If a random individual is determined to commit a violent crime — and is willing to die in the process — there’s not a lot we can do to stop it. That’s one of the lessons learned in the fifteen years since 9/11; a period during which we’ve gotten a lot better at deterring major terrorist acts, and had to come to terms with lone wolf actors directly tied to (or merely inspired by) terror groups. In an Atlantic cover story, Steven Brill looks at the state of our safety after spending more than $1 trillion trying to boost it. Are we safer? “Our defenses are far stronger, but what we have to defend against has outpaced our progress.”