I'm going to take another stab, this time at Russia's ability to pull this off. First, let me say up front that I do not believe for a second that it's a forgone conclusion that Russia will lose this battle.  Mass is its own thing and Russia has it and Ukraine does not.  Russia also is (apparently) going to do what it does best which is to throw all that mass into the fight nearly simultaneously from many directions all at one time.  It will be difficult for Ukraine to resist it everywhere