Making of the Atomic Bomb

by Richard Rhodes

  Hull considered these difficulties while Byrnes sailed the Atlantic and sent along a cable of further advice on July 16. The Japanese might reject a challenge to surrender, the former Secretary of State argued, even if it allowed the Emperor to remain on the throne. In that case not only would the militarists among them be encouraged by what they would take to be a sign of weakening Allied will, but also “terrible political repercussions would follow in the U.S. . . . Would it be well first to await the climax of Allied bombing and Russia’s entry into the war?”2492

  The point of warning the Japanese was to encourage an early surrender in the hope of avoiding a bloody invasion; the trouble with waiting until the Soviet Union entered the war was that it left Truman where he had dangled uncomfortably for months: over Stalin’s barrel, dependent on the USSR for military intervention in Manchuria to tie up the Japanese armies there. Hull’s delaying tactic might improve the first prospect; but it might also secure the second.

  Another message arrived in Potsdam that evening, however, that changed the terms of the equation, a message for Stimson from George Harrison in Washington announcing the success of the Trinity shot:

  Operated on this morning. Diagnosis not yet complete but results seem satisfactory and already exceed expectations. Local press release necessary as interest extends great distance.2493 Dr. Groves pleased. He returns tomorrow. I will keep you posted.

  “Well,” Stimson remarked to Harvey Bundy with relief, “I have been responsible for spending two billions of dollars on this atomic venture. Now that it is successful I shall not be sent to prison in Fort Leavenworth.”2494 Happily the Secretary of War carried the cable to Truman and Byrnes, just returned to Potsdam from Berlin.

  In Stimson’s welcome news Byrnes saw a more general reprieve. It informed his overnight response to Hull. “The following day” Hull says, “I received a message from Secretary Byrnes agreeing that the statement [warning the Japanese] should be delayed and that, when it was issued, it should not contain this commitment with regard to the Emperor.”2495 Byrnes had good reason to delay a warning now: to await the readying of the first combat atomic bombs. Those weapons would answer Hull’s first objection; if the Japanese ignored a warning, then the United States could deliver a brutally retributive response. With such weapons in the U.S. arsenal unconditional surrender need not be compromised. And America no longer required the Soviet Union’s aid in the Pacific; the problem now would be not dealing the Soviets in but stalling to keep them out. “Neither the President nor I,” Byrnes affirms, “were anxious to have them enter the war after we had learned of this successful test.”2496

  Byrnes and others within the American delegation came to realize that preserving the Emperor might be sensible policy if Hirohito alone could persuade the far-flung Japanese armies, undefeated and with a year’s supply of ammunition on hand, to lay down their arms.2497 The new Secretary of State, who was drafting a suitable declaration, sought a formula that would not arouse the American people but might reassure the Japanese. The Joint Chiefs produced its first version: “Subject to suitable guarantees against further acts of aggression, the Japanese people will be free to choose their own form of government.”2498 The Japanese polity resided in the Imperial House, not in the people, but provision for popular government was as conditional an unconditional surrender as the enemy would be allowed.

  George Harrison cabled Stimson on July 21 that “all your local military advisors engaged in preparation definitely favor your pet city”: Groves still coveted Kyoto.2499 Stimson quickly returned that he was “aware of no factors to change my decision. On the contrary new factors here tend to confirm it.”2500

  Harrison also asked Stimson to alert him by July 25 “if [there is] any change in plans” because “[the] patient [is] progressing rapidly.”2501 At the same time Groves requested permission from George Marshall to brief Douglas MacArthur, who had not yet been told about the new weapon, in view of “the imminence of the use of the atomic fission bomb in operations against Japan, 5 to 10 August.”2502, 2503 The 509th had begun flying Pumpkin missions over Japan the previous day for combat experience and to accustom the enemy to small, unescorted flights of B-29’s at high altitude.

