Nuclear War (and this time I really really mean it.)
Putin appears to be desperate. At the rate their victories are happening the Ukrainians will be in Sevastopol in no time. His decision to call up reservists is very unpopular in Russia. Mothers don’t want to send their sons off to die. 300,000 out of shape, barely trained and totally unmotivated troops won’t turn the tide. That’s even if they can be outfitted with anything better than Mosin Nagants.
He’s doubling down by the shame votes to incorporate the conquered territories into Russia. That way an attack on them will be an attack on Russia itself. The West isn’t buying it. Not only that, why should Ukraine limit themselves to fighting on their own territory? There are transportation and communication hubs in Russia proper that are perfectly valid military targets.
Russia doesn’t have what it needs to win this war. What it does have is nuclear weapons. The problem is that they are not the weapon for the job. Even tactical nukes don’t make much military sense. Ukrainians are very good at dispersing their troops and only bringing them together when needed for an assault. When that happens they are too close to Russian troops to safely use nukes.
Use of strategic nukes is a suicide pill. Maybe Putin is suicidal, but I doubt the rest of the Russian government is. I don’t expect this conflict to go nuclear. If the major European capitals go up in radioactive flames I’ll be terribly embarrassed.