A historian believes it is possible Russia will use chemical weapons as the country has used them before and "showed no compunction" about doing it.
Professor Margaret MacMillan, a historian at research institute LSE IDEAS, said: "It will be very difficult for him (Putin) to back down now", partly due to his big goals but he faces "humiliation" due to the underperformance of his armed forces.
She referenced that captured Russians had dress uniforms in their luggage – proving that Putin thought the conflict would be very short.
Prof MacMillan said: "I think they really believed, and Putin seems to believe, that it will be a victorious march through an acquiescent Ukraine, the whole thing will be over in two days.
"Now we're getting close to four weeks and the Russian army has taken, and is continuing to take, really dreadful losses, as are the other forces, the navy, and the air force, as well."
The historian believes whether Russia uses nuclear weapons or not "remains an open question".
Concern should be raised, she says, in relation to Putin's tactics which have involved him accusing enemies of doing what he is just about to do.
"So, he's accusing Ukraine of making chemical weapons," the professor said. "He's accusing them of wanting to get nuclear weapons which, of course, they gave up in the mid-1990s, and so, you know, it's an absurd accusation.
"He often accuses those he's about to do something awful to of what he is himself going to do," she added.
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(Article cover image: Nadia Isakova/Alamy Stock Photo).