  Groves’ eyewitness narrative of the Trinity test had arrived that Saturday just before noon. Stimson sought out Truman and Byrnes and had the satisfaction of riveting them to their chairs by reading it aloud. Groves estimated “the energy generated to be in excess of the equivalent of 15,000 to 20,000 tons of TNT” and allowed his deputy, Thomas F. Farrell, to call the visual effects “unprecedented, magnificent, beautiful, stupendous and terrifying.” Kenneth Bainbridge’s “foul and awesome display” became at Farrell’s hand “that beauty the great poets dream about but describe most poorly and inadequately,” which Farrell presumably meant for a superlative. “As to the present war,” Farrell opined, “there was a feeling that no matter what else might happen, we now had the means to insure its speedy conclusion and save thousands of American lives.” Stimson saw that Truman was “tremendously pepped up” by the report. “[He] said it gave him an entirely new feeling of confidence.”2504

  The President met the next day to discuss Groves’ results with Byrnes, Stimson and the Joint Chiefs, including Marshall and Hap Arnold. Arnold had long maintained that conventional strategic bombing by itself could compel the Japanese to surrender. In late June, when invasion was being decided, he had rushed LeMay to Washington to work the numbers. LeMay figured he could complete the destruction of the Japanese war machine by October 1.2505 “In order to do this,” writes Arnold, “he had to take care of some 30 to 60 large and small cities.”2506 Between May and August LeMay took care of fifty-eight.2507 But Marshall disagreed with the Air Force assessment. The situation in the Pacific, he had told Truman in June, was “practically identical” to the situation in Europe after Normandy. “Airpower alone was not sufficient to put the Japanese out of the war.2508 It was unable alone to put the Germans out.” He explained his reasoning at Potsdam to an interviewer after the war:

  We regarded the matter of dropping the [atomic] bomb as exceedingly important.2509 We had just gone through a bitter experience at Okinawa [the last major island campaign, when the Americans lost more than 12,500 men killed and missing and the Japanese more than 100,000 killed in eighty-two days of fighting]. This had been preceded by a number of similar experiences in other Pacific islands, north of Australia. The Japanese had demonstrated in each case they would not surrender and they would fight to the death. . . . It was expected that resistance in Japan, with their home ties, would be even more severe. We had had the one hundred thousand people killed in Tokyo in one night of [conventional] bombs, and it had had seemingly no effect whatsoever. It destroyed the Japanese cities, yes, but their morale was not affected as far as we could tell, not at all. So it seemed quite necessary, if we could, to shock them into action. . . . We had to end the war; we had to save American lives.

  Before Groves’ report arrived, Dwight Eisenhower, a hard and pragmatic commander, had angered Stimson with a significantly different assessment. “We’d had a nice evening together at headquarters in Germany,” the Supreme Allied Commander remembers, “nice dinner, everything was fine. Then Stimson got this cable saying the bomb had been perfected and was ready to be dropped.”2510 The cable was the second Harrison had sent, the day after the Trinity test when Groves arrived back in Washington:

  Doctor has just returned most enthusiastic and confident that the little boy is as husky as his big brother. The light in his eyes discernible from here to Highhold and I could have heard his screams from here to my farm.2511

  Highhold was Stimson’s Long Island estate, 250 miles from Washington—the Trinity flash had been visible even farther from Zero than that. Harrison’s farm was 50 miles outside the capital. Eisenhower found the allegorical code less than amusing and the subject baleful:

  The cable was in code, you know the way they do it. “The lamb is born” or some damn thing li
ke that. So then he told me they were going to drop it on the Japanese. Well, I listened, and I didn’t volunteer anything because, after all, my war was over in Europe and it wasn’t up to me. But I was getting more and more depressed just thinking about it. Then he asked for my opinion, so I told him I was against it on two counts. First, the Japanese were ready to surrender and it wasn’t necessary to hit them with that awful thing. Second, I hated to see our country be the first to use such a weapon. Well . . . the old gentleman got furious. And I can see how he would. After all, it had been his responsibility to push for all the huge expenditure to develop the bomb, which of course he had a right to do, and was right to do. Still, it was an awful problem.2512

