Making of the Atomic Bomb

by Richard Rhodes

  Nobuuji: If uranium is to be used as an explosive, 10 kg is required. Why not use 10 kg of a conventional explosive?

  Nishina: That’s nonsense.

  A B-29, specially modified, first dropped an atomic bomb—a dummy Thin Man—at Muroc Army Air Force Base in California on March 3, 1944. Restrained by sway-bracing, a bomb hung singly in the B-29’s bomb bay from a single release, and the first series of tests ended ignominiously that season when a release cable loosened and dumped one onto closed bomb-bay doors at 24,000 feet. “The doors were then opened,” a technical report notes, “and the bomb tore free, considerably damaging the doors.”2178 A second series of tests in June went better. Word that Fat Man would be heavier than previously estimated encouraged Norman Ramsey’s Delivery group to replace the original bomb-release mechanism, which had been modified from a standard glider tow release, with a sturdier British Lancaster bomber design.

  Lessons learned, the Air Force began modifying seventeen more B-29’s at the Glenn L. Martin plant in Omaha, Nebraska, in August; that month the service prepared to train a special group to deliver the first atomic bombs. The 393rd Bombardment Squadron, then based at Fairmont, Nebraska, in training for Europe, would form the nucleus of the new organization. Late in August Henry H. (“Hap”) Arnold, the commanding general of the U.S. Army Air Forces, approved the assignment of an Illinois-born lieutenant colonel, Paul W. Tibbets, twenty-nine years old, to be group commander.

  Tibbets may well have been the best bomber pilot in the Air Force. He had led the first B-17 bombing mission from England into Europe, had carried Dwight Eisenhower to his Gibraltar command post before the invasion of North Africa and had led the first bomber strike of that invasion. More recently he had been test-piloting the B-29, which in 1944 was just beginning to come on line, working with the physics department of the University of New Mexico in Albuquerque to determine how well the new bomber could defend itself against fighter attack at high altitude. He was a man of medium height and stocky build with dark, wavy hair and a widow’s peak, full-faced and square-jawed, a pipe smoker. His father was a candy wholesaler in Florida and a disciplinarian from whom Tibbets probably acquired his reserved perfectionism; he was closer to his mother, the former Enola Gay Haggard of Glidden, Iowa. He had chosen an Air Force career, he told a postwar interviewer, after his mother had supported him in that choice against his father’s opposition:

  When I was in college, studying to be a doctor, I realized that I had always wanted to fly. In 1936, my desire to do something about it reached the point where a family showdown on the subject developed. During the discussion, a few tempers flared, but my mother never said a word. In the end, still undecided, I got her off to the side and asked her what she thought. Despite the things that had been said on the subject, and the fact that most of the people in the discussion had included the statement, “You’ll kill yourself in an airplane,” Mother said, quite calmly and with positive assurance, “You go ahead and fly. You will be all right.”2179

  So far he had been, and now he had won a new assignment. He flew to Second Air Force headquarters in Colorado Springs at the beginning of September 1944 to report to commanding Major General Uzal Ent. An aide installed him in the general’s anteroom. An officer came out, introduced himself, took Tibbets aside and asked him if he had ever been arrested. Tibbets considered the situation and decided to answer honestly to this stranger that he had been, as a teenager in North Miami Beach, caught in flagrante delicto in the backseat of a car with a girl. Lieutenant Colonel John Lansdale, Jr., who was responsible to Groves for atomic bomb intelligence and security, knew about the arrest and had questioned Tibbets to test his honesty. Now he led him into Ent’s office. Norman Ramsey and Deke Parsons were waiting there. “I’m satisfied,” Lansdale said.2180 The physicist and the Navy officer briefed Tibbets on the Manhattan Project and the Muroc bombing tests. Lansdale cautioned him at length on security. After the three men left, Ent specified Tibbets’ assignment. “You have to put together an outfit and deliver this weapon,” the pilot remembers the Second Air Force commander saying. “We don’t know anything about it yet. We don’t know what it can do. . . . You’ve got to mate it to the airplane and determine the tactics, the training, and the ballistics—everything. These are all parts of your problem. This thing is going to be very big. I believe it has the potential and possibility of ending the war.”2181 The delivery program within the Air Force had been codenamed Silverplate, Ent told him. If Tibbets needed anything, he had only to use that magic word; Arnold had accorded it the highest priority in the service.

