With Vladimir Putin facing further humiliation on the battlefield in Ukraine, there are increasing fears his army may use a “dirty bomb” and blame it on Kyiv.
On Monday, General Valery Gerasimov, the head of the Russian armed forces, claimed that Ukraine was on the brink of deploying such a weapon in a call with his British counterpart, Admiral Sir Tony Radakin.
Russia’s forces were also said to be ready to work in “radioactive conditions” at a briefing on the issue by Lieutenant-General Igor Kirillov, the head of the Radiation, Chemical and Biological Defence Forces of the Russian Armed Forces.
The rising drumbeat of propaganda follows calls from General Sergei Shoigu, Russia’s defence minister, to his counterparts in Britain, France, Turkey and the US on Sunday claiming a “dirty bomb” strike was coming soon.
All the Western governments have roundly rejected Russia’s claims and warned the world will see through any attempt to blame a dirty bomb attack on Kyiv.
But what is a dirty bomb, and what effect would it have on the war if one were used?
First, it is important to understand what dirty bombs are not.
Dirty bombs are not small nuclear devices and cannot kill and injure as many people as a nuclear weapon would.
Instead, they are primarily tools of terror, in that the psychological impact of any potential use far outweighs the actual effect of the weapon.
Designed to scatter radioactive material that has been placed around a conventional explosive such as dynamite, the blast from a dirty bomb is only as powerful as the underlying munition.
An atomic bomb’s explosive power comes from a nuclear chain reaction acting on plutonium or uranium that has been concentrated and highly enriched to about 90-95 per cent purity.
Nuclear power plants, in contrast, use radioactive isotopes (again, mainly uranium or plutonium) that have been enriched to about a fifth of this figure. The subsequent chain reaction produces heat that can be converted into electricity.
The radioactive material in a dirty bomb does not have to be the extremely pure uranium or plutonium found in atomic weapons but could come from any of the many radioactive sources used in medicine and industry.
In a dirty bomb explosion the contaminated material will generally go only as far as the explosion will allow it. Fine particles may travel on the wind, but to have a significant impact a huge amount of radioactive material would be needed.
Anyone who survived the initial explosion could ingest some radioactive material and need medical treatment. However, few would take in enough to produce radiation sickness.
Depending on the amount of radioactivity present, the area of the blast would have to be decontaminated, abandoned or possibly even demolished.
Even once sufficiently decontaminated, people could choose to stay away from the area for fear of the long-term health impact.
If a small number of devices laced with radioactive material were to explode in the financial district of a city, regular work could be disrupted for a significant period of time and may never recover fully, with serious implications for the economy.
On April 7, 2018, Syrian forces backed by the Russian army carried out a false flag dirty bomb attack when chemical weapons were used in the city of Douma.
Around 50 people were killed, with hundreds wounded, in the atrocity which came days after Moscow "warned" of a likely attack of that nature by forces opposed to Syrian leader Bashar al-Assad.
Russia may now choose to deploy a dirty bomb in Ukriane in the hope that such a device, confusingly placed somewhere between conventional and nuclear weapons, will puzzle and divide any response.
Putin needs to shift attention from the battlefield and regain the initiative in the war. He may calculate a dirty bomb blamed on Kyiv will be the excuse he needs to retaliate with a ferocity that will please his internal critics and intimidate Ukraine's western backers.