Who controls the nuclear weapons in the US?

Answer 1

The President must authorize any use of them.

This is one of those questions, which, on surface seems deceptively simple, but the reality is much more complex.

In the US, there are three concepts related to the actual use of nuclear weapons:

1. Physical custody of the weapon
2. Control of the weapon's use
3. Launch (use) authorization

The last case is what people typically think of as "controls", but read on, as reality is much less simple.

To use a nuclear weapon, here are the following steps:

1. The President must decide that nuclear weapon use is appropriate
2. The Secretary of Defense must concur in this decision (i.e must agree that circumstances warrant the use of such weapons)
3. The President's AUTHORIZATION codes (along with the SecDef's confirmation) are sent to the military commander in charge of the unit(s) deploying the weapon system(s) chosen to be used.
4. If the war plan that the President chose determines that weapon use should happen either immediately or at a specific time, the military commander then transmits the AUTHORIZATION codes, plus that commander's AUTHENTICATION codes, plus the Targeting information to the holder of the actual weapon (the people who have "physical custody" of the weapon - the missile launch controllers, the submarine commander & executive officer, the bomber pilot & co-pilot, etc.)
5. The weapon operators check the Authentication codes against a known codebook. If they pass, then then open special safes (using a key or combination unique to each of the pair of operators) which hold other codebooks. They then check the Authorization codes with the codes for the specific plan to be executed. If they match, they then enter the Targeting information into the weapon system, and BOTH of them must then simultaneously initiate the launch.
6. If, at #4, the plan the President chooses delegates the launch Authorization to a commander (say, the President authorizes a general to use the weapons if the proper circumstances come up), then the commander in #4 can issue a launch order at their discretion (or, not do it at all).

Theoretically (and, possibly, with some non-trivial effort and help), it would be possible for a rogue military commander (#4) to FAKE the President's Authorization codes, and then give false launch orders to the weapon system owners, and those owners would not be able to tell the fake Authorization from the real Authorization. They would see a perfectly legal launch order.

In addition, there is the possibility of the weapon system owners deciding to launch on their own authority. This is highly unlikely, since most weapons now require an "arming" code to be input into the weapon before it will detonate - that arming code comes along with the Authentication code from their military superior, and does NOT exist at the weapon site itself.

So summarize: the President (and SecDef) control the POLITICAL decision to use nukes, the military commander controls the OPERATIONAL decision about the use of those nukes, and the weapon system operators control the DEPLOYMENT of the actual weapon.