President Trump doesn't really have a "nuclear button" on his desk to launch nuclear missiles, but if needed, he can do so on short notice from anywhere.
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Always accompanying the president is a military officer who carries a satchel known as the nuclear “football.”
The briefcase contains codes that verify the president's identity to U.S. Strategic Command (STRATCOM), which would then initiate launch procedures for intercontinental ballistic missiles armed with nuclear warheads.
The briefcase also contains what's called a “black book” that contains pre-selected nuclear options for the president to choose from for a particular response.
STRATCOM has its own copy of the "black book" stored in a safe at its command center at Offutt Air Force Base in Omaha, Nebraska.
But a president's orders can be carried out only after he reads out loud numbers on a card known as "the biscuit," supposed to be carried by the president at all times. The numbers on that card identify him as the Commander in Chief.
Last fall, Adm. Cecil Haney, the former commander of U.S. Strategic Command, told CBS's "60 Minutes" that communication lines are always open to reach the president.
Former Defense Secretary William Perry also told "60 Minutes" that if the United States came under a nuclear missile attack the president would have fewer than ten minutes to decide on a potential response.
Once an order to carry out a nuclear strike is sent, the orders have to be validated by the nuclear launch officers in silos, submarines and bomber aircraft-- using other specialized code manuals.
The United States currently has 1,393 nuclear warheads deployed on ICBMs, submarines and heavy bombers. The US also has non-deployed and inactive warheads that, when added to the deployed warheads, raises to 4,571 the total number of warheads in the U.S. nuclear arsenal (according to latest figures from the end of 2015.)
In November, General John Hyten, the current STRATCOM commander, told a security forum in Canada that under the Law of Armed Conflict, which applies to all military personnel, he could refuse an order to launch missiles if he determined it to be an "illegal" order.
"The way the process works is this simple: I provide advice to the President. He’ll tell me what to do and if it’s illegal, guess what’s going to happen?," said Hyten. " I’m going to say, Mr. President, it’s illegal. And guess what he’s going to do? He’s going to say what would be legal? And we’ll come up with options of a mix of capabilities to respond to whatever the situation is. And that’s the way it works."
Presidents are briefed on the launch procedures before they are inaugurated. In President Trump's case, a U.S. official said it occurred "very late in the transition."
Amazingly, even with all the security fail-safes, it is apparently possible for the "biscuit" to be misplaced.
That's according to General Hugh Shelton, a former chairman of the Joint Chiefs of Staff, who wrote in his 2010 autobiography "Without Hesitation; The Odyssey of an American Warrior," that the card had been misplaced for months when President Clinton was in office.
"At one point during the Clinton administration—and until this day, to my knowledge this has never been released—the codes were actually missing for months," wrote Shelton. "This is a big deal— a gargantuan deal."
Former President Clinton's office had no comment at the time when asked about Shelton's claims.