Vladimir Putin has repeatedly talked of using “all possible measures” and other coded references to nuclear weapons in his war with Ukraine. Is this a realistic prospect?
Nuclear weapons fall into two basic categories: tactical and strategic. There is no agreed definition of ‘tactical’ but factors such as size, range and intended use against defined military targets to achieve limited goals of winning single battles are considered factors. This contrasts with strategic weapons which have a broader goal of targeting the enemy’s war-making capability at levels other than just the frontline battlefield – for example, manufacturing, infrastructure and communications. The weapons Putin might use in Ukraine are much more likely to be tactical, or ‘non-strategic’ as they are sometimes termed.
The science of nuclear weapons
Nuclear weapons depend on nuclear fission for their destructiveness (ignoring for now thermonuclear weapons which use fission to start a nuclear fusion process). Fission in turn requires certain isotopes of certain elements. Isotopes are forms of the same element, i.e. they have the same number of protons, but different numbers of neutrons in their nucleus. They are referred to by their atomic weight – for example, 235 and 238 for uranium. Only 235U is fissile, likewise, the fissile isotopes of plutonium are 239Pu and 241Pu.
Nuclear processes depend on chain reactions where neutrons are released due to fission, which impact other atoms releasing further neutrons and causing more fission. In a nuclear reactor, this is a controlled process, in a weapon it isn’t and so a weapon releases its energy far more quickly.
Another requirement for sustained nuclear fission is a minimum amount of material to sustain it – the ‘critical mass’. The earliest nuclear weapons worked by firing two chunks of 235U at each other but subsequent developments produced a design with spherical ‘pits’ of fissile material surrounded by explosive charges. Ordinarily, the density of the fissile pit material is below the critical mass. When the weapon is deployed the charges are detonated and act to compress the pit such that it reaches critical mass and a chain reaction ensues.
The nukes don’t work
Nuclear weapons are fickle mistresses. They require a huge amount of routine maintenance and the US is estimated to spend $60bn annually in the period 2021–2030 to maintain its nuclear arsenal. The explosive charges surrounding the pit need to be triggered in a precise sequence to achieve critical mass and are degraded by continual exposure to the radioactive pit.
Both uranium and plutonium are very susceptible to corrosion and this affects the shape of the mass forming the pit of a nuclear weapon. Yet the shape of the pit is key to achieving criticality and the release of energy sufficient to create a nuclear explosion. For this and other reasons the United States overhauls individual nuclear weapons every ten years.
At the start of the Ukraine invasion, we were treated to the sight of Russian convoys stranded, often on failed tyres which hadn’t been maintained properly. The implication of this was that corruption within Russian ranks had siphoned off funds intended for routine maintenance of these vehicles.
Now, let’s speculate on the actions of those notionally responsible for maintaining Russia’s nuclear arsenal. We know that corruption is rife in Russia and as a lowly weapons technician you might not unreasonably assume that the nukes you are caring for will very probably never be used. The temptation to appropriate nuclear arsenal maintenance funds would be overwhelming and the chances it has happened extremely high.
Given Russia’s desperation in pressing obsolete tanks into service and arming their latest conscripts with rusty weapons, it seems entirely plausible that Russia’s nukes can’t be fired and wouldn’t work even if they could be. This especially applies to thermonuclear weapons, which are precision engineered devices and would require even more maintenance than conventional nuclear weapons and which would be far too destructive to fall into the category of ‘tactical’ nukes.
The limited utility of tactical nukes
Add to this that nuclear weapons just aren’t that effective in field combat: the Ukrainian forces are too thinly spread for a tactical nuke to have a significant effect. Nuclear weapons work by creating an extremely powerful explosion – but in open countryside (which much of Ukraine is) this isn’t particularly effective.
It could have significant local impact, perhaps up to a few miles radius from the blast site depending on the size of the weapon, but the energy of the blast would dissipate too quickly over distance. The Ukrainian front line is at least 500 miles (800 kilometres) long. This is partly why the US nuclear attacks on Japan at the end of World War II targeted cities – the effect of the blast is far greater.
Modern conventional weapons have developed in the last 40 years to the extent that they can achieve the goals of a tactical nuclear strike without the risks of nuclear fallout. The spread and effect of this fallout are very difficult to predict and you have to drive your troops across that fallout zone to capitalise on the battlefield advantage notionally conveyed by a nuclear strike.
Russian military doctrine is to use tactical nuclear weapons to ‘punch holes’ in the Ukrainian lines and then have highly mobile mechanised Russian units advance through these holes to drive deep into the rear areas of the Ukrainian troops. This all requires highly trained, well-equipped and skilled troops – which is exactly the opposite of what we have seen from Russia in the Ukraine war as of late 2022.
Logic would suggest sending your best resources into battle first, to overwhelm the enemy and secure victory as quickly as possible, so it seems unlikely that Russia is holding back such troops for potential later stages of the war. This is especially likely given that Russia intended to win the war in a matter of days.
Even if used to stall Ukrainian military advances, a nuclear strike would at best result in a ‘frozen stasis’ whereby Putin could (temporarily) hold on to captured Ukrainian territory – a far cry from the originally stated war aims of capturing all of Ukraine. The risks from such a strike are extremely high for Putin.
Geopolitical implications of a nuclear strike
Current Russian allies or neutral countries such as Iran, India and China would, politically speaking, be unable to ‘turn a blind eye’ any longer if Russia did deploy a nuclear weapon in Ukraine. China and India were responsible for half of Russia’s oil exports in September 2022 and they would find it difficult to justify continuing to buy Russian energy if Putin used nuclear weapons.
Chinese President Xi said in early November 2022 that, “The international community should… advocate that nuclear weapons must not be used and nuclear wars must not be fought, in order to prevent a nuclear crisis in Eurasia”. Whilst not mentioning Russia by name, the meaning of his words is clear, and Putin will have heard them.
Quite apart from the fact that NATO would also be bound to retaliate, public opinion in non-NATO countries such as Brazil would certainly swing. Brazil is officially neutral to Russia but outgoing president Jair Bolsonaro had been making distinct overtures towards Putin and Putin claims good relations with president-elect Luiz Inácio Lula da Silva. This would be unsustainable if Putin launched nukes and the effect would not be limited to Brazil. Russia’s threats were widely condemned at the UN General Assembly in September 2022.
Although enforced conscription has undermined the ‘special military operation’ excuse for invading Ukraine, Putin still justifies his war on the grounds of NATO aggression, ‘de-Nazifying’ the country as well as ‘liberating’ and returning Ukraine to ‘Mother Russia’. A nuclear attack would utterly shred these political claims, not to mention the question of irradiating the land and razing the cities of a country that Putin claims benign attitudes towards. It would be hard to see how Putin could retain power in such circumstances.
The Armageddon factor
Overall, the threat of nuclear weapons is more powerful to Putin than having his bluff called by trying to actually use them. The threat has dissuaded the US and its allies from taking more interventionist action such as a ‘no fly’ zone over Ukraine. The evidence overwhelmingly suggests Putin is bluffing, but the consequences of the tiny chance of being wrong are too terrible to contemplate. The stalemate and unnecessary bloodshed and suffering that have held sway in recent months are therefore likely to continue.