[cess11]

I don't think there are any "nuclear codes". I think they might have been a thing at some point in history since the idea is so pervasive, but in a crisis you'd not want someone to have to figure out some non-trivial password before MAD doctrine can be applied.

Maybe I'm wrong, I know more about field tactics and guerilla warfare than grand strategy.

[Yoric]

I remember reading somewhere (atlas obscura, maybe?) that the US military was much more scared of a rogue general launching a nuclear strike than of the USSR starting the war.

So I'm going to assume that there is _some_ kind of code.

[pjc50]

Apparently at one point they were set to "0000000".

[magicalhippo]

Reference: https://sgs.princeton.edu/00000000