//BUT I fear that the lunatic Putin would push the button rather than accept defeat.//
That is entirely possible, but the alternative is to raise the white flag and hand over the entire West to Putin. No doubt many of us would be tracked down and murdered anyway so we have to make a stand. The Ukrainians have shown us how. Putins forces dont seem to be as powerful as he makes out, the Ukrainians, whilst I fear they will ultimately loose, have really held them to account despite being massively outnumbered and out armed.
It is of course possible that if it goes further the Russian people will rise up as they will be more than aware if he pushes his button Russia will be wiped off the map, with them taken too.