Command and Control (8 page)

Unlike most presidents, Truman had firsthand experience of battle. During the First World War, half of the men in his infantry division were killed or wounded during the Meuse-Argonne offensive. Standing amid piles of dead American soldiers, the sergeant of his platoon had yelled at the survivors:
“Now . . . you'll believe you're in a war.” Truman took no pleasure in the deaths of Japanese civilians. But he preferred them to the deaths of young American servicemen. Atomic bombs, he decided, would be dropped on Japan as soon as they were ready.

The Trinity test had been preceded by weeks of careful preparation, and every effort had been made to control the outcome. The device had been slowly and patiently assembled. The wiring and explosives had been repeatedly checked. The tower had been built, the location of the test chosen, and each step of the countdown arranged as part of an elaborate, scientific experiment. Turning an experimental device into an operable weapon presented a new set of challenges. Atomic bombs had to be dropped, somehow, and American aircrews had to survive the detonations. B-29 bombers were secretly retrofitted so that nuclear weapons would fit inside them. And pilots were secretly recruited to fly these “Silverplate” B-29s. They practiced dropping dummy bombs, then banking steeply to escape the blast. Enough fissile material for two nuclear weapons—a gun-type device loaded with uranium-235 and an implosion device with a plutonium core—were readied for use against Japan. The arming and fuzing mechanisms of the bombs would determine when they exploded, whether they exploded, and how much time the bomber crews would have to get as far away as possible.

Both designs relied on the same three-stage fuzing system. When a
bomb was released at an altitude of about 30,000 feet, arming wires that linked it to the plane would be pulled out, starting a bank of spring-wound, mechanical clocks inside the weapon. After fifteen seconds, the clocks would close an electrical switch and send power to the firing circuits. At an altitude of 7,000 feet, a set of barometric switches, detecting the change in air pressure, would close another circuit, turning on four radar units, nicknamed “Archies,” that pointed at the ground. When the Archies sensed that the bomb was at an altitude of 1,850 feet, another switch would close and the firing signal would be sent. In the gun-type device, that signal would ignite small bags of cordite, a smokeless gunpowder, and shoot one piece of uranium down the barrel at the other. In the implosion device, the firing signal would set off the X-units. Both bomb types were rigged to detonate about 1,800 feet above the ground. That was the altitude, according to J. Robert Oppenheimer, “appropriate for
the maximum demolition of light structures.” Had the bombs been aimed at industrial buildings, instead of homes, the height of the airburst would have been set lower.

The arming and fuzing mechanisms were repeatedly tested at a bombing range in Wendover, Utah. At the end of a successful test the dummy bomb released a puff of smoke. But no amount of practice could eliminate fears that a real atomic bomb might detonate accidentally. Oppenheimer was especially concerned about the risk. “
We should like to know whether the take-off can be arranged,” he wrote to a USAAF liaison officer in 1944, “at such a location that the effects of a nuclear explosion would not be disastrous for the base and the squadron.” The implosion bomb could be inadvertently set off by a fire, a bullet striking an explosive lens, a small error in assembly.

If a B-29 carrying an implosion bomb was forced to return to its base,
the president's Target Committee decided that the crew should jettison the weapon into shallow water from a low altitude. The emergency procedure for a gun-type bomb was more problematic. The gun-type bomb was likely to detonate after a crash into the ocean. Water is a neutron moderator, and its presence inside the bomb would start a chain reaction, regardless of whether the two pieces of uranium slammed together. “
No suitable jettisoning ground . . . has been found,” the committee concluded in May
1945, “which is sufficiently devoid of moisture, which is sufficiently soft that the projectile is sure not to seat from the impact, and which is sufficiently remote from extremely important American installations whose damage by a nuclear explosion would seriously affect the American war effort.” The best advice that the committee could give was hardly reassuring to aircrews, whose bombing runs traversed the Pacific Ocean for thousands of miles:
try to remove the cordite charges from the bomb midair and make sure to crash the plane on land.

Captain William S. Parsons was selected to be the “
bomb commander and weaponeer” for the first military use of a nuclear weapon. A naval officer who'd spent years researching bomb fuzes, Parsons was chief of the Manhattan Project's ordnance division. At Los Alamos he'd supervised development of the gun-type bomb, which was to be dropped on the city of Hiroshima. Code-named “Little Boy,” the bomb was ten feet long and weighed about 10,000 pounds. It contained almost all the processed uranium in existence, about 141 pounds. The relative inefficiency of the design was offset by its simplicity. Although a gun-type bomb had never been tested, Oppenheimer assured Parsons that the odds of “
a less than optimal performance . . . are quite small and should be ignored.”

The bomb was assembled in an air-conditioned shed on the island of Tinian, where the Silverplate B-29s of the 509th Composite Group were based. Tinian had the largest, busiest airfield in the world, located 1,300 miles southeast of Tokyo and constructed within months of its capture from the Japanese the previous year. The four main runways were a mile and a half long. At the insistence of General Groves, the Manhattan Project's dedication to secrecy was so rigorous that even the Army Air Forces officer who commanded Tinian was not told about the atomic bomb or the mission of the unusual B-29s stationed there. Worried that a nuclear accident might kill thousands of American servicemen and destroy an airfield crucial to the war effort, Captain Parsons decided, without informing Groves, that the final steps of assembling Little Boy would not be completed until the plane carrying it had flown a safe distance from the island.

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.

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.