Cluster munitions are weapons that include cargo containers and submunitions. The cargo containers are fired, launched or dropped by aircraft or land-based artillery. The containers open over a target area and disperse large numbers of the submunitions that are designed to explode when they hit the target. Most of these submunitions are fragmentation weapons that include a shaped charge so that they are effective against soldiers as well as armoured vehicles. The vast majority of cluster munitions contain hundreds of submunitions that are unguided and that cover one square kilometre with explosions and shrapnel.

Cluster munitions pose a problem for civilians during attacks because they cover such a wide area with explosions and shrapnel. The ‘footprint’ of a cluster munition can be one square kilometre. This means that when they are used in or near populated areas they cannot distinguish between military targets and civilians located within that footprint. Most modern conflicts have involved considerable fighting within urban settings. Most modern military forces include cluster munitions as a major component of their war fighting strategy. This means that cluster munitions are likely to cause serious problems for civilians during future conflicts.

This is not the only problem cluster munitions pose. Because of the large number of submunitions in each weapon as well as the number of submunitions that fail to explode as intended, areas bombarded with cluster munitions become contaminated with unexploded ordnance. These unexploded submunitions can explode when children pick them up and play with them, they can explode when people hit them with a tool while farming and sometimes they are sensitive enough to function like a landmine. The presence of such unexploded submunitions puts lives and livelihoods at risk for a long time after a conflict.

No treaty covers cluster munitions specifically. Other weapons with indiscriminate effects, such as landmines and firebombs, are the subject of specific rules that complement and reinforce the general rules of international humanitarian law applicable in armed conflict. Because of their wide area effects and the large numbers of unexploded ordnance they leave after a conflict, many groups, such as the International Committee of the Red Cross, have called for specific rules on cluster munitions.

Most countries have strongly opposed the development of new rules on cluster munitions because they say the existing rules are enough. However, if international humanitarian law is adequate and armed forces are implementing it then why is there such a humanitarian impact of cluster munitions whenever and wherever they are used? NGOs have argued that if you’ve got a problem and you have a law that is supposed to stop it, but you still have a problem then something is either wrong with the law or wrong with the implementation of the law.

In any case, new rules on cluster munitions would reinforce the existing rules that apply to all weapons. Cluster munitions pose specifc problems under the following three rules of customary international humanitarian law to which all parties to all conflicts must adhere:

Distinction – this rule prohibits indiscriminate attacks. Indiscriminate attacks are attacks that are not directed at a specific military objective; attacks that use weapons that cannot be directed at a specific military objective; and attacks that use weapons whose effects cannot be limited and that strike civilian as well as military objectives. Indiscriminate attacks are also attacks that treat distinct military targets located in populated areas as one target, the clear example being the carpet-bombing of large cities during WWII.

Proportionality – this rule means that the concrete military advantage gained from an attack must be greater than the damage to civilians foreseeable at the time of the attack. It is a complicated rule that is interpreted differently by different armed forces.

Feasible precautions – this rule means that all feasible precautions must be taken to minimise incidental loss of civilian life, injury to civilians and damage to civilian objects. This includes warning civilians about the threat of unexploded submunitions.