Making of the Atomic Bomb

by Richard Rhodes

  Later in the afternoon they began considering targets. Groves had extended Farrell’s guidelines:

  I had set as the governing factor that the targets chosen should be places the bombing of which would most adversely affect the will of the Japanese people to continue the war.2298 Beyond that, they should be military in nature, consisting either of important headquarters or troop concentrations, or centers of production of military equipment and supplies. To enable us to assess accurately the effects of the bomb, the targets should not have been previously damaged by air raids. It was also desirable that the first target be of such size that the damage would be confined within it, so that we could more definitely determine the power of the bomb.

  But such pristine targets had already become scarce in Japan. If the first choice the Target Committee identified at its first meeting was hardly big enough to confine the potential damage, it was the best the enemy had left to offer:

  Hiroshima is the largest untouched target not on the 21st Bomber Command priority list. Consideration should be given to this city.

  “Tokyo,” the committee notes continue, “is a possibility but it is now practically all bombed and burned out and is practically rubble with only the palace grounds left standing. Consideration is only possible here.”

  The Target Committee did not yet fully understand the level of authority it commanded. With a few words to Groves it could exempt a Japanese city from Curtis LeMay’s relentless firebombing, preserving it through spring mornings of cherry blossoms and summer nights of wild monsoons for a more historic fate. The committee thought it took second priority behind LeMay rather than first priority ahead, and in emphasizing these mistaken priorities the colonel who reviewed the Twentieth Air Force’s bombing directive for the committee revealed what the United States’ policy in Japan in all its deadly ambiguity had become:

  It should be remembered that in our selection of any target, the 20th Air Force is operating primarily to laying waste all the main Japanese cities, and that they do not propose to save some important primary target for us if it interferes with the operation of the war from their point of view. Their existing procedure has been to bomb the hell out of Tokyo, bomb the aircraft, manufacturing and assembly plants, engine plants and in general paralyze the aircraft industry so as to eliminate opposition to the 20th Air Force operations. The 20th Air Force is systematically bombing out the following cities with the prime purpose in mind of not leaving one stone lying on another:

  Tokyo, Yokohama, Nagoya, Osaka, Kyoto,

  Kobe, Yawata & Nagasaki.

  If the Japanese were prepared to eat stones, the Americans were prepared to supply them.

  The colonel also advised that the Twentieth Air Force planned to increase its delivery of conventional bombs steadily until it was dropping 100,000 tons a month by the end of 1945.

  The group decided to study seventeen targets including Tokyo Bay, Yokohama, Nagoya, Osaka, Kobe, Hiroshima, Kokura, Fukuoka, Nagasaki and Sasebo. Targets already destroyed would be culled from the list. The weather people would review weather reports. Penney would consider “the size of the bomb burst, the amount of damage expected, and the ultimate distance at which people would be killed.” Von Neumann would be responsible for computations. Adjourning its initial meeting the Target Committee planned to meet again in mid-May in Robert Oppenheimer’s office at Los Alamos.

  A third level of discourse on the uses of the bomb revealed itself as Henry Stimson assembled the committee that Bush and Conant had proposed to him and he had proposed in turn to the President. On May 1, the day German radio announced the suicide of Adolf Hitler in the ruins of Berlin, George L. Harrison, a special Stimson consultant and the president of the New York Life Insurance Company, prepared for the Secretary of War an entirely civilian committee roster consisting of Stimson as chairman, Bush, Conant, MIT president Karl Compton, Assistant Secretary of State William L. Clayton, Undersecretary of the Navy Ralph A. Bard and a special representative of the President whom the President might choose. Stimson modified the list to include Harrison as his alternate and carried it to Truman for approval on May 2. Truman agreed and Stimson apparently assumed his interest in the project, but the President significantly did not even bother to name his own man to the list. Stimson wrote in his diary that night:2299

  The President accepted the present members of the committee and said that they would be sufficient even without a personal representative of himself. I said I should prefer to have such a representative and suggested that he should be a man (a) with whom the President had close personal relations and (b) who was able to keep his mouth shut.2300