  The Air Force chose Wendover Field, Utah, as home base for the new organization.2182 Tibbets flew to Utah early in September, looked the base over and liked what he saw. It was sited between low mountain ranges on the desert salt flats in gritty and secure isolation 125 miles west of Salt Lake City near the Utah-Nevada border; the flat basin, the sink of an ancient and enormous freshwater lake of which the Great Salt Lake is a brackish remnant, offered miles of desolation for bombing practice. Pioneers bound for California had suffered the crossing once—their wagon ruts could still be viewed nearby. The 393rd moved to Wendover in September and with the addition of troop-carrier and other support components became the 509th Composite Group. In October it began receiving its new B-29’s.2183

  A Boeing product, the B-29 was a revolutionary aircraft, the first intercontinental bomber. It was conceived in the late 1930s by ambitious officers within what was then still the Army Air Corps as the vehicle of their vision of wars fought at great distance by strategic air power. As early as September 1939 they proposed its use from bases in the Philippines, Siberia or the Aleutians in the event of war against Japan.2184 It was the world’s first pressurized bomber and at 70,000 pounds the heaviest production bomber ever built, 135,000 pounds loaded, a weight that required an 8,000-foot runway to lumber airborne. In appearance it was a sleek, polished-aluminum tube 99 feet long intersected by huge 141-foot wings—two B-29’s would fill a football field—with a classic sinusoidal tail nearly three stories tall. Four Wright 18-cylinder radial engines that each developed 2,200 horsepower propelled it at altitude at 350 miles per hour maximum speed—it cruised at 220—and it was designed to fly a 4,000-mile mission with up to 20,000 pounds of bombs, though 12,000 pounds was nearer its operational load. It could cruise above 30,000 feet, out of range of flak and of most enemy fighters. Turbosuperchargers boosted engine power; outsized 16.5-foot propellers turned more slowly than those of any other aircraft; wing flaps, the world’s largest, adjusted a fifth of wing area to adapt the high-speed, long-range, low-drag wing for takeoff and landing.

  On the ground the B-29 rested level on three point landing gear: retractable wheels at the nose and under each wing. The plane’s eleven-man crew occupied two pressurized sections within the five joined sections of the fuselage; tandem bomb bays fore and aft of the wings separated the nose section from the waist and tail, and to pass back from the nose to the waist required crawling through a pressurized one-man tunnel. The standard B-29 crew counted pilot, copilot, bombardier, flight engineer, navigator and radio operator in the nose section, three gunners and a radar operator in the waist and another gunner in the tail. Because electrical wiring was less vulnerable to battle damage than pneumatic or hydraulic tubing, the aircraft systems with the exception of the hydraulic wheel brakes operated entirely on electric motors, more than 150 in all, with a gasolinepowered donkey engine in the rear fuselage supplying current on the ground. Analog computers ran a central gun-control system, but all the guns were stripped from 509th bombers except the 20-millimeter cannon in the tail.

  If the B-29’s engines were powerful they were also notoriously susceptible to fires. To improve their horsepower-to-weight ratio Wright had used magnesium for their crankcases and accessory housings. Engine cooling was inadequate and exhaust valves tended to overheat and stick; an engine would then sometimes swallow a valve and catch fire. If the fire reached the magnesium, a metal comm
only used in incendiary bombs, the engine would usually burn through the main wing spar and peel off the wing. To prevent such disasters Boeing improved engine cooling but the basic design fault persisted; there was no time to develop a new power plant if the aircraft was to serve the war for which it was invented. (One Delivery group physicist remembers skimming along at Wendover for miles after takeoff, mowing sagebrush, to cool the engines before climbing to altitude.2185)

