What are Cluster Munitions?

M42/M46 submunition. An M483A1 155mm projectile contains 64 M42 and 24 M46 submunitions. Photo: DanChurchAid/Jawad Metni

Cluster bombs, or cluster munitions, are weapons containing from several to hundreds of explosive submunitions. They are dropped from the air or fired from the ground and designed to break open in mid-air, releasing the submunitions and saturating an area that can be as wide as several football fields.

Cluster munitions are area-effect weapons: their impact is not limited to one precise target such as an individual tank. Instead, a whole area is scattered with explosives. At the time of use, anybody within the targeted area is very likely to be killed or seriously injured. Since the explosive submunitions are not precision-guided, not directed against a specific military object, their accuracy can be affected by weather and other environmental factors. Most cluster munitions therefore hit areas outside the military objective targeted.

History shows that the reliability rate of cluster munitions is very low. Many of the submunitions fail to explode as they are supposed to, leaving huge quantities of unexploded ordnance on the ground. After the attack, these unexploded submunitions remain, like landmines, a fatal threat to anyone in the area.

The definition of cluster munitions found in the new Convention on Cluster Munitions constitutes the first legal definition of this weapon in international law. It covers all weapons with explosive submunitions and places a prohibition on this entire category of weapons.

The Convention on Cluster Munitions defines the weapon as 'a conventional munition that is designed to disperse or release explosive submunitions each weighing less than 20 kilograms, and includes those explosive submunitions.'

The definition makes certain clarifications for weapons that have submunitions but are not considered cluster munitions, such as weapons with submunitions designed for smoke, flare, and electronic counter-measures. Also falling outside the definition are weapons that have submunitions but that do not cause the same indiscriminate area effects or UXO risks as cluster munitions. Such munitions must meet each of a series of five minimum technical characteristics set out in the convention.