Russia is peddling implausible tales of Ukrainian ‘dirty bombs’. Kyiv and the West are embarked on a campaign to counter this propaganda, and again the talk is of the risk of Moscow using weapons of mass destruction in Ukraine. And that’s the point.

First of all, Russian Defence Minister Sergei Shoigu broke months of relative silence – with the West, at least – and called his British, American, French and Turkish counterparts. His main message was to assert, with no evidence in support of his claims, that Kyiv was preparing to use a dirty bomb. This is a conventional munition, around which is packed radioactive materials, which is dispersed when it explodes. Such a blast would be much less destructive than almost any nuclear explosion, but would still be considered a proscribed weapon of mass destruction.

Shoigu’s western interlocutors were quick to dismiss the allegations, and to warn that they cannot be used as a pretext for Russian escalation. Nonetheless, the Russians have continued to double down, saying that Kyiv plans to detonate a dirty bomb on its own soil as a false flag provocation, claiming that it was a Russian low-yield (non-strategic or ‘tactical’) nuclear attack. Now, it is bringing its assertions to the UN Security Council.

A dirty bomb is a terrifying concept, but a poor weapon of war. The fallout would contaminate the immediate vicinity, but people would be unlikely to suffer fatal or even seriously harmful dosages of radiation. Furthermore, there could be no question of it being mistaken for an actual nuclear explosion as the blast and radiation profiles would be entirely different.

In any case, Kyiv is moving quickly to address the claims. At its request, the International Atomic Energy Agency has announced that it will dispatch inspectors to the two Ukrainian nuclear sites mentioned by Russian sources, the Eastern Mineral Enrichment Plant in Dnipropetrovsk region and the Institute for Nuclear Research in Kyiv. Nuclear materials are carefully inventoried and tracked, and there can be no question of substantial quantities being diverted without trace to build some putative bomb.

So what is Moscow playing at? The inevitable fear is that they are setting the scene for their own use of such a weapon, which they will blame on Kyiv. However, this would be ‘an act of nuclear terrorism,’ to quote the Russian Ambassador to the UN Vassily Nebenzia. It is also hard to see what real value this would have. A dirty bomb could perhaps have some limited effect on the battlefield, making access routes towards Kherson or Crimea harder for the Ukrainians to traverse, but this would be a small and temporary advantage.

Likewise, although it could be used as an excuse for some other escalation, Moscow has not needed any real excuses in the past. Besides, the Kremlin has a track record of making such spurious claims and nothing coming of it. In March, it claimed there was a joint US-Ukrainian biological warfare programme, quickly debunked by the UN. In April, it was the turn of a dirty bomb, and then in June, that Kyiv was preparing a false flag chemical weapons attack in Odesa, which in July shifted seamlessly to Donetsk and Mykolaiv. None of them, needless to say, ever materialised.

It may be that the Russians are preparing the ground for something else, such as blowing up the Kakhovskaya Dam to shield the withdrawal of its forces from Kherson. More likely, though, this is just another stage in Moscow’s attempts to undermine the West’s continued support of Ukraine.

It follows, after all, Vladimir Putin’s repeated hints that he might resort to non-strategic nuclear weapons – however unlikely this would really be. There are already voices in the West arguing that some kind of concessions are necessary to avoid an apocalyptic escalation, most recently a letter from 30 members of the US Congressional Progressive Caucus urging President Biden to make a ‘proactive diplomatic push’ to end the war. Although swiftly walked back, it represented the most significant example of division over the war yet in the Democratic party, and very much reflected a fear of such escalation.

Putin seems to have realised that his only real hope of victory is to be found in holding the line long enough for the West to lose unity and commitment to the war. To this end, anything that reinforces the message that he is sufficiently unhinged to escalate the war in disastrous new ways perversely helps his case. Assuming nothing comes of this latest story, we can expect a continuing stream of lurid claims and strikingly little supporting evidence.

Yet there is one tatter of silver lining. Shoigu’s conversation with his British counterpart Ben Wallace may have been just for propaganda’s sake, but it was apparently ‘professional and respectful.’ It also led to a follow-up conversation between Chief of the Defence Staff, Admiral Sir Tony Radakin, and his Russian counterpart, General Valery Gerasimov. Even if these conversations saw no meeting of minds, in times of crisis, it is important to keep open such lines of communication.