David, I’ve certainly never seen anyone contemplating an invasion of Russia/Ukraine up the east coast of the Black Sea – that would indeed be monumentally stupid. But it would be a relatively simple operation for NATO to reinforce Ukraine by moving troops etc. through Germany and Poland. Mind you, by the time the politicos got their act together it would probably be too late, Putin would have occupied eastern Ukraine and the Odessa area in the south and he would be impossible to dislodge.
Note that Putin isn’t so stupid as to want to gobble up all of Ukraine, trying to take over the heartland from Lviv in the west to Kyiv in the east would give the Russians a massive case of indigestion.
It is ugly geo-politically.