What are the nuclear codes?

An FBI raid on former President Donald Trump's home was motivated in part by a hunt for documents related to nuclear weapons, The Washington Post reported Thursday (Aug. 11), spurring chatter from media commentators and on social media that Trump may have inappropriately held on to the nuclear codes. 

The anonymous sources cited by the Post did not specify what kind of "nuclear documents" the FBI was looking for in the raid on Trump's Mar-a-Lago estate in Florida, and the FBI has not said what documents were found. According to The Post, documents laying out information about the U.S. nuclear program or another country's nuclear capacity could be dangerous for international security. For example, another country might view having its nuclear secrets exposed as a threat.

In that sense, the nuclear codes might be one of the less worrisome discoveries for the FBI to make. Even if Trump did hold on to the nuclear codes, they wouldn't be useful for authorizing an attack now, because the codes change frequently. So what are the nuclear codes, where are they located and what's the process of launching a nuclear attack? 

There are two sets of codes required for a nuclear launch: the ones used by launch crews to enable and fire the nuclear weapons, and the ones used by the president to authorize such an attack. The president does not have access to the first set, according to the Brookings Institution; those are kept on military bases and at the Pentagon. 

Related: How many nuclear weapons exist?

The codes the commander-in-chief has are also known as the Gold Codes. They identify the president and confirm the president's authority to order a nuclear attack. These codes are printed on the Biscuit, a credit-card-sized slip of plastic. According to Bloomberg, if the president decides to authorize an attack, a senior military official reads aloud a "challenge code," which might be a few letters from the military alphabet. The president consults the Biscuit, finds the code starting with those letters and reads the rest of the code.

The Biscuit is part of the kit known colloquially as the Football, or the Nuclear Football but officially called the president's "emergency sachet." The sachet also contains the so-called Black Book, which lists the president's options for a strike — destroy everything, or hit just one or two cities? — as well as other emergency procedures. This briefcase is carried by an aide who remains near the president at all times. 

The Football dates back to the Kennedy administration, according to Smithsonian Magazine, and was first photographed in May 1963 trailing the president. It does, on occasion, become separated from the commander-in-chief. After President Ronald Reagan was shot, for example, he was whisked to the hospital and separated from the Football-carrying aide. Reagan's Biscuit was also separated from him, as it was in the pocket of his clothing that was sheared off to prepare the president for emergency surgery, according to a 1981 The Washington Post report. The FBI ultimately took possession of the card. In 2010, Hugh Shelton, chairman of the Joint Chiefs of Staff during the Clinton administration, claimed that President Bill Clinton lost his Biscuit for several months in 2000 — a potentially serious mishap that went unreported until it was time to change the codes (which was reportedly done every four months at the time). 

If the president were Biscuit-less in a nuclear emergency, the responsibility for launching a nuclear attack would fall to the next in command, the vice president, who has backup identification codes and a backup Football, The Atlantic reported in 2010. This chain of command is designed to work if the commander-in-chief is killed or incapacitated, but it would likely lead to delays and bureaucratic chaos if the president were well but could not be formally identified, according to The Atlantic.

Typically, the Football is passed from an outgoing president to the next president at the inauguration, at which time the Gold Codes change. Because Trump did not attend the inauguration of Joe Biden, however, the military came up with an alternative plan involving one emergency sachet that flew with Trump to Florida as he left the White House and another handed to Biden's aide at the inauguration. According to CTV News Canada, Trump's codes expired at noon on inauguration day, and Biden's became active.

Originally published on Live Science.