Why dropping the bomb 70 years ago was necessary, and why we need to be ready to do it again

On the morning of Aug. 6, 1945, shortly after 8:00 a.m. local time, a lone American B-29 was conducting what seemed to be a reconnaissance flight at high altitude over the Japanese city of Hiroshima. At about 16 minutes after 8:00, the aircraft released an object over the centre of town. Attached to parachutes, the object floated down slowly enough to give the four-engine Boeing Superfortress time to turn and lumber out of the airspace.