"I have this awful vision of the Baltic States being seized, NATO unable to respond, Putin then blackmails using nuclear weapons what is called chillingly 'nuclear de-escalation' and NATO is unable to do anything about it.  The alliance collapses and at a stroke, Putin has destroyed … the organization perhaps he fears the most, NATO. America is decoupled from Europe and the world is changed irrevocably.  

Add the other chilling aspect of this, that nuclear weapons are hardwired into Russian defense thinking, then it gets really serious and potentially existential.  Because if there is any hint of a Russian military foot stepping across those borders of Latvia, Estonia or Lithuania that means war under article five of the NATO treaty … but it also means nuclear war in Europe.  

We should never assume rationality in strategic affairs, the human dimension is critical here and history is full of examples of irrational decisions being taken by leaders who believe they can get away with it.  What we've seen [in Putin] is an adventurer, an opportunist who's able to make decisions very quickly to seize opportunities as they're presented."

General Sir Richard Shirreff (Ret.), who served as NATO's Deputy Supreme Allied Commander, speaking with London Reporters May 18, 2016.  He referred to the Russian annexation of Crimea as a "copybook military play."