Command and Control

At three in the morning on August 6, 1945, Parsons and another weaponeer, Morris Jeppson, left the cockpit and climbed into the bomb bay of a B-29 named Enola Gay, after the pilot’s mother. The plane was flying at an altitude of five thousand feet, about sixty miles off the coast of Tinian. After making sure that three green safing plugs were inserted into the bomb, Parsons unscrewed the back of it while Jeppson held a flashlight and air turbulence bounced the plane. Nobody had ever done this procedure to a weapon containing fissile material, let alone to one dangling from a single hook in a darkened bomb bay. The men kneeled on a narrow aluminum platform that had been installed the previous day. It took Parsons about twenty minutes to put four small silk bags of cordite into the breech of the gun barrel, reattach the primer wires, and close the back of the bomb. Four and a half hours later, Jeppson returned to the bomb bay alone. The plane was now at about nine thousand feet, nearing the coast of Japan, and the bomb bay felt a lot colder. The green safing plugs blocked the electrical circuit between the fuzing system and the cordite. Jeppson replaced them with red arming plugs. Little Boy was now fully armed, drawing power from its own batteries and not from the plane.

The city of Hiroshima spread across half a dozen islands in the delta of the Ota River. Much of the population had fled to the countryside, leaving about three hundred thousand people in town. The aiming point for Little Boy was the Aioi Bridge, far from the industrial plants on the other islands. The bridge lay in the heart of the city, near the headquarters of the Second Army, amid a residential and commercial district. The bomb was dropped from the Enola Gay at about 8:16 A.M., fell for about forty-four seconds, and detonated at an altitude of roughly 1,900 feet.

At ground zero, directly beneath the airburst, the temperature reached perhaps 10,000 degrees Fahrenheit. Everyone on the bridge was incinerated, and hundreds of fires were ignited. The blast wave flattened buildings, a firestorm engulfed the city, and a mushroom cloud rose almost ten miles into the sky. From the plane, Hiroshima looked like a roiling, bubbling sea of black smoke and fire. A small amount of fissile material was responsible for the devastation; 98.62 percent of the uranium in Little Boy was blown apart before it could become supercritical. Only 1.38 percent actually fissioned, and most of that uranium was transformed into dozens of lighter elements. About eighty thousand people were killed in Hiroshima and more than two thirds of the buildings were destroyed because 0.7 gram of uranium-235 was turned into pure energy. A dollar bill weighs more than that.

The Trinity test had been kept secret, the bright flash in the desert dismissed by the War Department as an explosion at an ammunition dump. But the need for secrecy had passed, and publicity about the new weapon would send a clear message about America’s military strength not only to Japan but also to the Soviet Union. On August 6, President Truman announced that an atomic bomb, harnessing “the basic power of the universe,” had just destroyed Hiroshima. “We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city,” Truman warned. “If they do not now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this earth.” But the Japanese government still would not agree to an unconditional surrender, insisting that the emperor be allowed to remain on his throne. The day after Hiroshima’s destruction, the governor of the local prefecture encouraged survivors to find “an aroused fighting spirit to exterminate the devilish Americans.”

Meanwhile, another atomic bomb, nicknamed “Fat Man,” was being assembled at a special building on Tinian. The floor of the building had been coated with rubber and lined with copper wire to minimize the chance that static electricity would cause a spark. The bomb was a Mark 3 implosion device, and putting it together presented more of a challenge than the assembly of Little Boy. Captain Parsons compared the effort to “rebuilding an airplane in the field.” Fat Man was scheduled for delivery on August 11, with the city of Kokura as its target. The prospect of bad weather moved the date forward to the ninth.