Despite attempts from his secretary of State to cool down the escalating exchange of threats between the White House and North Korea, Donald Trump and his surrogates seem determined to keep the temperature high. After doubling down on his incendiary threat to direct “fire and fury” toward North Korea, saying that “maybe it wasn’t tough enough,” Trump went a step further, announcing on Twitter that the US is ready to repel a North Korean attack:

Military solutions are now fully in place,locked and loaded,should North Korea act unwisely. Hopefully Kim Jong Un will find another path!

— Donald J. Trump (@realDonaldTrump) August 11, 2017

The US president also retweeted pictures shared by the US Pacific Command showing aircraft ready for an eventual #FightTonight mission, “if called upon to do so.”

#USAF B-1B Lancer #bombers on Guam stand ready to fulfill USFK’s #FightTonight mission if called upon to do so https://t.co/O3oVeFrNrG pic.twitter.com/IAm2qLwcWY

— U.S. Pacific Command (@PacificCommand) August 11, 2017

The situation has left “Trump antics” territory and crossed solidly into the scary zone. But does the commander in chief have the power to launch a war on his own—perhaps via Twitter? That’s a more complicated question than it might seem.

The so-called War Powers Clause of the constitution says that only once war has been declared by Congress can the president lead the military into it. However, the president does have the authority to order a nuclear attack, not only in retaliation but also as a preemptive measure (pdf, p.1) to stop an attack on US territories. The system in place for deploying the US’s more than 7,000 nuclear warheads was developed during the cold war and rests on a core element: The president, and only the president, has the authority to authorize a strike, and nobody can legally veto him.

Still, that doesn’t mean his decision will get carried out without question or that the chain of command can’t interfere. This is how the president would launch an attack, according to assorted published reports. (Spoiler: Twitter is not involved.)

  1. Get out the biscuit: The president holds the nuclear codes, called the “gold codes,” on a laminated card called “the biscuit” that he carries. New codes are provided daily by the National Security Agency (NSA). The biscuit includes a number of fake codes, so the president has to memorize where the right ones are located.
  2. Get the football: The “football” is the briefcase containing secure communications equipment as well as instructions on how to verify the president’s identity and transmit the command. The football is carried around by a military aide who is always near the president.
  3. Order an attack: Once his identity has been verified, the president can order an attack—though the details of how he does it are secret.
  4. Execution: The secretary of Defense is notified of the order, but isn’t legally required to give approval for the attack, and doesn’t have the power to veto it; nor does anyone else in the chain of command. The system is designed to launch within minutes of the president’s order. Still, officials might find ways to delay or impede what they thought were rash decisions, as two of president Richard Nixon’s (paywall) Defense secretaries did.

All this, however, is in theory. Whether or not the many people involved in launching a military attack would cooperate with an impulsive presidential decision remains to be seen—and hopefully, never will be.