The ‘nuclear button’ explained: For starters, there’s no button

HONG KONG — President Donald Trump and Kim Jong Un, the leader of North Korea, traded threats this week about the size, location and potency of their "nuclear buttons."

The image of a leader with a finger on a button — a trigger capable of launching a world-ending strike — has for decades symbolized the speed with which a nuclear weapon could be launched, and the unchecked power of the person doing the pushing.

There is only one problem: There is no button.

[North Korea leader says he has 'nuclear button' but won't use unless threatened]

— What's the deal with the button?

William Safire, the former New York Times columnist and presidential speechwriter, tracked the origin of the phrase "finger on the button" to panic buttons found in World War II-era bombers. A pilot could ring a bell to signal that other crew members should jump from the plane because it had been damaged extensively. But the buttons were often triggered prematurely or unnecessarily by jittery pilots.

The expression is commonly used to mean "ready to launch an atomic war," but the writer added in "Safire's Political Dictionary" that it is also a "scare phrase used in attacking candidates" during presidential elections.

President Lyndon B. Johnson told Barry M. Goldwater, his Republican opponent in 1964, that a leader must "do anything that is honorable to avoid pulling that trigger, mashing that button that will blow up the world."

Richard M. Nixon told advisers during the Vietnam War that he wanted the North Vietnamese to believe he was an unpredictable "madman" who could not be restrained "when he's angry, and he has his hand on the nuclear button."

During the 2016 presidential election, Hillary Clinton said of her opponent, "Trump shouldn't have his finger on the button, or his hands on our economy."

— How would Trump launch an attack?

Each nuclear-capable country has its own system for launching a strike, but most rely on the head of government first confirming his or her identity and then authorizing an attack.

Despite Trump's tweet that he has a "much bigger & more powerful" button that Kim, the fact is, there is no button.

There is, however, a football. Except the football is actually a briefcase.

[Trump veers away from 70 years of U.S. foreign policy]

The 45-pound briefcase, known as the nuclear football, accompanies the president wherever he goes. It is carried at all times by one of five military aides, representing each branch of the U.S. armed forces.

Inside the case is an instructional guide to carrying out a strike, including a list of locations that can be targeted by the 900 nuclear weapons that make up the U.S. arsenal. The case also includes a radio transceiver and code authenticators.

To authorize the attack, the president must first verify his identity by providing a code he is supposed to carry on him at all times. The code, often described as a card, is nicknamed "the biscuit."

In his 2010 autobiography, Gen. Henry H. Shelton, chairman of the Joint Chiefs of Staff during the final years of Bill Clinton's presidency, wrote that Clinton had lost the biscuit for several months without informing anyone.

"That's a big deal," Shelton wrote, "a gargantuan deal."

The president does not need approval from anyone else, including Congress or the military, to authorize a strike — a decision that might have to be made at a moment's notice.

Nevertheless, some politicians have called for more layers of approval.

"The longer I'm in the Senate, the more I fear for a major error that somebody makes," Sen. Dianne Feinstein, D-Calif., said in 2016. "One man, the president, is responsible. He makes an error and, who knows, it's Armageddon."

— How would Kim order a strike?

Much of North Korea's nuclear program is shrouded in mystery.

Kim, however, is the undisputed ruler of his isolated country. Any decision to initiate an attack would most likely be his alone. In recent months, Kim has threatened to ignite an "enveloping fire" of missiles near the Pacific island of Guam, a U.S. territory, and has warned that North Korean intercontinental ballistic missiles are capable of reaching the U.S. mainland.

"It's not a mere threat but a reality that I have a nuclear button on the desk in my office," Kim said in a speech on Monday. "All of the mainland United States is within the range of our nuclear strike."

It is doubtful that there really is a button on his desk. Furthermore, an intercontinental attack from the North probably could not happen in minutes, let alone seconds.

The North's longest-range missiles are believed to be powered by liquid rocket fuel. That means the missiles cannot be stored and ready-to-fire at a moment's notice. They must be loaded with fuel before launch, a process than can take hours.

Newer, shorter-range missiles, are loaded with solid fuel, however, making them easier to launch before the North's enemies detect an attack.