There has been a lot of talk about the fact that after his inauguration, Donald Trump will have his finger on the “button” used to launch nuclear weapons. But the president does not actually have a “button.”
Instead when he becomes president he will be given nuclear codes that enable him to launch a nuclear strike.
What does that actually mean?
The Nuclear Football: Speed Matters
The US nuclear launch system is built for speed: it is designed to allow the president to be notified of warning of an incoming attack, be briefed on the specifics, decide what to do, and launch the response, all in less than the 30 minute flight time of an attacking long-range missile.
This demanding timeline was established during the Cold War to allow US land-based missiles to be launched on warning of an attack, before the attacking missiles could land and destroy them in their silos. It persists today despite the fact that most US nuclear weapons are deployed on submarines at sea, which are invulnerable to such an attack; quick launch of land-based missiles is therefore no longer needed for deterrence.
The short timeline means in practice the president may have less than a minute to be briefed by military officers and his advisors, and have fewer than 10 minutes to decide whether to order a launch.
Warning of attack could come when the president is essentially anywhere, with no time to get to the White House situation room or the Pentagon.
The only way to make this system work is to ensure everything the president needs to order a launch is never far from his side. So he is constantly escorted by a military officer carrying a 45-pound “nuclear briefcase”—typically called the “football.” The football contains, among other things, the “black book” that lists the menu of preset launch options the Pentagon has drawn up.
The Nuclear Codes: Who’s Who
The president could also, in principle, use the football to order a nuclear strike that was not in response to an attack.
No matter why he ordered a launch, the president needs a way to convince those in the military who actually carry out the launch order that he really is the president and not, for example, a Russian hacker.
That’s where the “nuclear codes” come in. They aren’t codes to actually launch missiles, but to allow the president to prove he is authorized to order a launch.
The codes are a list of letters on essentially a 3×5 card, called the “biscuit,” which are updated daily. To prove he is the president, he must be able to provide the right code from the list on the card. The card may be carried in the football, although some presidents have chosen to carry it with them.
Once the president has provided the proper codes for the day, no one has the authority to stop the launch process.
The Nuclear Launch Order
Once the president has provided the correct identification codes and his launch option over a secure communication line, officers in the Pentagon’s “war room,” or National Military Command Center (NMCC), send out encrypted messages, called the Emergency Action Messages (EAMs).
The EAMs are the actual launch orders giving the details of the launch. The EAMs would go, for example, to the officers in the various underground Launch Control Centers who would launch US land-based missiles.
The EAMs specify the launch plan, including the targets and number of warheads to be launched, and the time of the launch. They also contain launch authorization codes that allow the launch crews to confirm that the order is real by comparing it to codes they have in their safes. These are called “sealed-authentication system” (SAS) codes.
Once the EAM arrives, ICBM crews can launch their missiles in 60 seconds and submarine crews can launch in 12 minutes. In that time, the US could launch some or all of the roughly 900 nuclear weapons it keeps ready for immediate launch. The remaining deployed weapons in the US arsenal would take longer to launch. These include aircraft carrying bombs and cruise missiles, and missiles on submarines at sea but out of range of their targets.
For a discussion of presidential authority to launch, see here.