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Attention will now turn to scrutinizing how Ukraine deploys the US weapons. 

On 7 July, days before the NATO summit in Vilnius, the US announced that it would supply Ukraine with cluster munitions – until it can ramp up production of other types of ammunition.

It is a controversial decision which is at odds with the views of NATO allies that have foresworn the possession and use of the weapons under the 2008 Convention on Cluster Munitions.

The Biden administration said it had received assurances from Ukraine that the munitions will not be used in areas populated by civilians, that Ukraine will keep records and maps of where they are used, and that it will conduct a post-war clean-up.

However, there are significant humanitarian concerns with the use of cluster bombs, and the US–Ukraine decision sends the wrong message to the wider world – particularly to states that are not yet parties to the 2008 Convention.

Humanitarian concerns

Each cluster bomb can scatter tens or hundreds of explosive submunitions over a wide area.

The submunitions frequently do not explode on delivery – this is called the failure rate – and are left in the environment, often sinking into soft ground or water. In recent conflicts, failure rates remain stubbornly high, estimated to range from 10%-40% – despite being much lower in the testing phase.

The long-term implications of failed submunitions have been similar to – in some cases worse than – the long-term use of anti-personnel landmines.

Munitions surface years or even decades after use, often picked up by children who mistake them for soda cans or toys and are maimed or killed when they explode. Whether the munitions have been fired by an enemy or by their own side, the effect is the same.

The use of the weapons also risks breaking international humanitarian law, namely the principle of distinction (the need in an armed conflict to distinguish between combatants and civilians; and between military and civilian objectives).

Concerns also relate to breaching the principle of proportionality, and the rule against indiscriminate attacks.

The 2008 Convention on Cluster Munitions (CCM)

The CCM is an important piece of international law intended to prohibit the use of cluster munitions in line with these principles of international humanitarian law, placing the long-term needs of civilians at the heart of security decision-making.

To date, the CCM has 111 states parties, and 12 signatories. It prohibits the use, production, transfer, and stockpiling of cluster munitions. It requires countries that have joined the convention to destroy their stockpiles of the weapons, clear areas contaminated with unexploded submunitions, and provide assistance to victims.

The US, Ukraine and Russia have not yet signed up to the convention. Neither has China or India. But most European states have joined the treaty, including NATO members such as the UK, Germany and France.

The convention drew upon experience from the Mine Ban Treaty of 1997 which prohibited the use, stockpiling, production and transfer of anti-personnel mines. Following the treaty, deminers reported the equally large problem of other unexploded ordnance including cluster munitions.

This empirical evidence, along with medical evidence from countries inundated with cluster munitions such as Cambodia, Kosovo, Iraq, Chechnya, Eritrea, Ethiopia and Afghanistan, led to discussions in the Convention on Certain Conventional Weapons and then to a stand-alone process that negotiated the Convention on Cluster Munitions. 

Indeed, the conclusion of the Convention on Cluster Munitions and its support by so many countries had until now created an important pause in the use of cluster munitions by some non-states parties, including the US – showing the weight of international condemnation of the weapons. (This has not been true for countries such as Russia which has used them with devastating effect against civilians in Ukraine).

Cluster munitions are already being used in Ukraine

Russia has been using cluster munitions throughout its illegal war against Ukraine, along with landmines and thermobaric/vacuum weapons. It has also threatened the use of nuclear weapons. Ukraine has also used its own ex-Soviet stockpile of cluster bombs.  

But up until now no NATO country has supplied Ukraine with cluster bombs – reports that Turkey had done so have been denied by both Turkey and Ukraine.

Supporters of the US decision point out that the number of unexploded US cluster munitions will be far smaller than the equivalent number of unexploded Russian munitions and landmines already in Ukraine.

They also argue that the numbers of Ukrainian civilians killed might well be far higher if Ukraine fails to pursue its counteroffensive, and that Ukraine could even lose the war if not supplied with adequate ammunition.

Adhering to the rules of war

Russia’s invasions of Ukraine in 2014 and in 2022 were illegal. Subsequent threats to use nuclear weapons, and the continuing situation over the Zaporizhzhia nuclear power plant, have been reckless in the extreme.

Russia’s actions reflect the fact that the war is not only about the integrity and sovereignty of Ukraine – although that is of course central. It is also about values, and the adherence to the rule of law.

How a state conducts itself during a war is important. Irrespective of the aggression by Russia, and regardless of who has joined the Convention on Cluster Munitions, the rules of international humanitarian law must be respected by all parties to the armed conflict.

These rules are designed to balance military necessity with humanitarian purpose – they seek to protect civilians and diminish unnecessary suffering. Ukraine is fighting not just for its territory but for the international rule of law; its own conduct of hostilities must comply with the rules of war.

Attention will now need to turn to scrutinizing how Ukraine deploys the US weapons and whether it can live up to its assurances on how they will be used, including preventing their deployment in or near civilian populated areas.

States that are party to the CCM should continue to uphold it. The UK and other treaty members have invested significant diplomatic power to encourage other states to accede to the CCM and they should continue these efforts. The US move sends a poor message, but the fundamental importance and value of the CCM treaty remains.