Command and Control

At around midnight, the night before the bomb was to be loaded onto a Silverplate B-29, a technician named Bernard J. O’Keefe noticed something wrong with the master firing cable that was supposed to connect the Archies to the X-unit. The cable and the X-unit both had female plugs. Somehow the cable had been installed backward. It would take a couple of days to disassemble the layers of spheres and explosives, remove the cable, and reinstall it properly. “I felt a chill and started to sweat in the air-conditioned room,” O’Keefe recalled. He decided to improvise. With help from another technician, he broke one major safety rule after another, propping the door open to bring in extension cords and using a soldering iron to attach the right plugs. It was risky to melt solder in a room with five thousand pounds of explosives. The two men fixed the cable, connected the plugs, and didn’t tell anyone what they’d done.

The attempt to drop Fat Man on Kokura, the site of Japan’s largest arsenal, did not go smoothly. After the bomb was loaded onto a B-29 called Bockscar, one of the plane’s fuel pumps malfunctioned before takeoff. Major Charles W. Sweeney, the twenty-five-year-old pilot commanding his first combat mission, decided to proceed with six hundred gallons of fuel inaccessible in a reserve tank. Four hours after leaving Tinian, flashing red lights on the flight test box suddenly indicated that the bomb’s fuzes had been activated. The red lights could mean the weapon was fully armed and ready to explode. Sweeney considered jettisoning the bomb over the ocean, but let Philip Barnes, the assistant weaponeer, tinker with the flight test box. Barnes quickly checked the blueprints, looked inside the box, and found that a couple of rotary switches had been set in the wrong position. The bomb wasn’t armed, and the crew was relieved to hear it.

Poor weather dogged the flight, with dark clouds and heavy turbulence. Bockscar circled for forty minutes at a rendezvous point over Japan, wasting fuel, waiting for another American plane that never arrived. Sweeney opened the bomb bay doors over Kokura, but the city was shrouded in smoke and haze. He had strict orders to drop the bomb visually, not by radar. Bockscar spent almost an hour over Kokura, made three unsuccessful bombing runs, and drew antiaircraft fire. The city was spared by the poor visibility. Sweeney had enough fuel for one run at the secondary target, Nagasaki. He dropped the bomb there, worried that the plane might have to be ditched in the ocean, and barely made it to the American air base at Okinawa.

Fat Man missed its aiming point by more than a mile. Instead of detonating above the central commercial district, the bomb went off above an industrial area on the western outskirts of Nagasaki. About one fifth of the plutonium fissioned, and the force of the explosion was equal to about 21,000 tons of TNT (21 kilotons). The bomb proved more powerful and efficient than the gun-type device used at Hiroshima, which had an explosive force of between 12 and 18 kilotons. But the damage was less severe in Nagasaki. A series of hills protected much of the city from the blast wave, and a firestorm never erupted, despite winds that reached more than six hundred miles an hour. About forty thousand people were killed in Nagasaki, at least twice that number were injured, and more than one third of the homes were destroyed. Ground zero was approximately five hundred feet south of the Mitsubishi Steel Works. According to one report, the plant was left “bent and twisted like jelly.” The bomb also leveled the nearby Mitsubishi Arms Factory, where the torpedoes fired at Pearl Harbor were made.

Most of the casualties in Hiroshima and Nagasaki resembled those caused by incendiaries and conventional bombs. About half of the victims burned to death, and about one third were killed by debris. But two new types of casualty appeared. Flash burns were caused by the extraordinarily hot, though brief, detonation of the atomic bombs. Traveling in straight lines at the speed of light, the thermal radiation was strong enough to kill everyone within a mile of ground zero who was unprotected by walls or other objects that could block ultraviolet and infrared rays. Serious burns were possible at a distance of two miles. Thick clothing offered some protection, because the flash lasted less than a second. White clothes tended to reflect thermal radiation, while darker colors absorbed it. A number of victims suffered flash burns that mimicked the dark and light patterns of their kimonos.