First, I found perhaps the
only piece of military doctrine that actually explained, in a clear and concise fashion, how a nuclear order would be carried out. And it’s not some ancient Cold War archival document… it’s from 2015! On the website of the USAF’s (appropriately named) Curtis E. LeMay Center for Doctrine Development and Education, one can find
ANNEX 3-72 NUCLEAR OPERATIONS, last updated in May 2015. It states, in a clarity that (after reading a
lot of DOD doctrine) makes me want to weep with joy, despite the message:
The President may direct the use of nuclear weapons through an execute order via the Chairman of the Joint Chiefs of Staff to the combatant commanders and, ultimately, to the forces in the field exercising direct control of the weapons.
Which seems pretty definitive. The order jumps immediately from the President to the military, in the form of the Chairman of the Joint Chiefs of Staff, and from there percolates through the system of command, control, and communication to the various people who actually turn the keys and put the “birds” into the air.
Could the doctrine be wrong? Presumably such things are carefully screened before being offered up as official doctrine, and it seems about as clear as can be, but it's always possible that something got mangled.
But one other useful piece of evidence is that we asked Perry, the former Secretary of Defense, at point blank whether the Secretary of Defense was in the chain of command. The answer was a clear “no.” Perry explained that while, presumably the Secretary of Defense would express opinions and given counsel, the President was under no legal obligation to take such counsel, and the objection of the Secretary of Defense had no bearing either legally or practically.
I don’t know what your standard of evidence about such a question might be, but personally I find the testimony of a former Secretary of Defense, combined with a reasonably up-to-date piece of Air Force doctrine, to settle the case for me (at least, pending more evidence). No other assertions about the nuclear chain of command that I’ve seen have quite that kind of weight behind them.
.......
.......
Now, obviously conditions would dictate varying responses. I have faith that an “obviously bonkers” order would be somehow avoided (e.g., a frothing, “nuke them all, ha ha ha,” sort of thing). I’m not worried about that situation (it’s not outside the realm of human possibility — all humans are fallible, many develop various forms of mental illness, etc.), but I am worried about what I consider to be “ill-advised” orders, or “bad idea” orders, or “spur of the moment” orders that are considerably less apocalyptic (at least on their surface) than, say, a full nuclear exchange.