Vladimir Putin could launch a "tactical" nuclear strike but it would mean the end of Russian civilisation, a historian has warned.
It is estimated that the Russian president has 2,000 tactical nuclear weapons and some have the power to kill 10s of thousands of people with one strike.
Putin's troops have been met with fierce resistance from Ukrainians and have suffered severe casualties on the battlefield - including forces, high-ranking military generals and top-notch equipment.
There are fears Moscow may resort to using nuclear weapons to get closer to achieving its vision of victory following its failed campaign.
Expert in modern history, Dominic Sandbrook, has said one plausible scenario that could spark this is if the Ukrainians launch a counterattack in the Donbass - a region Putin wants to hold on to.
Mr Sandbrook wrote in the Daily Mail : "One plausible scenario is that if the Ukrainians mount a counterattack in the Donbass — and especially if they threaten his grip on Crimea — Mr Putin might authorise a 'tactical' nuclear strike, using short-range weapons devised for use on the battlefield.
"And even somebody as drunk on his own nationalist resentments as Vladimir Putin must realise that a nuclear war would mean the end of Russian civilisation — the end of Moscow, St Petersburg and everything he and his cronies claim to revere."
Launching a tactical nuclear weapon would "cause all horror of Hiroshima" on a "smaller scale", according to the journal Scientific American.
The journal concluded: "It would also cause all the horrors of Hiroshima, albeit on a smaller scale.
"A tactical nuclear weapon would produce a fireball, shock waves, and deadly radiation that would cause long-term health damage in survivors.
"Radioactive fallout would contaminate air, soil, water and the food supply (Ukrainians are already familiar with this kind of outcome because of the disastrous meltdown of the Chornobyl nuclear reactor in 1986).
"No one knows if using a tactical nuclear weapon would trigger a full-scale nuclear war. Nevertheless, the risk of escalation is very real. Those on the receiving end of a nuclear strike are not likely to ask whether it was tactical or strategic. "
It comes as Russian commentators and journalists have called for Putin to use nuclear weapons on state-controlled TV.
Alexander Sladkov, a "propagandist" for the Kremlin, has claimed Vladimir Putin will soon have "no way back" but to unleash nuclear weapons on Ukraine.
Sladkov told his 730,000 followers time may be approaching for the “last resort” because some 40 countries are arming Ukraine with weapons that are being used against the Russians.
And Dmitry Kiselyov, the deputy head of the company behind the state-controlled Rossiya 1 channel, demanded that the British Isles should be flooded twice with Putin’s most advanced nuclear weapons.
