Realpolitik. I don't think starting a nuclear war is a good idea. So understanding why Putin is doing what he's doing is vital to get a positive outcome (as opposed to blowing everyone to bits). Half the posters on here don't seem to realise Russia couldn't possibly sustain a shooting war with the USA so would need to resort to first tactical, then strategic nuclear weapons if backed into a corner. Of which they have over 6000 by the way. More than enough to blow everyone to bits on the planet. And 70 submarines that are somewhere under the oceans just waiting for the command to fire their missiles.
A little caution might be called for. Putin has already implicitly threatened all out nuclear war.
Agree with that post. I withdraw my snarky previous remark.