Why a mysterious black briefcase follows the US president everywhere

According to Bill Gulley, a former director of the White House Military Office, the ubiquitous Football does not contain a doomsday red-button keypad but rather four items:
  • a 75-page black book of retaliatory nuclear-strike options printed in black and red ink 
  • another black book with a list of classified sites to shelter the president 
  • a manila folder containing 10 pages of instructions on how to operate the Emergency Broadcast System 
  • an index card with authentication codes 
via businessinsider.com