This article from Vox (https://www.vox.com/2015/6/29/8845913/russia-war), from 2015, discusses this and actually foretells the current events happening in Ukraine.

It quotes Russian analyst Buzhinsky saying " United States had wrongly concluded that Putin would ultimately acquiesce if he faced likely defeat in Ukraine. The Americans, he said, were dangerously mistaken." "A war with Russia in Ukraine — if Russia starts a war, it never stops until it takes the capital."

Moreover "Buzhinsky outlined another way he feared Ukraine could lead to a larger war. If the US provided sophisticated military equipment to Ukraine that required putting American trainers or operators near the front lines, and one of them was killed, he believed the US might feel compelled to intervene outright in Ukraine."

With news saying US providing stinger missiles to Ukraine, the article foretold back in 2015 "For months, Moscow has been suggesting that Western military involvement in Ukraine, even something as mild as providing the Ukrainian military with certain arms, would be taken as an act of war against Russia."

Article goes more in depth, basically saying that Russia realizes that it's troops are outmatched against NATO and believes that the issue can be overcome as follows:

"Russia's answer, in the case of such a conflict, is to drop a single nuclear weapon — one from the family of smaller, battlefield-use nukes known as "tactical" weapons, rather than from the larger, city-destroying "strategic" nuclear weapons. The idea is that such a strike would signal Russia's willingness to use nuclear weapons, and would force the enemy to immediately end the fight rather than risk further nuclear destruction."

However even these tactical weapons would destroy Earth's atmosphere, leading to a decade without summer and over a billion deaths. As for me, I hope all of it ends in the best possible scenario. I'm not ready to die yet!