[Goose]

If one of the two negative scenarios I presented as possibilities plays out, we may see a guerilla war in Ukraine. My guess is that it will end quickly and very, very violently. Putin is quite capable of genocide. Will we and other western nations stand by and watch?

Europe, probably yes, they've proven they don't care and that they're willing to elect nationalists to look the other way.  
The U.S., ask me in 4 months and I'll give you a better answer.

Deal! I just hope we don't ever need to answer it "for real" :-).

[Goose]

If one of the two negative scenarios I presented as possibilities plays out, we may see a guerilla war in Ukraine. My guess is that it will end quickly and very, very violently. Putin is quite capable of genocide. Will we and other western nations stand by and watch?

Europe, probably yes, they've proven they don't care and that they're willing to elect nationalists to look the other way.  
The U.S., ask me in 4 months and I'll give you a better answer.

Deal! I just hope we don't ever need to answer it "for real" :-).