In only one scenario could the world as we know it end in a matter of hours: that is nuclear war. And one of the triggers for that war would be a nuclear missile inbound towards the United States. Every generation, a journalist has looked deep into the heart of the nuclear military establishment: the technologies, the safeguards, the plans, and the risks. These projects are vital to how we understand the world we really live in: where one nuclear missile begets one in return; where the choreography of the world’s end requires massive decisions made on seconds-notice, with information that is only as good as the intelligence we have. This book explores this ticking clock scenario, based on dozens of new interviews with military and civilian experts who have built the weapons; created the response plans; and been responsible for those decisions should they need to have been made.