Everywhere the President of the United States goes, they are accompanied by an aide carrying what’s known as the nuclear football. Unlike your regular pigskin, however, this holds the fate of the world within.

Also known as the Presidential Emergency Sachet, the football is actually a black briefcase containing several items that must be used in order to initiate a nuclear strike. Among these is a plastic card called the "biscuit", upon which is printed a series of Gold Codes that the commander-in-chief needs to consult when ordering such an attack - yet these aren’t the same codes that actually cause the missiles to fire.

In the US, the President is the only person with the authority to order the employment of nuclear weapons, but this doesn’t mean they have access to a "nuclear button". Instead, when a chief executive wants to fire a nuke, they first have to convene a conference of leading military and civilian advisers, all of whom are under orders to ensure that the President’s demand is in accordance with international humanitarian law before carrying it out.

As long as no foul is called, the President will then open the dreaded nuclear football. Inside is the so-called "Black Book" containing a menu of different strike options, one of which will be selected and communicated to the Pentagon’s War Room. It’s at this point that the Gold Codes come into play.

To ensure that the order really is coming from the President, a senior War Room officer will issue a “challenge code”, typically consisting of a series of phonetic letters from the military alphabet, such as Papa-Tango. To confirm their identity and authenticate the order, the President must respond using the corresponding Gold Code found on the biscuit.

Now the ball really gets rolling. With the strike authorized, the War Room prepares a launch order, an encoded message that is sent to launch crews on submarines or at land-based centers, depending on which type of nuclear weapon has been selected for the attack. 

This order contains further codes known as sealed-authentication system (SAS) codes, as well as the combinations required to open locked safes at the various launch crew sites. Upon opening these safes, launch crews will find a further set of SAS codes, which must match those in the launch order.

This message also provides details of the chosen war plan and targets to hit. As for the actual codes that unlock the nuclear missiles, these may be contained within the safe or included in the launch order, depending on which types of weapons are being used and where they are being fired from.

However, thanks to the so-called two-person rule, it is impossible for any single officer to fire a nuke on their own. Instead, two weapons operators must verify the codes and simultaneously turn their keys on a control panel before a missile can be unlocked.

Once the missiles are airborne, though, there’s no way of recalling them, which is why so many authentication steps are required in order to carry out a strike. Ultimately, none of this can happen without the President’s go-ahead, but it’s reassuring to know that there’s no single person with their finger on the big red button.

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.