Russia in Ukraine showing a dynamic we didn’t really see in the Cold War, which is that as long as you aren’t existentially threatening a nuclear rival’s core, you can actually deplete your home conventional forces pretty far without fear of a counteralliance with superior conventional force exploiting your weakness at home if they’re backstopped with a nuclear threat.

(In the Cold War the US needed to maintain force strong enough to defend Western Europe, and a lot of geopolitical maneuvering was about if the rubber hit the road what if any of that counted as part of our “core”, and what if any leverage it had to act in its own right)