This 11-minute video takes us from the preparations of the Fat Man nuclear weapon, its loading onto the plane Bockscar, and the explosion of the bomb in Nagasaki. It's a sobering look at this catastrophically destructive technology and a reminder of the toll it took in human lives.
YouTube user RestrictedData uploaded this video and provided annotations that explain exactly what is going on from shot to shot. Aside from an adjustment in the contrast, this is essentially raw footage taken from the island of Tinian and a second bomber that observed Bockscar and the explosion, archived by the Los Alamos National Laboratory. The annotations in this case are extremely helpful, although you can turn them off to experience the video by itself.