* * *
As the plans for the June 1944 invasion of France began to take shape, another serious threat emerged: the possibility that the Germans might try to disrupt the Normandy landings by laying down a radioactive barrier along the beaches and approach routes, rendering them unsafe. If the Germans used ordinary explosive bombs containing radioactive material, and the Allied forces were unable to neutralize the contaminated area quickly, it could expose a large number of their troops, as well as civilians, to excessive radiation.
Groves worried that such a terrifying attack would have “disastrous results,” quite apart from the possibility it could trigger a major panic across the Allied countries. As D-day drew nearer, however, he was no closer to reaching a decision about what to do about the problem, and all the conflicting advice he had been given left him no better off than when he started. “This was a time I was most appreciative of Conant’s sound counsel,” he recalled, noting that the calm, deliberate Yankee was “never one to become unduly excited over the wild conjectures that the fertile minds of some of our people could produce, almost faster, it seemed, than we could disprove them.”
Groves and Marshall asked Conant to head a special S-1 committee to assess the danger and develop countermeasures should the Germans engage in radiological warfare. In May 1943, Conant recruited Arthur Compton and Harold Urey to assist him, and together they conducted an intensive study of the use of radioactive materials as an offensive military weapon. In July, Conant submitted a preliminary report: “It now seems extremely probable that it will be possible to produce by means of a self-sustaining pile large quantities of radioactive materials with varying half-lives in the order of magnitude of twenty days.” A week’s output, he thought, distributed over two square miles, could incapacitate much of the population and necessitate evacuation. Compton was so frightened by the specter of a radiological attack that he urged that “we should be ready to ‘reply in kind’ . . . before Christmas if this is considered military strategy.”
When Oppenheimer heard about Conant’s inquiry, he told Groves that he and Fermi had already been working on an idea to poison German foodstuffs, probably a reference to beta-strontium, a highly toxic radioactive by-product of fission. He then wrote Fermi that he had received approval to talk to Conant about “the application that seemed to us so promising,” but added with chilling pragmatism that it would not make sense to pursue it further “unless we can poison food sufficient to kill half a million men.” Oppenheimer pursued the plan with Teller, but eventually the scheme ran into too many problems, and there is no mention of it in Conant’s final report.
While he and his fellow committee members ultimately concluded the danger of a radiological attack was low—Conant, in contrast with the others, considered it “extremely unlikely”—they still recommended taking some precautionary measures to minimize its effects. Groves ordered these preparations as part of the highly secret Operation Peppermint, which provided for shipping portable Geiger counters to Britain, training officers in the use of detection equipment, and establishing channels for reporting any incidents promptly to avoid a panic. Army medical personnel in the European theater were instructed to report any symptoms of “unknown etiology.” Along with signal and air officers, they were also told to look out for the unexplained fogging or blackening of photographic or X-ray film, a telltale sign of radiation exposure.
Not wanting to unduly alarm General Dwight D. Eisenhower, the supreme commander of the Allied Expeditionary Force, Groves instructed his aide, Major Arthur V. Peterson, to acquaint him with the possibility the Germans could produce extremely effective contaminating agents, and could employ them without prior warning, but to tread softly and “emphasize our belief that they would not be used and the invasion plans should be made accordingly.”
Groves’s confidence in Conant’s “sound counsel” is breathtaking. What if he was wrong? In the course of developing plutonium, the Germans were bound to have discovered the hazardous by-products produced by their reactors and to consider using them as a weapon to combat an invading army. Conant’s opinion that they would not deploy these unreliable munitions was, at best, an educated guess, based on his analysis of the practical obstacles involved in handling radioactive material, and uniformly dispersing it over a designated area. But there were many possible forms of distribution, including spraying a persistent poison from low-flying planes or setting it off in land mines, which could also render streets, airfields, and rail yards uninhabitable. Operation Peppermint was concerned primarily with detection; the actual defensive measures were minimal.
Groves, of course, checked with Bush, who as usual sized up the situation much the same way Conant did. He had initially worried that radioactive contaminants or nerve agents might be used in combination with long-range rockets or V-1s—aerial photographs of the French coast had revealed large installations that looked like launch sites—but wrote Groves that he had come to the conclusion that it was too difficult and would not be an effective method. (Bush and Conant similarly believed it unlikely the Germans would initiate a gas attack, given the Allies had achieved air superiority, though a sixty-day supply of chemical bombs was sent to depots in England in case retaliatory operations had to be mounted.) Still, Eisenhower had to be informed. Bush, who traveled to England to brief him in person, had the unenviable task of explaining that while they had more or less ruled out the possibility of a toxic payload on Omaha Beach, there was still a good chance missiles might rain down on Plymouth and Bristol, the main staging areas for the invasion. “You scare the hell out of me,” Eisenhower said to Bush when he was done, no doubt realizing it was his men who would pay the price if it turned out the scientists did not know their stuff.
