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. The atom bomb exploded at about 1,900 feet above the centre of Hiroshima. The devastation was cataclysmic. Immediate casualties, dead and injured, numbered approximately 115,000....