What scares me is that, although Hitler and Czechoslovakia is used to explain Crimea, when Hitler made his move, the world didn't have nuclear weapons. Mutually Assured Destruction worked during the Cold War, when the threat was USSR against the West, but this is a new scenario. We are unlikely to use conventional force against Russia (could we?), to defend sections of a country, and our only other option is nuclear. So, Putin "liberates" countries a bit at a time. What then?