On May 11, 1944, Eisenhower wrote Groves that he had carefully reviewed the situation, but since the Combined Chiefs of Staff had not officially brought it to his notice, he was assuming “on the present available intelligence, the enemy will not implement this project.” Owing to the importance of maintaining secrecy “to avoid a possible scare,” he had passed on the information to a very limited number of people, and no US or British commander participating in Overlord had been told. Moreover, he had not taken enough precautionary steps to “adequately counter enemy action of this nature.”
When Groves read Eisenhower’s letter, it must have given him a moment’s pause. “I knew our advice had been fully accepted,” he recalled in his memoir, “and that nothing more could be done except to pray that we had not made a mistake.” Groves had assumed enormous responsibility in connection with the invasion, neglecting to inform the Combined Chiefs of Staff or US Joint Chiefs of Staff of the threat. It gave him, Conant, and the handful who knew about it “some bad hours” until they learned the Allied troops had made good their landing without encountering any radioactive interference.
Bush and Stimson were in a car headed for Capitol Hill when the first V-1 rocket was fired at London on June 13, in retaliation for the successful D-day landings the week before. After they had listened to the news on the radio, a dramatic report about the new kind of German flying bomb that had killed eight civilians and left a crater on a London street, Stimson put his hand on Bush’s knee and asked, “Well, Van, how do you feel now?” But they were both thinking the same thing: the payload of the vengeance bomb had been a conventional explosive. No radiological products. No poison gas. “Very much relieved,” was all Bush said.
* * *
The pressure did not let up that spring. At the same time he was trying to deal with the potential threat of radiological weapons on Allied territory and troops overseas, Conant had to cope with a series of discouraging setbacks on his own end. The plutonium manufactured in Oak Ridge, which finally began to reach Los Alamos in tangible quantities in early 1944, revealed for the first time an isotope with undesirable nuclear properties: plutonium-240, a strong spontaneous fissioner. Their problems reached a peak when Emilio Segrè’s tests on plutonium confirmed their worst fears
: it was not pure enough. The plutonium would fizzle out in a predetonation. Despite all their efforts and the development of the high-velocity cannon, plutonium would not work in the gun-type bomb. Oppenheimer broke the bad news to Conant on July 11. The bomb they had dubbed the Thin Man would never work. The disappointment in the room was palpable. It meant that all the plutonium coming from the giant pile at Hanford would not be reliable enough to use. The possibility of developing a plutonium weapon to defeat the Germans now seemed slim.
During a series of urgent meetings in Chicago on July 17, Conant consulted with Oppenheimer and Charles Thomas, who had come from Los Alamos, and then conferred with Groves and Fermi in an evening meeting. They reached an inescapable conclusion: the gun method for plutonium had to be scratched, eliminating the hoped-for shortcut to the bomb. Plutonium was useless unless an alternative design for a weapon could be found within a few months. The gloomy prognosis was reflected in the epitaph Conant scrawled across the top of Thomas’s upbeat June 13 status report: “All to no avail, alas!”
Fortunately, there was an alternative, but it was far from finished. A small group at the laboratory had continued work on Neddermeyer’s complicated implosion design and believed it could be achieved. When Conant talked to Oppenheimer, however, the latter was not optimistic about their chances of developing it quickly. The implosion program was floundering. Neddermeyer was systematic and difficult to work with and was continually in conflict with Parsons, who had doubted him from the beginning. As a navy ordnance officer, Parsons had his own set ideas about how things should be done. Kistiakowsky, a brilliant improviser, was caught in the middle and was so unhappy that he had asked to be released from the project. “The situation is a mess,” Kisty had written after his first visit to Los Alamos. There was “a serious lack of mutual confidence between Parsons and Neddermeyer,” and it was doubtful the former “believes in its success.” Furthermore, Teller, who had been appointed head of a small implosion theory group, had lost interest in the task. He did not like working under Bethe and instead insisted on spending all his time on “the Super,” the hydrogen weapon, which few believed would be developed in time to affect the war. Oppenheimer allowed Teller to go his own way, but a sign of his growing impatience was a little prayer he would sometimes mutter under his breath: “May the Lord preserve us from the enemy without and the Hungarians within.”
By the time Conant returned to Los Alamos in July, he felt “the situation was desperate.” The personality conflicts and turf battles—between “the most colossal egos” he’d ever encountered, he confided to Kisty—were dragging down the experimental effort at the very moment it had to be prosecuted vigorously. They had to make implosion work if there was to be any hope of developing an effective plutonium bomb. To step up the effort and avoid further disputes, the whole implosion operation would need to be completely overhauled and expanded.
Hoping for a fresh perspective, Conant and Oppenheimer went for a long hike in the mountains and began formulating a new plan of attack. Parsons would continue to head the Ordnance Division, but Kistiakowsky was put in charge of the new X (Explosives) Division dedicated to the difficult high-explosives development work, studying implosion dynamics and generally trying to figure out how to make the weapon do what they wanted it to. Robert Bacher was asked to run the G (Gadget) Division to investigate implosion experimentally and design the geometric sphere. Exercising great tact under the circumstances, Oppenheimer solved the management problem by easing Neddermeyer into the role of senior technical advisor, thereby improving the attitude and effectiveness of the entire unit. Morale received a much-needed boost when Fermi agreed to come in September and stay for the duration.
