> I don't think the West ever threatened a nuclear response to Russia's invasion of Ukraine.

I think so, too, but I also think it’s likely that, through silent diplomacy, there was a clear message “if you nuke the Ukraine, there will be a response in kind”.

Without the USA, it’s hard to keep that message, though. Neither England nor France can respond in kind to a tactical nuclear weapon, as they don’t have any.

um: https://en.wikipedia.org/wiki/Air-sol_moyenne_port%C3%A9e