  Once at altitude the flight crews of the 509th practiced bombing runs, bombardiers aiming from above 30,000 feet through their Norden bombsights at progressively smaller target circles limed on the ground. Crews that had flown in cloudy Europe wondered why they were training in visual bombing; an odd evasive maneuver instructed them at least in the explosive potential of the unknown weapon they would carry. Tibbets briefed no one on the atomic bomb but directed his crews to nose their aircraft over into a sharp 155-degree diving turn immediately after bomb release. Diving the huge bombers rapidly increased their airspeed; by perfecting the maneuver the crews could escape ten miles from the delayed explosion, “safe from destruction” by a bomb of 20,000 tons TNT equivalent, writes Groves, “by a factor of two.”2186 Before they practiced their diving turns they dropped bombs of concrete and bombs filled with HE. These crudely riveted Fat Man imitations, painted bright orange for visibility, they called Pumpkins. The 509th worked hard; the winter wind howled over the Wendover reservation, trapping tumbleweeds on the barbed-wire fences; crews careened into Salt Lake City on weekends to blow out. Tibbets opened their mail, bugged their telephones, had them followed and shipped off those who broke security to the secure but miserable Aleutians for the duration of the war.2187 He held authority over 225 officers and 1,542 enlisted men. With his silverplated requisitions he commandeered from around the world the best pilots, bombardiers, navigators and flight engineers he could find.

  One of them, Captain Robert Lewis of Brooklyn, New York, stocky and blond, twenty-six years old, an abrasive but gifted pilot whom Tibbets had personally trained, had spent part of the summer of 1944 at Grand Island, Nebraska, teaching a senior officer with hundreds of combat hours behind him to fly B-29’s. Thus checked out, Major General Curtis LeMay rode a C-54 to India late in August to take over the 20th Bomber Command, based in India with forward airfields in China from which it was attempting with fewer than two hundred B-29’s to bomb Japan. The bombers had to ferry their own fuel and ordnance from India to China over the Himalayas before each mission—seven supply flights for each bombing strike, up to twelve gallons burned for each one gallon delivered. “It didn’t work,” LeMay writes in his autobiography. “No one could have made it work. It was founded on an utterly absurd logistic basis. Nevertheless, our entire Nation howled like a pack of wolves for an attack on the Japanese homeland.”2188

  Curtis LeMay was a wild man, hard-driving and tough, a bomber pilot, a big-game hunter, a chewer of cigars, dark, fleshy, smart. “I’ll tell you what war is about,” he once said bluntly—but he said it after the war—“you’ve got to kill people, and when you’ve killed enough they stop fighting.”2189 Through most of the war he seems to have held to the preference for precision bombing over area bombing that had distinguished the U.S. Air Force from the British since Churchill’s and Cherwell’s intervention of 1942. Sometimes in Europe precision bombing had served, though never decisively. Over Japan, so far, it had failed. And failure was LeMay’s bete noire.

  His father had been a failure, an odd-job drifter, forever moving his family around. The LeMays lived all over Ohio, in Pennsylvania, out in the wilds in Montana, in California. Curtis Emerson LeMay, born in Columbus, Ohio, in 1906, was the first of seven children. The two memories of early childhood he chooses to offer in his autobiography are linked. Of first seeing an airplane and chasing it madly: “I wanted not only the substance of the mysterious object, not only that part I could have touched with my hands. I wished also in vague yet unforgettable fashion for the drive and speed and energy of the creature.”2190 And of compulsively running away from home: “truancy” that “bordered on mania,” his mother told him.2191 “I had to grow older,” LeMay writes, “and be burdened with a lot of responsibilities, and begin to nourish ambition—I had to do these things before I could manage to control my temper and discipline my activities.”2192

  He delivered telegrams and packages and boxes of candy. He delivered newspapers, sold newspapers, wholesaled newspapers to delivery boys, supporting himself and sometimes his family: “When the grocer hesitates about putting that latest basket of groceries on the bill, then you’d better be ready to come up with cash in hand. Very early in life I was convinced bitterly of this necessity. . . . The larder was a vague mystery which Pop didn’t bother to penetrate.”2193 LeMay resented the missing childhood but moved on. He paid his own way through Ohio State by working nights at a steel foundry. ROTC in college led to the Ohio National Guard because the Guard had higher priority on Army flying-school enrollments than the Army Reserve. He won his wings in 1929 and never looked back: mess officer, navigation officer, General Headquarters navigator, B-10’s, B-17’s. In England in 1943 and 1944 he worked night and day to improve precision bombing. He won quick promotion.

  Arnold sent him to the Pacific because he needed someone who could get the job done:

  General Arnold, fully committed to the B-29 program all along, had crawled out on a dozen limbs about a thousand times, in order to achieve physical resources and sufficient funds to build those airplanes and get them into combat. . . . So he finds they’re not doing too well. He has to keep juggling missions and plans and people until the B-29s do do well. General Arnold was absolutely determined to get results out of this weapons system.2194

  The B-29 had to be used, that is, successfully used, or men who had staked their careers and their convictions would be shamed, resources squandered that might have aided elsewhere in the war, lives lost futilely and millions of dollars wasted. The justification recurs.