  Eisenhower also spoke to Truman, but the President concurred in Marshall’s judgment, having already formed his own. “Believe Japs will fold up before Russia comes in,” he confided to his diary almost as soon as he heard of the Trinity success. “I am sure they will when Manhattan appears over their homeland.”2513

  When to issue the Potsdam Declaration now became essentially a question of when the first atomic bombs would be ready to be dropped. Stimson queried Harrison, who responded on July 23:

  Operation may be possible any time from August 1 depending on state of preparation of patient and condition of atmosphere. From point of view of patient only, some chance August 1 to 3, good chance August 4 to 5 and barring unexpected relapse almost certain before August 10.2514

  Stimson had also asked for a target list, “always excluding the particular place against which I have decided. My decision has been confirmed by highest authority.”2515 Harrison complied: “Hiroshima, Kokura, Niigata in order of choice here.”2516

  Which meant that Nagasaki had not yet, as of the last full week in July, been added to the list. Within days it would be. Official Air Force historians speculate that LeMay’s staff proposed it.2517 The requirement for visual bombing was probably the reason. Hiroshima was 440 miles southwest of Niigata. Nagasaki, over the mountains from Kokura on Kyushu, was a further 220 miles southwest of Hiroshima. If one city was socked in, another might be clear. Nagasaki was certainly also added because it was one of the few major cities left in Japan that had not yet been burned out.

  A revealing third cable completed the day’s communications from Harrison (the metallurgists at Los Alamos had finished the Pu core for Fat Man that day). It concerned possible future deliveries of atomic bombs and hinted at a forthcoming change in design, probably to the so-called “mixed” implosion bomb with a core of U235 and plutonium alloyed together. Such a core could draw on the resources of both Oak Ridge and Hanford:

  First one of tested type [i.e., Fat Man] should be ready at Pacific base about 6 August. Second one ready about 24 August. Additional ones ready at accelerating rate from possibly three in September to we hope seven or more in December. The increased rate above three per month entails changes in design which Groves believes thoroughly sound.2518

  Stimson reported Harrison’s several estimates to Truman on Tuesday morning, July 24. The President was pleased and said he would use them to time the release of the Potsdam Declaration. The Secretary took advantage of the moment to appeal to Truman to consider assuring the Japanese privately that they could keep their Emperor if they persisted in making that concession a condition of surrender. Deliberately noncommittal, the President said he had the point in mind and would take care of it.

  Stimson left and Byrnes joined Truman for lunch. They discussed how to tell Stalin as little as possible about the atomic bomb. Truman wanted protective cover when Stalin learned that his wartime allies had developed an epochal new weapon behind his back but wanted to give as little as possible away. Byrnes also devised a more immediate reason for circumspection, he told the historian Herbert Feis in 1958:

  As a result of his experience with the Russians during the first week of the Conference he had come to the conclusion that it would be regrettable if the Soviet Union entered the [Pacific] war, and . . . he was afraid that if Stalin were made fully aware of the power of the new weapon, he might order the Soviet Army to plunge forward at once.2519

  But in fact Stalin already knew about the Trinity test.2520 His agents in the United States had reported it to him. It appears he was not immediately impressed. There is gallows humor in Truman’s elaborately offhand approach to the Soviet Premier at the end of that day’s plenary session at the Cecilienhof Palace, stripped and shabby, where pale German mosquitoes homing through unscreened windows dined on the sanguinary conquerors. Truman left behind his translator, rounded the baize-covered conference table and sidled up to his Soviet counterpart, both men dissimulating. “I casually mentioned to Stalin that we had a new weapon of unusual destructive force. The Russian Premier showed no special interest. All he said was that he was glad to hear it and hoped we would make ‘good use of it against the Japanese.’ ”2521 “That,” concludes Robert Oppenheimer dryly, knowing how much at that moment the world lost, “was carrying casualness rather far.”2522

  If Stalin was not yet impressed with the potential of the bomb, Truman in his private diary was waxing apocalyptic, biblical visions mingling in his autodidact’s mind with doubt that the atom could be decomposed and denial that the new weapon would be used to slaughter civilians:

  We have discovered the most terrible bomb in the history of the world.2523 It may be the fire destruction prophesied in the Euphrates Valley Era, after Noah and his fabulous Ark.

