What is a barrel bomb?
As recently analysed in a very knowledgeable blog entry by the warhead consultant Richard M. Lloyd, barrel bombs used in Syria normally consist of a cylinder – which can be an oil barrel and probably gave the bomb its name – filled with an explosive and metal pieces. It is also reported that more recent versions of these ‘do it yourself’ crude weapons were filled with fuel, and constructed in a way that resembled them to ‘fuel air explosives’ with geographically wide and significant destructive effects. Earlier on in the conflict, smaller versions of these bombs rolled out of helicopters at low altitude, which enabled the Syrian army to aim the bomb at specific targets. In contrast, probably due to improved capacity of opposition forces to target helicopters at low altitude, barrel bombs are increasingly dropped from helicopters at altitudes up to 2000m. In the armed conflict in Syria, barrel bombs provide a way to cause ‘cheap and lethal damage on urban areas’.
The legality of the use of barrel bombs under international humanitarian law
Under IHL, a weapon can be absolutely prohibited as an unlawful means of warfare, or the use of these weapons can be illegal in specific circumstances. Barrel bombs would be absolutely prohibited if they were inherently indiscriminate, meaning they cannot be targeted at a military objective. While this may be the case when released from high altitude, this is not necessarily the case when dropped from low altitude where it seems possible to direct the barrel at a specific military target. Thus, these bombs are not inherently indiscriminate.
The questionable argument has been made that barrel bombs are incendiary weapons the use of which against civilians or military objectives located within a concentration of civilians violates the UN Convention on Certain Conventional Weapons. To be clear, the UN Convention on Certain Conventional Weapons does not apply in Syria because Syria is not a party to it. Still, restrictions on the use of incendiary weapons exist under customary international law. However, in their common form barrel bombs do not appear to fall under the definition of incendiary weapons under customary international law – unless allegations are true that some of these bombs were filled with napalm and primarily designed to set fire to objects or to cause burn injury to persons.
Barrel bombs have also been condemned as weapons that spread terror among the civilian population. Aerial bombardments, especially in neighbourhoods where civilians are present, give rise to a degree of fear and terror among the population. What would make the use of barrel bombs illegal, however, would be if the primary purpose of their use was to spread terror among the civilian population. This is particularly the case when such weapons are used without producing a military advantage. While this may be the case in some situations in Syria, it might be difficult to show that spreading terror is their primary purpose.
Instead of resorting to strong terms such as ‘incendiary weapons’ and ‘terror’, reference to fundamental rules of customary IHL provides a prohibition of the use of barrel bombs in the present circumstances. First, it is clear that the use of these bombs is prohibited when they are directed against civilians or civilian objects. But even if it was not possible to show that the Assad regime is targeting civilians and not opposition fighters thought to operate from civilian neighbourhoods, dropping barrel bombs on predominately civilian areas from high altitude undoubtedly constitutes a prohibited indiscriminative attack. Due to the crude nature of barrel bombs, when used in predominantly civilian neighbourhoods they cannot be directed at a specific military target and their use is therefore prohibited.
Does the use of barrel bombs constitute a war crime?
If hopefully one day the International Criminal Court, a Syrian national court, or an international(ized) or regional tribunal adjudicates over alleged war crimes committed by all parties to the Syria conflict, the question will arise whether the use of barrel bombs constituted a war crime. War crimes under article 8(2)(e) Rome Statute provide only a limited criminalization of such attacks. Indiscriminate attacks are not explicitly criminalized under the Rome Statute. In order to constitute a war crime, it would need to be proven that the attack was intentionally directed against the civilian population. In this respect, the ICTY argued that ‘indiscriminate attacks, that is to say, attacks which strike civilians or civilian objects and military objectives without distinction, may qualify as direct attacks against civilians’. In addition, the Rome Statute does not provide an exhaustive list of war crimes. The ICRC finds that under international law applying in internal armed conflicts there is sufficient basis to conclude that ‘launching an indiscriminate attack resulting in death or injury to civilians’ constitutes a war crime.
To sum up, despite their crude nature and the clear difficulty to direct these bombs at military targets, barrel bombs are not absolutely prohibited under IHL. In fact, if the Assad regime used these bombs in circumstances where it was able to target them at military objectives, the use of these bombs would not necessarily be prohibited. However, reports unanimously suggest that barrel bombs are currently intentionally directed at civilian neighbourhoods or dropped from high altitudes in a way that makes it impossible to direct these bombs at military targets. In both circumstances, this constitutes a clear violation of the laws of war, and could amount to war crimes. As a result, it is not the bomb as such that contravenes international rules on armed conflicts, but it is the way Syrian forces employ this weapon that violates IHL, and likely constitutes a war crime.