They aren't bluffing.
That's the problem.
This is why Putin moved serious naval hardware into the Med.
After 12+ years of war we are in no position right now to fight Russia unless nukes come into the picture. If that happens we all know where it will lead thanks to the Cold War hysteria.
"And I heard a voice in the midst of the four beasts and I looked and behold a pale horse, and his name that said on him was Death... and hell followed with him."