Free Online HD YesMovies. In 1945, US forces dropped an atomic bomb on Nagasaki. Last year, photos and a map of the aftermath were found, detailing the bomb's destructive mechanism. They showed how the Mach stem - a shock wave that hyper-intensified the power of the initial blast - was responsible for destroying buildings with increasing force 500 meters from ground zero. Through a simulation of the blast and interviews with survivors, this program reveals how the bomb was exploded to maximize its catastrophic effect.