The injection of new blood—in the form of mathematician John von Neumann, physicist Luis Alvarez, fresh from the radar lab, and Commander Norris E. Bradbury, a Stanford University physicist with four years’ experience at the Dahlgren Naval Proving Ground—helped them overcome some stubborn problems and move on. The development of “explosive lenses,” suggested by James Tuck, a member of the British Technical Mission, and based on specially shaped charges designed to crack armor, finally generated the powerful series of shock waves necessary for successful implosion. The new method required exhaustive experimentation. Groves brought in reinforcements: six hundred young technicians, or SEDs (members of the US Army’s Special Engineering Detachment), to help with the high-explosives development work and bomb construction.
As the laboratory girded itself for the final push, all the other divisions were reorganized and refocused on the fast-approaching deadlines. The Manhattan Project was continuing to expand and now cost $100 million a month. Results were essential. Everyone worked at a frenzied pace. The implosion experiments were ambitious, and with so much riding on them, Oppenheimer leaned heavily on Conant as they entered the home stretch, asking him to come to Los Alamos with greater frequency to help see the work through to the end. Conant’s broad understanding and common sense would help keep them on track to the very last step and mediate any conflicting viewpoints that might threaten to disrupt their progress. “Your confidence in our future success is something that I would like to have checked against realities just as often as possible,” Oppie confided, and, in a more heartfelt note, added, “I think the next months will inevitably be a time when we shall value your advice and help to a very special degree.”
As the momentum of the work intensified, Conant could see the toll the pressure and anxiety were taking on Oppenheimer. He had shrunk to 113 pounds and was so painfully thin his shoulder blades poked through his shirt. To keep up his spirits, Conant sent letters of encouragement and sober, pedagogical words of praise: “Just a line to tell you once again how satisfactory I think everything is going at Y,” he wrote after seeing how the personnel changes had revitalized the implosion program. “In all seriousness, you are to be congratulated on the progress made and the organization as it now stands.”
Conant advised Groves that Los Alamos should proceed with plans for the uranium gun-assembly bomb (Little Boy) and two kinds of implosion bombs (Fat Man), the first using uranium-235, and, as soon as they had it perfected, the second using plutonium. The implosion bombs would be low efficiency—Conant judged the blast would be the equivalent of only a few hundred tons of TNT, but at least they were a way of utilizing the atomic material they had produced at great expense.
On August 7, 1944, Groves presented Army Chief of Staff General Marshall with a new weapons timetable: several implosion bombs would be available between March and the end of June 1945, with a good chance for improved power. But if the development of the implosion bomb did not fulfill “present expectations,” they still had the gun-type bomb as a fallback. The Little Boy bomb was essentially completed—although they did not have enough U-235 to arm it—and he could state with assurance that it would be ready by August 1, 1945. The only problem was that since the gun assembly required large amounts of U-235, it would be possible to deliver only one, or at most two, additional bombs in 1945. They estimated its destructive effect would be roughly twice that expected of the low-powered implosion bomb. There was no longer any doubt that they would have weapons available for use; the only question was how efficiently the first models would work. While Groves’s report was careful to point out that this schedule was based on “reasonable success with experiments yet to be conducted,” he and his science advisors rather glossed over the fact that they had no idea when the plants would produce sufficient quantities of U-235 and plutonium for a weapon.
Either way, the revised timetable meant that in all probability, the atomic bomb would arrive too late for the German war. The summer of 1944 held out the promise of victory in Europe. On June 6, more than 150,000 Allied troops landed on the Normandy beaches, and, after weeks of bloody and relentless fighting, succeeded in gaining firm control of the peninsula. By the end of July, American soldiers had smashed through the enemy’s defenses and won the costly battle for Saint-Lô, France. The Ge
rman front was crumbling. On August 1 General George Patton’s Third Army, which led the surge in northern France, began fanning out across the open country, racing for Paris. As terrible as the Allied losses had been, the Germans fared far worse, repeating a pattern that was becoming standard and giving the final outcome the feel of mathematical inevitability. Europe would be won by conventional means. It looked increasingly likely that if a bomb were ready—and if it were used—Japan would be its intended target.
* * *
Now that the tide was turning against the aggressors, it was no longer possible to delay decisions about the postwar world. Conant had been consumed with the bomb project, and it had been a good many months since he had made one of the belligerent speeches—demanding Germany’s unconditional surrender, no stalemate, no negotiated peace—he had been known for in the early days of the war. But over the spring and summer of 1944, he found himself worrying that Americans were too optimistic about the future; too confident that international cooperation would be sufficient to prevent World War III. He did not share Time publisher Henry Luce’s belief that at the war’s end, the United States would automatically assume “leadership of the world,” and inaugurate “the American Century.” Stalin had made it clear at the December 1943 summit with FDR and Churchill in Tehran, Iran, and in his subsequent actions, that he would not be denied dominant influence in Eastern Europe. The Russian leader intended to play the part of world bully, extending his reach to the Baltic states and Italy, and ensuring that Poland never again fell into anti-Soviet hands.
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