THE Zaporizhzhia nuclear plant in south-eastern Ukraine is the largest in Europe. It is being shelled almost by the day as Ukrainian and Russian soldiers contest the strategically important power station on the Dnieper river. The situation is almost unimaginably dangerous, not least because, right now, it is in the interest of neither side to make the installation safe.

Ukraine, of course, has the distinction of being the site of the world's worst nuclear disaster: at Chernobyl in 1986. The fallout spread across Europe, contaminating sheep as far away as Cumbria. Chernobyl isotopes are still being identified in Loch Ness. The risk of history repeating itself grows by the day as Ukraine gears up to drive the Russians back across the Dnieper.

The head of the International Atomic Energy Agency, Rafael Mariano Grossi, says the situation at Zaporizhzhia, which was already damaged when the Russians seized it earlier in the war, is now “completely out of control”. He has been calling for a military exclusion zone around the plant. Pro-Russian correspondents in the West claim that President Zelenskyy is deliberately endangering it in order to focus Western attention back on a war which has slipped from the headlines as energy prices soar.

That is unjustified victim-blaming. It was Russia's illegal invasion which caused this crisis, not the Ukrainian defence forces. Nevertheless, it is highly likely that, by accident or design, this bitter, six months-long conflict could .turn nuclear – and not just from damaged nuclear power stations.

Read more: Ukraine is the sum of all fears as Putin risks all-out nuclear war

Next month, the Kremlin is expected to formally announce the annexation of those parts of the Donbas that it occupies, just as it annexed Crimea in 2014. The move is expected to be justified by a plebiscite in the region, which has a substantial Russian-speaking population. President Putin insists that Ukraine is part of “historic” Russia and should never have been allowed to become independent after the collapse of the Soviet Union in 1990.

This means only one thing, according to military analysts like General Sir Richard Barrons, a former UK Chief of Staff: that Russia will now consider use of nuclear weapons in Donbas as legitimate in the defence of the motherland.

You may think that Putin hardly needs any excuse to use his battlefield nuclear weapons, which are already a key part of the Russian military arsenal. These small-scale nuclear weapons, delivered by artillery or missiles, are designed to “take out” an area the size of a football stadium rather than an entire city. At least, that's the theory.

Clearly the fallout from any nuclear detonation would spread far beyond said sports ground. But contamination from a single device would be unlikely to spread beyond the borders of Ukraine. Moreover, since Ukraine is not in Nato, there would be no immediate question of retaliation in kind under Article 5, which obliges members of the alliance to treat aggression against one as aggression against all.

Russia would claim that nuclear retaliation is justified in halting military “aggression" that threatens the existence of the Russian state. This is pure sophistry of course, but Putin would insist that the annexed territories of Luhansk and Donetsk in Eastern Ukraine ARE part of Russia.

To pre-empt annexation, the Ukrainian armed forces are mounting a counter strike in the Kherson region. The objective is to force Russia back east over the Dnieper River. This would hopefully prevent Russia extending its occupied territory to Odesa and thus cutting Ukraine off from the Black Sea. But more importantly a successful counter-attack would demonstrate to the Western powers supporting President Zelenskyy that the stalemate could be broken, and the Ukraine army could eventually win.

It's no secret that many European politicians would like this war to be ended sooner rather than later. They hope for a Ukrainian victory, of course, but many privately believe President Zelenskyy will eventually have to accept partition. Crimea has already gone. It will take huge military effort to drive the Russians fully out of the Donbas, not least because they have support from the many Russian speakers in the east of Ukraine.

To mount a full-scale counter-offensive, Ukraine would need supremacy of around five to one, according to experts like Barrons and Lawrence Freedman, author of the forthcoming book, Command – The Politics of Military Operations from Korea to Ukraine. With around 100,000 Russian soldiers deployed, that would mean a Ukrainian army of half a million – probably more. Each Ukrainian soldier would have to be trained, armed, fed, uniformed and supplied with ammunition. This on top of the £5 billion a month that Ukraine already requires just to keep functioning.

A successful liberation of the Donbas would require artillery, tanks, air support, radar and field hospitals as well as sophisticated weapons systems like the American HiMARS rocket launchers that have proven so effective in destroying the bridges of the Dnieper over which the Russian Army around Kherson is supplied. The big question this winter is whether recession-hit Europe is prepared to pay the cost.

Read more: Ukraine's heroes are fighting for European civilisation itself, so pass the ammunition

Sweeping Russia out of Ukraine may not require the active involvement of western soldiers, but it will require arms and money. The weapons inventory of countries like Britain is already being rapidly depleted. To restock and build the Ukrainian army may require not military mobilisation, but a degree of industrial mobilisation if Europe is serious about driving Putin out of Ukraine altogether.

Sceptics like the military historian Max Hastings, and the MIT Professor Barry Posen, have long said that this is not possible or even desirable. Hastings was highly critical of Boris Johnson's boosterism over Ukraine and argued that President Zelenskyy would have to accept partition – if only because the West will not go the distance. Humanitarian arguments for a ceasefire will grow over winter. Germany is already reining back its military supplies, according to Ukrainian sources.

Of course, it isn't over till it's over. Russia is suffering terrible casualties. According to Lawrence Freedman, the Russian army cannot continue to suffer like this indefinitely and Putin himself is not entirely secure from his oligarchs. Which is why some analysts are speculating about a nuclear demarche.

As if we didn't have trouble enough, Europe could be facing a nuclear winter.

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