Regrets—we’ve all had a few. L’esprit de l’escalier—that wonderful line coming to mind a moment too late—is a common annoyance after failed dates and dud job interviews; dented fenders and bum shoulders attest to avoidable failures of depth perception and misjudged forays into backyard football games.

When it comes to the development of nuclear weapons by rogue states, however, regrets become rather more profound.