It's about being able to take out the other guy's nuclear and conventional forces, population centers, industrial capacity and command and control, even after accounting for both strikes on your own nuclear weapons and interceptions.I would like to go on a small tangent here: Russia's nuclear stockpile and its size doesn't matter at all. It is the most impotent claim in the pro-Russian arsenal.
They can blow up the world 1000 times over. We can only do it 950 times!
Morons. It doesn't matter after the first time.
It does matter, it's not purely academic and it has real world consequences. The super powers didn't do it because it seemed like a fun way to spend money.