  The first B-29 to arrive in the Marianas landed on Saipan on October 12, 1944. Brigadier General Haywood S. Hansell, Jr., assigned to lead the 21st Bomber Command, flew it. As Arnold’s chief of staff Hansell had helped formulate the doctrine of precision bombing and believed strongly in its central premise—that wars could be won by selectively destroying the enemy’s key industries of war.2195, 2196 A stream of new bombers followed the new commander out to the Marianas; the first U.S. aircraft to fly over Tokyo since the Doolittle raid of 1942 was a B-29 on November 1 soaring high and light on a photoreconnaissance mission. A French journalist living in Tokyo at the time, Robert Guillain, remembers his sense of anticlimax:

  The city waited. Millions of lives were suspended in the silence of the radiant autumn afternoon. For a moment, antiaircraft fire shook the horizon with a noise of doors slamming in the sky. Then—nothing: the all-clear was sounded without sight of a plane. The radio announced that a single B-29 had flown over the capital without dropping any bombs.

  That seemed a reprieve and for a time only reconnaissance missions disturbed the ill-defended city. “One day the visitor finally appeared, flying at 35,000 feet,” Guillain continues; “he even left his signature chalked on the blue sky: a line of pure white like some living thing that seemed to nose an almost imperceptible silver fly ahead of it.” Back in the Marianas Hansell was teaching his men to navigate together, to fly in formation; they had trained in the United States only as individual crews.

  Hansell received his first target directive on November 11. The Joint Chiefs of Staff had approved it and it reflected their conviction that bombing and naval blockade alone could not bring the Pacific war to a timely end. In September the Combined Chiefs—British and American together—had established a planning date for the end of the war: eighteen months after the defeat of Germany. The U.S. Joint Chiefs judged an invasion of the Japanese home islands essential to achieve that goal. The target directive Hansell received therefore gave first priority to the precision bombing of the Japan
ese aircraft industry (to cripple Japanese air defenses before an American invasion), second priority to supporting Pacific operations (MacArthur was even then reoccupying the Philippines, returning as he had promised he would) and third priority to testing the efficacy of area incendiary attacks. These priorities, putting precision bombing first, suited Hansell’s own.

  His crews flew their first raid on Japan from Saipan on November 24. Their target was the Musashi aircraft engine factory north of Tokyo ten miles from the Imperial Palace. A hundred planes began the mission. Seventeen aborted; six were unable to release their bombs. Flak was heavy and the target buried in undercast. But totally unexpected at the high altitude at which the bombers flew was a 140-mile-per-hour wind. They were blown with it over the target and their ground speed was therefore nearly 450 mph, impossible for the bombardiers. As a result only twenty-four planes managed to bomb the factory area—the rest scattered their loads over the docks and warehouses around Tokyo Bay—and only sixteen bombs hit the target. “I did not anticipate the extremely high wind velocities above thirty thousand feet,” Hansell said later, “and they came as a very disagreeable surprise.”2197 The Air Force had discovered the jet stream.

  LeMay was then still working with his 20th Bomber Command out of India and China. Supporting the indifferent military campaigns of Chiang Kai-shek was an activity he abhorred but was sometimes forced to perform. For six months Claire Chennault, the leathery Texan who headed the U.S. air staff assigned to the Nationalist Chinese Army, had been promoting the bombing of Hankow, the riverside city on the Yangtze five hundred miles inland from Shanghai from which Japan supplied its Asian mainland armies. With a renewed Japanese drive in interior China in November Chennault pressed for a Hankow attack. LeMay resisted diverting his command from Japanese home-island targets; the Joint Chiefs had to compel his participation. B-24’s and B-25’s were also massing for the strike; Chennault particularly wanted LeMay to load his aircraft with incendiaries and bomb from 20,000 feet rather than from above 30,000 feet in order to sow a denser pattern. LeMay reserved one aircraft in five for high explosives. Seventy-seven B-29’s took part in the raid on December 18 and burned the Hankow river district down; fires raged out of control for three days. The lesson was not lost on Washington, nor on LeMay.