Right. And also you can never take that threat seriously when Russia is using it while on the offensive, because following that logic you should let them do whatever they want because nukes.
>We are not going to blow up the world to save Ukraine and Russia/Putin knows this. If he decides to use nukes what are we going to do? What can we do?
They are not going to risk their security for Ukraine. They wouldn't risk starting a nuclear war over Ukraine, it's stupid, even for their standards
If anyone use any nuke, the world as we know it is done, Ukraine might not be able to retaliate but others have already promised to. France did for instance.
No one want it, Putin and especially China. Current atomic weapon are no more the little Nagasaki Firecrackers.