The international Convention on Cluster Munitions, which was ratified in 2010, prohibits the use of these weapons for two main reasons: they have wide area effects and are unable to distinguish between civilians and combatants; and their use leaves behind large numbers of dangerous unexploded ordnance.
Despite 112 states signing up to the Convention, free trade persists among non-signatories, including the US, Saudi Arabia and India. The Pentagon issued its own cluster munitions policy in 2008, arguing that in certain missions submunitions warheads, as cluster munitions are officially dubbed, are more humane that unitary, non-submunition alternatives.
"Because future adversaries will likely use civilian shields for military targets - for example by locating a military target on the roof of an occupied building - use of unitary weapons could result in more civilian casualties and damage than cluster munitions," the policy states. "Blanket elimination of cluster munitions is therefore unacceptable due not only to negative military consequences but also due to potential negative consequences for civilians."
Despite this, the US Army is now looking for a replacement for one type of cluster munition, the Dual-Purpose Improved Conventional Munitions (DPICM). Lockheed Martin's Guided Multiple Launch Rocket System (GMLRS), given the US military designation M270, is the launch system for DPICM, as well as a number of unitary warheads. The new weapon would be a drop-in GMLRS-fired replacement for DPICM that has similar strike effects but without the negative drawbacks.
In April 2012, the US Department of Defense (DoD) awarded Lockheed Martin a US$79.4 million contract to lead the Alternative Warhead Program (AWP). AWP aims to engage the same types of targets and achieve the same area-effects but without leaving unexploded ordnance, which can injure or kill civilians years after the weapon was originally deployed.
Are modern variants being unfairly tarred with the same brush as their less reliable forbears?
Acting as a sub-contractor to Lockheed Martin, ammunitions specialist ATK has developed the new warhead, which designed to meet or exceed unexploded ordnance requirements, fit within the existing rocket architecture and concept of operations, and meet lethality and insensitive munitions requirements. While the DoD has confirmed AWP will be compliant with the provisions of the Convention on Cluster Munitions international treaty there is no specific clarification from Lockheed Martin or ATK in the latest programme updates whether this is a strictly unitary weapon.
The latest long-range test saw the AWP warhead fired from a HIMARS launcher and successfully destroy their respective targets approximately 65 km away, clearing the entry to the Developmental Test/Operational Test (DT/OT) phase, which incorporates soldiers into the system testing in autumn.
Thomas Nash is the director of Article 36, a London based NGO that looks at the humanitarian impact of weapons and encourages greater public scrutiny over the development of weapons and use of weapons. He is cautiously optimistic about the AWP.
"It's not clear to me whether this alternative warhead on the guided MLRS will have sub-munitions at all. From what I can see, it looks like what they're developing a unitary warhead," he says.
"In order to be compliant with the Convention On Cluster Munitions, which these articles say it would, if it does have submunitions they must a self-destruct fuse a self-deactivation fuse. They also have to have fewer than 10 warheads below a certain weight, and those sub-munitions need to independently select and engage individual targets."
There are only two submunitions weapons of which Article 36 is aware that comply with the convention. The SMArt 155 manufactured by GIWS mbh, a partnership between German armaments companies Rheinmetall and Diehl BGT Defence, and the BONUS, a French artillery shell which has two sub-munitions that each independently detect and engage targets.
But even if the new solution does not involve submunitions, would attempting to duplicate their effect raise similar human rights issues?
"The reason why we're concerned about cluster munitions and why states sought to prohibit them is first because they have a very wide area affect, and that made them difficult to target precisely" says Nash.
"While we wouldn't necessarily advocate a ban on explosive weapons that have a wide area effect, they are inappropriate for use in populated areas. A number of states - around 40 countries - have agreed that explosive weapons with wide area effects shouldn't be used in populated areas. The conflicts in Libya and Syria used older variants of the multiple-launch rocket system with absolutely devastating effect in populated areas."
Non-signatories to the convention put forward hypothetical scenarios on what cluster munitions were necessary, such as targeting a gun emplacement on a dam. If we used a unitary weapon we'd destroy the dam, they argued, but if we used a cluster munition we'd just get the gun.
"It's like saying is I can't use a stick to beat my child I'm going to have to use a hammer," says Nash. "Just because you can't use one thing because it's inappropriate, it doesn't mean you can use a worse thing."
Rejecting area effect
Putting the legitimacy of cluster munitions aside, the US military's interest in AWP may shine a light on the nature of modern conflicts, reflecting that the approach by which the US projects military force is not by saturating areas with area effect weapons.
"If you look at the direction people like [ISAF Commander] Stanley Allen McChrystal have taken the US military in Afghanistan, it's away from air strikes," says Nash. " It's challenging his commanders to do everything possible to avoid calling an air strike and bombing an area They want to withdraw, they want to return small arms fire if possible, they want to have more patrols."
However, as the conflict in Syria has demonstrated, the hands of rogue states will not be stayed by international law. The Assad administration has signed the Geneva convention, but is regularly flouting its rules. Syria has not signed Convention on Cluster Munitions and is using them to devastating effect.
But programmes such as AWP could at least suggest the start a new international movement away from cluster munitions.
"It's interesting to note that these munitions that are being developed for the US are seeking to comply with the Convention on Cluster Munitions which the US hasn't signed," says Nash. "That does suggest that it's having some sort of impact on the defence industry. That's a positive thing."