  Anyway we “think” we have found a way to cause a disintegration of the atom. An experiment in the New Mexican desert was startling—to put it mildly. . . .

  This weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop this terrible bomb on the old Capital or the new.

  He & I are in accord. The target will be a purely military one and we will issue a warning statement asking the Japs to surrender and save lives. I’m sure they will not do that, but we will have given them the chance. It is certainly a good thing for the world that Hitler’s crowd or Stalin’s did not discover this atomic bomb. It seems to be the most terrible thing ever discovered, but it can be made the most useful.

  The Tuesday Truman mentioned the new weapon to Stalin the Combined Chiefs met with their Soviet counterparts; Red Army chief of staff General Alexei E. Antonov announced that Soviet troops were assembling on the Manchurian border and would be ready to attack in the second half of August. Stalin had said August 15 before. Byrnes was anxious that the Soviets might prove uncharacteristically punctual.

  That afternoon in Washington Groves drafted the historic directive releasing the atomic bomb to use.2524 It passed up through Harrison for transmission by radio EYES ONLY to Marshall “in order that your approval and the Secretary of War’s approval might be obtained as soon as possible.”2525 (A small map of Japan cut from a large National Geographic Society map and a one-page description of the chosen targets, which now included Nagasaki, followed by courier.) Marshall and Stimson approved the directive at Potsdam and presumably showed it to Truman, though it does not record his formal authorization; it went out the next morning to the new commander of the Strategic Air Force in the Pacific:

  To General Carl Spaatz, CG, USASTAF:

  1. The 509 Composite Group, 20th Air Force will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki. . . .

  2. Additional bombs will be delivered on the above targets as soon as made ready by the project staff. . . .

  3. Dissemination of any and all information concerning the use of the weapon against Japan is reserved to the Secretary of War and the President of the United States. . . .

  4. The foregoing directive is issued to you by di
rection and with the approval of the Secretary of War and of the Chief of Staff, USA.

  As Groves drafted the directive the metallurgists at Los Alamos finished casting the rings of U235 that fitted together to form the gun bomb’s target assembly, the last components needed to complete Little Boy.

  Strategy and delivery intersected on July 26 and synchronized. The Indianapolis arrived at Tinian. Three Air Transport Command C-54 cargo planes departed Kirtland Air Force Base with the three separate pieces of the Little Boy target assembly; two more ATC C-54’s departed with Fat Man’s initiator and plutonium core.2526 Meanwhile Truman’s staff released the Potsdam Declaration to the press at 7 P.M.2527 for dispatch from Occupied Germany at 9:20. It offered on behalf of the President of the United States, the President of Nationalist China and the Prime Minister of Great Britain to give Japan “an opportunity to end this war”:

  Following are our terms. We will not deviate from them. There are no alternatives. We shall brook no delay.

  There must be eliminated for all time the authority and influence of those who have deceived and misled the people of Japan into embarking on world conquest . . . .

  Until such a new order is established . . . points in Japanese territory . . . shall be occupied.

  . . . Japanese sovereignty shall be limited to the islands of Honshu, Hokkaido, Kyushu, Shikoku and such minor islands as we determine.

  The Japanese military forces, after being completely disarmed, shall be permitted to return to their homes with the opportunity to lead peaceful and productive lives.

  We do not intend that the Japanese shall be enslaved as a race or destroyed as a nation, but stern justice shall be meted out to all war criminals. . . . Freedom of speech, of religion, and of thought, as well as respect for the fundamental human rights shall be established.