The nuclear football — a black briefcase containing an illustrated menu of doomsday scenarios — follows President Trump everywhere he goes. Like every U.S. commander-in-chief since John F. Kennedy, Trump has the sole authority to empty the American nuclear arsenal on any target, at any time, for any reason. James Mattis, his secretary of defense, must authenticate the order before it reaches the Pentagon, but should Mattis refuse to do so in an attempt to prevent missiles from launching, Trump can simply fire him on the spot and replace him with someone who will carry the order out.
https://fivethirtyeight.com/features/were-edging-closer-to-nuclear-war/
