Named for the number of Spartan warriors who defended Greece at the Battle of Thermopylae, the 300 soldiers of the United States Army's 100th Missile Defense Brigade and 49th Missile Defense Battalion utilize cutting-edge technology to shield 330 million Americans against any potential nuclear threat. In locations ranging from Fort Greely, Alaska to Schriever Air Force Base, Colorado, the 300 maintain a complex—and occasionally unreliable—defense system that scientists and engineers are always improving and upgrading. With unprecedented access to the highly classified U.S. Northern Command in Cheyenne Mountain, Daniel Wasserbly reveals the incredible true story behind the 300's efforts prevent nuclear catastrophe.