On the morning of Inauguration Day, which usually takes place in January after November elections, the new US president takes part in a sobering ritual giving him the power to launch thousands of nuclear missiles.

After taking the oath of office, either Donald Trump or Joe Biden will receive the nuclear launch codes in a highly-sensitive ceremony that takes place out of the public's eye.

Speaking of the ceremony following his election in 2016, Trump, 74 said: "When they explained what it represents and the kind of destruction that your talking about, it's a very sobering moment, yes. It's very, very... a very scary thing in a sense."

Asked if having an aide carry the launch codes with him wherever he was on the move kept him up at night, he added: "No, but it's confidence that I will do the right thing and the right job, but it's a very scary thing."

A military aid carries the nuclear codes at the White House in 2017

The transfer of the nuclear launch codes allows the US president to set off some 2,000 missiles with the potential of killing hundreds of millions in a matter of minutes.

A 45-pound black satchel, known as the "nuclear football," will always be with the new president wherever he goes, carried by a military aide who trails the president in case the nightmare scenario takes place.

There are no checks and balances in this system.

And if the president orders it, even if congress and his cabinet are opposed, the order is carried out.

The nuclear football is also known as the atomic football, the president's emergency satchel, the Presidential Emergency Satchel the button, the black box, or just the football.

Republican Donald Trump described the ceremony as "very sobering"
Democrat challenger Joe Biden has been leading in the polls

Its contents allow the Leader of the Free World to authorise a nuclear attack while away from fixed command centres, such as the White House Situation Room.

It dates back to Dwight D. Eisenhower, but its current usage came about in the aftermath of the Cuban Missile Crisis, when John F. Kennedy was concerned that a Soviet commander in Cuba might launch missiles without authorisation from Moscow.

In his 1980 book Breaking Cover, the former director of the White House Military Office Bill Gulley, wrote: "There are four things in the Football.

"The Black Book containing the retaliatory options, a book listing classified site locations, a manila folder with eight or ten pages stapled together giving a description of procedures for the Emergency Broadcast System, and a three-by-five-inch card with authentication codes.

"The Black Book was about 9 by 12 inches and had 75 loose-leaf pages printed in black and red. The book with classified site locations was about the same size as the Black Book, and was black. It contained information on sites around the country where the president could be taken in an emergency."

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