Command and Control by Eric Schlosser Page A

told his vice president, Harry Truman, about the Manhattan Project or the unusual weapon that it was developing. When Roosevelt died unexpectedly, on April 12, 1945, Truman had the thankless task of replacing a beloved and charismatic leader during wartime. The new president was unlikely to reverse a nuclear policy set in motion years earlier, at enormous expense, because a group of relatively unknown scientists now considered it a bad idea.Truman’s decision to use the atomic bomb was influenced by many factors, and the desire to save American lives ranked near the top. An invasion of Japan was scheduled forNovember 1. Former President Herbert Hoover warned Truman that such an invasion would costbetween “500,000 and 1,000,000 American lives.” At the War Department, it was widely assumed thatAmerican casualties would reach half a million. During the recent battle of Okinawa,more than one third of the American landing force had been killed or wounded—and a full-scale invasion of Japanmight require 1.8 million American troops. While meeting with the Joint Chiefs of Staff in June 1945, Truman expressed the hope of avoiding “an Okinawa from one end of Japan to the other.”
    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 abomb 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,