They are obvious insincere, because they've been idly making them about every minor gesture the West has made in Ukraine's favour. And ultimately it is strategically impossible for there to be any good outcomes of a nuclear attack on Ukraine for Russia, never mind "better than conventional war Russia have marginal advantages in" or even "better than retreat to pre-2014 borders".
If they were obviously insincere, they could just be ignored. But we can see that in practice, US/Europe have been hesitant to escalate too much or get directly involved with troops. Which is part of the reason for making those threats over and over. While each one is most likely posturing, they cannot be blanket ignored, because Putin has an advantage in an escalation scenario. Making those threats is a way of repeatedly emphasizing that fact.
And of course there can be an advantage for Russia in using nukes. They could destroy Ukraine's entire army, kill all its leaders, destroy all its infrastructure, etc. with no risk of (nuclear) retaliation. There would be many negative consequences too, so it's not likely to happen unless the conventional war is going very badly for Russia, but it's certainly a card they hold.
The idea that there would be no nuclear retaliation the moment Russia launches any known nukes is ridiculous. If they actually launch a nuke, any non instantaneous retaliation will be too late.
The reason the EU countries don’t just waltz into Ukraine probably has more to do with the knowledge they’re not dealing with a rational person, but with a bunch of ego. It’s not hard to predict how Putin will respond if his ego is threatened, but how the rest of Russia will respond to the command to launch nukes.
It’s not unlike the US, except it’s currently still fairly easy to predict that any US commander will just say no when ordered to fire on the EU.
If Russia nuked the Ukraine, I would be astonished if the West didn't invade Russia. The primary goal being the end of Putin, and all those who aided him. If resisted, and Russia threatened more nuking, then Russia would need to be nuked.
(I expect a first response would be a single city, with warnings to evacuate.
A show of what's next.)
The goal would be that Russians assist in taking out an out of control, lunatic who will destroy us all.
Understand, this isn't just about today. Over the next 100 years, every country will obtain the capacity for nukes. Every person on this planet needs to see, and know that using them indiscriminately means you lose.
I’m more inclined to think it’d be a direct beeline for moscow with a swarm of jets (kinda like what Russia tried, only successful). Nobody in Russia has any appetite for this war and they’ll take an out when it’s given to them.
At that point, as I stipulated "The West", multiple countries would be boots on ground, invading Russia. If Russia gave an ultimatum to nuke at that point, and was serious, it would make perfect sense to nuke a city of theirs first.
This isn't a game you win by backing off. There is no safety in that move.
Understand, the claim that the Ukraine is "Russian" is an absurd bluff. No one truly believes that, not Putin certainly. There are a dozen other countries in that region that Putin could make the same bluff about.
By allowing this bluff to continue for this long, matters have only gotten worse. We allowed 2014 to happen. Now, we're here. It won't stop a a peace agreement, or at Ukraine in whole.
The insanity is Russian. And you don't leave a rambling, insane man with a gun outside your house, shooting randomly at houses, because they're not quite at your doorstep yet.