  Truman had not yet announced his intention to appoint Byrnes Secretary of State because the holdover Secretary, Edward R. Stettinius, Jr., was heading the United States delegation to the United Nations in San Francisco and the President did not want to undercut his authority there. But word of the forthcoming appointment had diffused through Washington. Acting on it, Harrison suggested that Stimson propose Byrnes. On May 3 Stimson did, “and late in the day the President called me up himself and said that he had heard of my suggestion and it was fine. He had already called up Byrnes down in South Carolina and Byrnes had accepted.”2301 Bundy and Harrison, Stimson told his diary, “were tickled to death.”2302 They thought their committee had acquired a second powerful sponsor. In fact they had just welcomed a cowbird into their nest.

  Stimson sent out invitations the next day. He proposed calling his new group the Interim Committee to avoid appearing to usurp congressional prerogatives: “when secrecy is no longer required,” he explained to the prospective members, “Congress might wish to appoint a permanent Post War Commission.”2303 He set the first informal meeting of the Interim Committee for May 9.

  The membership would assemble in the wake of momentous change. The war in Europe had finally ground to an end. Supreme Allied Commander Dwight D. Eisenhower celebrated the victory on national radio the evening of Tuesday, May 8, 1945, V-E Day:

  I have the rare privilege of speaking for a victorious army of almost five million fighting men. They, and the women who have so ably assisted them, constitute the Allied Expeditionary Force that has liberated western Europe. They have destroyed or captured enemy armies totalling more than their own strength, and swept triumphantly forward over the hundreds of miles separating Cherbourg from Lübeck, Leipzig and Munich. . . .2304

  These startling successes have not been bought without sorrow and suffering. In this Theater alone 80,000 Americans and comparable numbers among their Allies, have had their lives cut short that the rest of us might live in the sunlight of freedom. . . .

  But, at last, this part of the job is done. No more will there flow from this Theater to the United States those doleful lists of death and loss that have brought so much sorrow to American homes. The sounds of battle have faded from the European scene.

  Eisenhower had watched Colonel General Alfried Jodl sign the act of military surrender in a schoolroom in Rheims—the temporary war room of the Supreme Headquarters Allied Expeditionary Force—in the early morning hours of May 7. Eisenhower’s aides had attempted then to draft a suitably eloquent message to the Combined Chiefs reporting the official surrender. “I tried one myself,” Eisenhower’s chief of staff Walter Bedell Smith remembers, “and like all my associates, groped for resounding phrases as fitting accolades to the Great Crusade and indicative of our dedication to the great task just accomplished.”2305 The Supreme Commander listened quietly for a time, thanked everyone for trying and dictated his own unadorned report:

  The mission of this Allied force was fulfilled at 0241, local time, May 7th, 1945.2306

  Better to be brief, better than resounding phrases. Twenty million Soviet soldiers and civilians died of privation or in battle in the Second World War. Eight million British and Europeans died or were killed and another five million Germans. The Nazis murdered six million Jews in ghettos and concentration camps. Manmade death had ended thirty-nine million
human lives prematurely; for the second time in half a century Europe had become a charnel house.2307

  There remained the brutal conflict Japan had begun in the Pacific and refused despite her increasing destruction to end by unconditional surrender.

  Officially Byrnes was retired to South Carolina. In fact he was visiting Washington surreptitiously, absorbing detailed evening briefings by State Department division chiefs at his apartment at the Shoreham Hotel. On the afternoon of V-E Day he spent two hours closeted alone with Stimson. Then Harrison, Bundy and Groves joined them. “We all discussed the function of the proposed Interim Committee,” Stimson records.2308, 2309 “During the meeting it became very evident what a tremendous help Byrnes would be as a member of the committee.”

  The next morning the Interim Committee met for the first time in Stimson’s office. The gathering was preliminary, to fill in Byrnes, State’s Clayton and the Navy’s Bard on the basic facts, but Stimson made a point of introducing the former assistant President as Truman’s personal representative. The membership was thus put on notice that Byrnes enjoyed special status and that his words carried extra weight.

