When the war in Ukraine was only a few months old, Amnesty International published a report condemning what it had found to be the extensive use of cluster munitions in Kharkiv – by Russia. It noted that the weapons were banned by more than 100 countries and said that in Kharkiv they had claimed hundreds of civilian victims. Cue accusations of war crimes and western outrage against Russia’s uncivilised way of war.

Now, a few days before the Nato summit convenes in Vilnius, President Biden has announced that the US will deliver similar weapons to Ukraine. Recognising that this was going to be a controversial decision, he cited conditions and safeguards agreed for their use, before offering what was clearly intended to be the clinching argument: that ‘the Ukrainians are running out of ammunition’. The unspoken challenge to doubters was: do you really want to be complicit in Ukraine losing this war?

If cluster munitions are some sort of last resort, then Ukraine is in a double bind

Now it is only fair to point out that no laws or conventions are being broken here. The US is not a signatory to the 2008 Convention on Cluster Munitions and neither is Ukraine – nor Russia, for that matter. To that extent, the US is within its rights to provide these weapons, although Biden has had to waive certain US domestic restrictions on their transfer.

The ethics of the decision and what today is called the ‘optics’, on the other hand, are another matter, as is what this development might reveal about the state of the war. Cluster munitions are banned by many countries – including the UK and most EU members – for a reason. They are more indiscriminate than conventional shells and are liable to misfire and leave unexploded bomblets scattered over a wide area. These may then become lodged in the ground and lie undetected until disturbed by unwary civilians, especially children.

Of course, the same characteristics, including the capacity to cause more damage over a wider area than other munitions, allow the user to, crudely put, get more bang for their buck. It also helps to explain why they may be attractive to a combatant in particular types of warfare and why the US and some other countries have avoided restricting their room for manoeuvre by signing the international convention.

At its most basic, the US argument boiled down to this: Ukraine has been asking for these weapons, it needs them, we have plenty of them, so it makes sense to release them as a ‘bridging’ measure before other stocks are available. But the way the decision was announced, which included extensive trailing in the international media beforehand, showed that the US administration was braced for the international opprobrium that duly came.

Biden said it had been a very difficult decision and that he had thought long and hard before he he had been persuaded. He also said that Ukraine had given undertakings about how and where they would use the cluster munitions, avoiding civilian areas and keeping records to facilitate a thorough clean-up operation once the conflict was over. There was also an attempt by the National Security Adviser, Jake Sullivan, to present US cluster munitions as less lethal to civilians than those used by Russia, on the basis of comparative figures for the so-called ‘dud’ rate, which came perilously close to a surreal boast that ‘our’ cluster munitions are kinder than ‘theirs’.

The US administration also seems to have made elaborate efforts to minimise dissent both at home and among Ukraine’s European allies. Republican leaders in the US Congress issued a statement saying the move would allow Ukraine ‘to target and eliminate Russian forces more efficiently’, while the German government produced a helpful statement to the effect that, while they would not supply such munitions, they understood the reasons for the US decision and, by the way, Russia had used cluster bombs first. Any objections have come from groups such as Amnesty International and Human Rights Watch or politicians out of power.

Part of the reason for this – perhaps surprising – acquiescence on the part of Europeans surely relates to the timing. Nato members are concerned to present an appearance of cast-iron unity before the summit in Vilnius next week, when continuing support for Ukraine will be central in their deliberations. Any potential dissenters will keep their counsel until that meeting is over.

Another part of the reason, however, might reflect a still more significant concern. Was Biden exaggerating in order to bolster a difficult decision, when he said that Ukraine was ‘running out of ammunition’ or was he admitting an awkward truth? Is Ukraine, a month into what appears to be its faltering counter-offensive, in fact running short of ammunition to this degree and has the US had to step in because the Europeans are also running short of the wherewithal to resupply Ukraine?

Western forecasts early in the war suggested that Russia would be first to run low on weaponry, but it appears to have been able to introduce new production capacity, unlike most of Ukraine’s US and European backers. If cluster munitions are some sort of last resort, then Ukraine is in a double bind. Not only is its war effort in trouble but any use of cluster bombs – even if they can be presented as more discriminating than those used by Russia – cannot but weaken its claim to occupy the moral high ground. In extending this help to its protege, the United States risks tainting it, too.