National security

Nervous about nukes again? Here’s what you need to know about The Button. (There is no button.)

It follows the president everywhere — onto Air Force One, onto the golf course, onto elevators. Inside is a manual for conducting nuclear war. A how-to, really.

The briefcase is aluminum, 45 pounds, clad in leather and descends from a line of durable, airtight cases made specially for Erle P. Halliburton, the oil-field engineer who founded the company that would become infamous because of its associations with Dick Cheney, the Iraq war and the Deepwater Horizon oil leak.

Carrying the briefcase is a job shared among five military aides, one from each branch of the U.S. armed forces. The manual inside is more like a takeout menu, but instead of picking between numbered Chinese dishes, the president would choose cities or military installations in, say, Russia or China (or both) to attack.