  The committee recognized that the scientists working on the atomic bomb might have useful advice to offer and created a Scientific Panel adjunct. Bush and Conant put their heads together and recommended Arthur Compton, Ernest Lawrence, Robert Oppenheimer and Enrico Fermi for appointment.

  Between the first and second meetings of the Interim Committee its Doppelgänger, the Target Committee, met again for two days, May 10 and 11, at Los Alamos. Added to the full committee as advisers were Oppenheimer, Parsons, Tolman and Norman Ramsey and for part of the deliberations Hans Bethe and Robert Brode. Oppenheimer took control by devising and presenting a thorough agenda:

  A. Height of Detonation2310

  B. Report on Weather and Operations

  C. Gadget Jettisoning and Landing

  D. Status of Targets

  E. Psychological Factors in Target Selection

  F. Use Against Military Objectives

  G. Radiological Effects

  H. Coordinated Air Operations

  I. Rehearsals

  J. Operating Requirements for Safety of Airplanes

  K. Coordination with 21st [Bomber Command] Program

  Detonation height determined how large an area would be damaged by blast and depended crucially on yield. A bomb detonated too high would expend its energy blasting thin air; a bomb detonated too low would expend its energy excavating a crater. It was better to be low than high, the committee minutes explain: “The bomb can be detonated as much as 40% below the optimum with a reduction of 24% in area of damage whereas a detonation [only] 14% above the optimum will cause the same loss in area.” The discussion demonstrates how uncertain Los Alamos still was of bomb yield. Bethe estimated a yield range for Little Boy of 5,000 to 15,000 tons TNT equivalent. Fat Man, the implosion bomb, was anybody’s guess: 700, 2,000, 5,000 tons? “With the present information the fuse would be set at 2,000 tons equivalent but fusing for the other values should be available at the time of final delivery. . . . Trinity data will be used for this gadget.”

  The scientists reported and the committee agreed that in an emergency a B-29 in good condition could return to base with a bomb. “It should make a normal landing with the greatest possible care. . . . The chances of [a] crash initiating a high order [i.e., nuclear] explosion are . . . sufficiently small [as to be] a justifiable risk.” Fat Man could even survive jettisoning into shallow water. Little Boy was less forgiving. Since the gun bomb contained more than two critical masses of U235, seawater leaking into its casing could moderate stray neutrons sufficiently to initiate a destructive slow-neutron chain reaction. The alternative, jettisoning Little Boy onto land, might loose the U235 bullet down the barrel into the target core and set off a nuclear explosion. For temperamental Little Boy, the minutes note, unluckily for the aircrew, “the best emergency procedure that has so far been proposed is . . . the removal of the gun powder from the gun and the execution of a crash landing.”

  Target selection had advanced. The committee had refined its qualifications to three: “important targets in a large urban area of more than three miles diameter” that were “capable of being damaged effectively by blast” and were “likely to be unattacked by next August.” The Air Force had agreed to reserve five such targets for atomic bombing. These included:

  (1) Kyoto—This target is an urban industrial area with a population of 1,000,000. It is the former capital of Japan and many people and industries are now being moved there as other areas are being destroyed. From the psychological point of view there is the advantage that Kyoto is an intellectual center for Japan and the people there are more apt to appreciate the significance of such a weapon as the gadget. . . .

  (2) Hiroshima—This is an important army depot and port of embarkation in the middle of an urban industrial area. It is a good radar target and it is such a size that a large part of the city could be extensively damaged. There are adjacent hills which are likely to produce a focusing effect which would considerably increase the blast damage. Due to rivers it is not a good incendiary target.

  The other three targets proposed were Yokohama, Kokura Arsenal and Niigata. An unsung enthusiast on the committee suggested a spectacular sixth target for consideration, but wiser heads prevailed: “The possibility of bombing the Emperor’s palace was discussed. It was agreed that we should not recommend it but that any action for this bombing should come from authorities on military policy.”

