In shock like most of us, I am trying to play out the various options for Ukraine and the west. None are good. What others can you suggest?
Ukraine quickly surrenders, Putin installs puppet government. Much repression, modest insurrection, if that, as in Crimea.
West wimps out: Russia walks away with success, looks for next target. Extreme sanctions: Russia toughs it out, or Russia capitulates, restoring a battered Ukraine. Or Russia goes nuclear.