effects in populated areas and to develop policy guidance and concrete measures to enhance the protection of civilians against such effects.


Recommended reading

  • I Robinson and E Nohle, “Proportionality and Precautions in Attack: The Reverberating Effects of Using Epxlosive Weapons in Populated Areas”, International Review of the Red Cross, forthcoming
  • M Zeitoun and M Talhami, “The Impact of Explosive Weapons on Urban Services: Reverberating Effects across Space and Time”, International Review of the Red Cross, forthcoming