  So the Target Committee sitting in Oppenheimer’s office at Los Alamos under the modified Lincoln quotation that Oppenheimer had posted on the wall—THIS WORLD CANNOT ENDURE HALF SLAVE AND HALF FREE—remanded four targets to further study: Kyoto, Hiroshima, Yokohama and Kokura Arsenal.

  The committee and its Los Alamos consultants were not unmindful of the radiation effects of the atomic bomb—its most significant difference in effect from conventional high explosives—but worried more about radiation danger to American aircrews than to the Japanese. “Dr. Oppenheimer presented a memo he had prepared on the radiological effect of the gadget. . . . The basic recommendations of this memo are (1) for radiological reasons no aircraft should be closer than 2½ miles to the point of detonation (for blast reasons the distance should be greater) and (2) aircraft must avoid the cloud of radio-active materials.”

  Since the expected yields of the bombs under discussion made them something less than city-busters, the Target Committee considered following Little Boy and Fat Man with conventional incendiary raids. Radioactive clouds that might endanger LeMay’s follow-up crews worried the targeters, though they thought an incendiary raid delayed one day after an atomic bombing might be safe and “quite effective.”

  With a better sense for having visited Los Alamos of the weapons it was targeting, the Target Committee scheduled its next meeting for May 28 at the Pentagon.

  Vannevar Bush thought the second Interim Committee meeting on May 14 produced “very frank discussions.” The group, he decided, was “an excellent one.”2311 These judgments he passed along to Conant, who had been unable to attend. Stimson won approval of the Scientific Panel as constituted and discussed the possibility of assembling a similar group of industrialists. As his agenda noted, such a group would “advise of [the] likelihood of other nations repeating what our industry has done”—that is, whether other nations could build the vast, innovative industrial plant necessary to produce atomic bombs.2312

  That May Monday morning the committee received copies of Bush’s and Conant’s September 30, 1944, memorandum to Stimson, the discussion framed on Bohr’s ideas of the free exchange of scientific information and inspection not only of laboratories throughout the world but also of military installations. Bush promptly hedged his commitment to so open a world:

  I . . . said that while we made the memorandum very explicit, that it certainly did not indicate that we were irrevocably committed to any definite line of
action but rather felt that we ought to express our ideas early in order that there might be discussion as [a] result of which we might indeed change our thoughts as we studied into the subject further, and I said also that we would undoubtedly write the memorandum a little differently today due to the lapse of time since last September.2313

  At the end of the meeting Byrnes took his copy along and studied it with interest.2314

  The Secretary of State-designate was learning fast. When the Interim Committee met again on Friday, May 18, with Groves sitting in, Byrnes brought up the Bush-Conant memorandum as soon as draft press releases announcing the dropping of the first atomic bomb on Japan had been reviewed. It was Bush’s turn to be absent; Conant passed along the news:

  Mr. Byrnes spent considerable time discussing our memorandum of last fall, which he had read carefully and with which he was much impressed. It apparently stimulated his thinking (which was all that we had originally desired I imagine). He was particularly impressed with our statement that the Russians might catch up in three to four years. This premise was violently opposed by the General [i.e., Groves], who felt that twenty years was a much better figure. . . . The General is basing his long estimate on a very poor view of Russian ability, which I think is a highly unsafe assumption. . . .

  There was some discussion about the implications of a time interval as short as four years and various international problems were discussed, particularly the question of whether or not the President should tell the Russians of the existence of the weapon after the July test.

  Bohr’s proposal to enlist the Soviet Union in discussions before the atomic bomb became a reality here slips to the question of whether or not to tell the Soviets the bare facts after the first bomb had been tested but before the second was dropped on Japan. Byrnes thought the answer to that question might depend on how quickly the USSR could duplicate the American accomplishment. The Interim Committee’s recording secretary, 2nd Lieutenant R. Gordon Arneson, remembered after the war of this confrontation that “Mr. Byrnes felt that this point was a very important one.”2315 The veteran of House and Senate cloakrooms was at least as concerned as Henry Stimson to extract a quid pro quo for any exchange of information, as Conant’s next comment to Bush demonstrates: