Man of the Hour

by Jennet Conant

  The Review Committee gave the Los Alamos research program the thumbs-up on May 10. After going over their report, Conant and Groves decided that the investigation of the theoretical aspects of the “superbomb” should continue—its potential was too great to overlook—but the atomic bomb, as the practical military weapon, had priority. They also concurred that chemistry/metallurgy and ordnance were the least developed and needed to be pushed. Kennedy’s division was ordered to take over the purification process for plutonium—by which it was transformed into a metal and refined to a high level of purity to ensure it would reach critical mass and not melt down—an arduous, multistage task that would require additional facilities as well as a large force of chemists, analysts, and assistants. Then Parsons announced that he would need his own laboratory and ballistics range, along with a team of two hundred ordnance experts. These changes effectively doubled the size of Los Alamos. They were just the first in a series of expansions that added greatly to Conant’s indigestion in the months to come.

  By his November 1943 visit, several crucial questions had been answered. Compton had made good on his promise to master the process for separating plutonium from the contents of the pile. In July Glenn Seaborg delivered the first microscopic speck of plutonium, detectable only by its radioactivity, which he brought to Los Alamos from Chicago in his suitcase. From only traces of the new element, they were able to conduct the first nuclear experiments that established that not only did plutonium emit neutrons on fusion, but also the number was greater than in uranium. Finally, here was proof of plutonium’s “intrinsic explosibility.” They all breathed a huge sigh of relief. Conant and Groves were especially thankful because it justified the massive $350 million plutonium pile already under construction at Hanford, Washington. Because of the need to optimize every approach, they had rushed ahead on the expensive reactor without waiting for the studies to be completed. The go-ahead signal had been given on scant evidence, and Conant had sweated the huge sums riding on what amounted to Compton and company’s confident bet.

  That fall, Conant received another piece of news that added to his peace of mind. Robert Wilson, a young Lawrence protégé who had secured the use of Harvard’s cyclotron for Los Alamos and now headed up the cyclotron group, confirmed that most of the neutrons emitted from fissioning U-235 were “fast” neutrons, generated in less than one billionth of a second. This was evidence that the neutrons were being transformed at an unbelievable speed. It provided ample margin for an efficient explosive reaction. Success of the gun-assembly weapon was now a near certainty.

  With the basic physics out of the way, they could get on with the nuts-and-bolts work of designing the bomb itself. Parsons immediately set to work on a plutonium gun. Tests on the small amounts of plutonium available had shown that it had a much higher rate of spontaneous fission than uranium; consequently, they would need a much faster gun, or there was a chance it might predetonate, reducing the bomb’s efficiency. They needed to develop a miniature, high-velocity cannon that could fire the subcritical projectile mass into the target sphere fast enough to keep the weapon from fizzling out, but at the same time was small enough to fit into a bomb casing—which in turn had to fit into the belly of a B-29 bomber. To achieve a more compact mechanism with greater muzzle velocity, they could try welding two guns together. Once the designers got the plutonium gun to perform, the uranium model would be comparatively simple. Taking over one of the old homesteads, called Anchor Ranch, Parsons and his team began an elaborate testing program to perfect the gun requirements. Since these were not your run-of-the-mill howitzers, and no military arsenal made anything that suited their purposes, he got the Naval Gun Factory in Washington, DC, to fabricate them from strong high-alloy steel.

  While they waited for the guns, the alternative way to detonate plutonium suggested earlier by Seth Neddermeyer suddenly took on a new importance. The Hungarian mathematician Johnny von Neumann, who happened to be visiting Los Alamos that autumn, was convinced that not only could implosion be made into a precision weapon, but also that the higher implosion velocities would eliminate any concerns about predetonation. After going over the research with his fellow Hungarian Edward Teller, von Neumann suggested that this method of compression might also require less plutonium. If there was any chance that a bomb might be ready earlier and require less active material, Conant and Groves could not afford to pass it up. Conant knew there was only one man capable of leading the experimental effort into the complex implosion technique: George Kistiakowsky, chief of the NDRC’s explosives division. Kistiakowsky had resisted Oppenheimer’s pleas to join the Los Alamos lab full-time because he wanted to work only on weapons that would make a difference in the current war. But in the end, he allowed Conant, whose opinion was the only one that “really mattered,” to persuade him to move to the mesa.

  Parsons, free from the burden of nuclear research, began preparations for the combat use of the bomb. He assembled another ordnance team, headed by Norman Ramsey, one of Rabi’s talented radar crew, and began making arrangements for full-scale drop tests of two basic bomb models with a modified B-29 at Muroc Army Air Base in California. The tests would allow them to obtain valuable ballistic data and determine the best procedures for dropping the bomb. For security reasons, Ramsey called the test dummies the “Thin Man” for the gun assembly, and the “Fat Man” for the implosion weapon. In his report, he noted that during their phone conversations the army air forces officers tried to make it sound as though they were “modifying a plane to carry Roosevelt (the Thin Man) and Churchill (the Fat Man).”

  CHAPTER 16

  * * *

  One Fell Stroke

  The essence of war is not slaughter but impressing your will upon the enemy.

  —JBC to Vannevar Bush

  As the Anglo-American high command perfected its plans for the invasion of Europe, Conant continued to face the very real possibility that the Germans would produce an atomic bomb before the Allies could. For all his expressions of optimism, he had far too much respect for Werner Heisenberg and the physicists at the Kaiser-Wilhelm Institute to count them out for a moment. Until he had proof to the contrary, he had to assume the Nazis were working on their nuclear program with the same feverish intensity as the Manhattan Project scientists.

  What kept him awake at night was how little was known about Germany’s progress toward a nuclear weapon. If nothing else, it made it impossible to estimate realistically how much time they had left to complete their own project. Their ignorance was a thorn in Conant’s side that kept him unsettled and constantly on edge. He took some comfort in the idea that the enemy must be encountering the same baffling problems, observing in a private memorandum that “at least every difficulty that develops means probably an equal difficulty for the Germans!” His main concern was that the Nazis would stumble on to simple solutions to puzzles that Los Alamos was still struggling with; solutions that would propel them over the finish line first.

  For months, the Reich had harped on its plan to use a secret scientific weapon in retaliation for Allied air attacks. On December 3, 1943, a Berlin radio broadcast declared that Germany would end the war “by one fell, drastic stroke,” adding, “Mankind is not far from the point where it can blow up half the globe.” Some of the refugee scientists at the Met Lab and Los Alamos were convinced the Germans were preparing to use atomic bombs against the United States or, more likely, England. One even urged Groves to make an official broadcast warning the American people of the danger of a nuclear attack—a possibility the general considered sufficiently remote that he rejected doing any such thing. “Although this was sometimes hard on our nerves,” Groves acknowledged later, “it did keep us from ever becoming overconfident.”

  When the Manhattan Project assumed responsibility for all atomic intelligence in the fall of 1943, Conant and Groves agreed that their first priority must be to remain as informed as possible on the danger posed by German science. It was absolutely essential that they kn
ow what the other side might be capable of if their backs were to the wall. The steady stream of rumors from behind enemy lines stoked everyone’s fears and suspicions but provided few details about the status of the German atomic program. (The Japanese did not concern them, not because they doubted their technical competence but because it would be too great an undertaking for their industry.) Early in the war, evidence of Germany’s interest in making a bomb had surfaced when the Nazis occupied Norway in 1940 and seized the Norsk Hydro plant at Rjukan near Vemork, about sixty miles west of Oslo. The Germans turned the complex into a heavy water operation, and by September 1942, it was estimated that they were shipping 120 kilograms of the enriched water back to Berlin each month for experimental use. If they were able to stockpile enough heavy water, Germany could conceivably produce the plutonium it needed for an atomic bomb.

  At the time, Conant and Bush recommended that Rjukan be bombed, but the British rejected the idea because they already had a secret sabotage operation in the works. Unaware of this, Conant persisted, and on December 9, 1942, he wrote Groves that the presumed German head start of a year or even eighteen months persuaded him that “every effort should be made by MID [Military Intelligence Division], ONI [Office of Naval Intelligence] and OSS, as well as the British Intelligence service, to obtain clues as to the German progress and their plans, with the view . . . to bombing the plants and laboratories where such work is in progress,” emphasizing that they should “strain every nerve on the countermeasure side, which includes espionage and bombing.”

  The British struck first, with their Special Operations Executive (SOE) launching an extremely risky assault mission to destroy the Norsk Hydro heavy water plant on October 12, 1942. Bad weather doomed the already dangerous assignment: the two gliders transporting the British paratroopers crashed en route, killing many of the occupants and injuring the rest. The survivors were all captured by the Germans and executed. The attack was an unmitigated disaster, ending with a total of thirty-eight dead and alerting Nazi officials to the Allies’ keen interest in heavy water. Determined to take out the plant, the British carried out an even more daring assault on February 17, 1943, with a nine-man team cross-country skiing into the site, scaling the icy ravine, and blowing up the heavy water electrolysis chambers. Although the British deemed the operation a success, the Germans repaired the damage with surprising speed and reactivated the plant.

  The British operation, which Conant and Groves learned about by reading news dispatches from Oslo, caused them “some headaches,” the general recalled, clearly aggrieved. One Swedish newspaper reported the successful sabotage and then went on to speculate about the importance of heavy water in attempts to break down the atom. The story was picked up by the London papers and then by the New York Times, which ran it with the lurid headline “Nazi ‘Heavy Water’ Looms as Weapon.” This was the last thing the security-conscious Manhattan Project leaders needed.

  Worried that the Norsk plant would soon resume production, Conant and Groves kept up constant pressure, which led the American Eighth Air Force to conduct a major bombing raid on Rjukan in November 1943. Even though it managed only two direct hits on the electrolysis plant, the Germans believed more attacks would follow, and dismantled the setup and moved it within the safety of their own borders. A few months later, a ferry carrying the remaining forty drums of Rjukan heavy water—roughly 3,600 gallons—destined for German research laboratories was sunk by commandoes, sending the precious cargo to the bottom of a mountain lake in Norway.

  Eager to strike another blow against the Nazi bomb program, Groves asked Conant and Bush to investigate all the power plants in Germany that might be involved in heavy water production. When this task proved unwieldy—there were too many facilities that could easily be diverted to weapons work—Conant compiled a new list of important “S-1 targets” in Germany for army air forces bombers. Alarmed by new intelligence reports warning of a “German process” that sounded very much like atomic fission, he switched his attention from factories and power plants to research centers. Drawing on his intimate knowledge of the country, Conant identified the names of leading German scientists and the locations of chemistry laboratories where they were thought to be working on nuclear physics. At the top of his list were the Berlin laboratories of Otto Hahn and Werner Heisenberg, which he knew would be the beating heart of any German bomb effort.

  On June 24, 1943, he wrote Bush that “the chances of seriously interfering with the German war effort by the demolition of targets 1 and 2 are very considerable.” He also singled out the other branches of the Kaiser Wilhelm Institute spread throughout Germany as key sites, and, by extension, the scientists who ran them, but they were not as critical and could be attacked when convenient. Later the same day, Bush met with Roosevelt and told him the German targets had been pinpointed and “arrangements are now under way.”

  The focus on Heisenberg intensified with Bohr’s arrival in the United States on December 6. He made it his personal mission to spread the word that the Germans were on a path to a bomb, and using Heisenberg’s approach might be within reach of success. He had in his possession a drawing, given to him by his former friend and colleague in the fall of 1941, that he believed was evidence the Germans had figured out how to produce a chain reaction. During the two weeks he spent in Washington, Bohr confided his fears to British diplomats as well as to Supreme Court Justice Felix Frankfurter, who quietly conveyed them to the president. On December 27 Bohr and his son took the train to Chicago, where they were met by Groves. During the two-day trip to New Mexico, Bohr talked incessantly about German developments to Groves, who was seriously alarmed by the drawing he showed him.

  On December 31 Oppenheimer convened an emergency meeting of the project’s top scientists to consider whether Heisenberg’s primitive sketch could be interpreted as a design for a German atomic bomb. The crude picture showed a box with horizontal lines or sticks coming out of the top that suggested control rods. “It was clearly a drawing of a reactor,” recalled Bethe. “When we saw it, our conclusion was that these Germans were totally crazy—did they want to throw a reactor down on London?”I While no complete assurance could be given, Oppenheimer informed Groves that their considered opinion was that the arrangement of the materials suggested by the drawing would be “a quite useless military weapon.” But the physicist Jeremy Bernstein, who has made a careful study of the Heisenberg sketch, maintains that the Germans were far from crazy. “If the people at Los Alamos had realized—which they didn’t—that the Germans knew about plutonium, their concern about the German program, which was always considerable, might well have approached the panic level.”

  At a time of war, fear is contagious. Bohr’s apprehensions, expressed repeatedly, accrued credibility and added to the project leaders’ sense of urgency and concern that the Germans might be winning the race to the bomb. In late 1943 Groves summoned his security chief, Colonel John Lansdale, to his office and told him he had received a proposal that an attempt should be made to kidnap or assassinate Heisenberg. He said he had been advised that the removal of the brilliant German physicist would hurt or even cripple the Nazi bomb program and asked bluntly, “What do you think?”

  Although Lansdale told him he thought any attack along those lines would almost certainly fail, Groves could not let go of the idea of disrupting Germany’s atomic program by going after the nuclear scientist, according to Thomas Powers, author of a fascinating account of Heisenberg’s wartime role. Groves had seen Conant’s target list, and it coincided with similar ideas suggested by refugee scientists determined to prevent Hitler from getting his hands on a bomb. By late 1943, Groves and Bush were ready to make the case to Major General George Strong, the army’s assistant chief of staff for intelligence, that an important goal of bombing the Berlin laboratories would be “the killing of scientific personnel employed therein”—meaning Hahn and Heisenberg.

  Conant, according to Powers, “very probably knew” of the plot to elimin
ate Heisenberg, which over a period of months escalated from kidnapping to assassination, received high-level approval, and was assigned to the OSS. There is no record of whether he condoned the scheme that a year later led to an agent being sent to Zurich with instructions to shoot Heisenberg while he was delivering a physics lecture “if so much as a word suggested that the Wunderwaffe [“wonder weapon”] up Hitler’s sleeve was an atomic bomb.” Heisenberg never mentioned anything related to the bomb in his talk on December 18, 1944, so no action was taken, although the original proposal led to the German physicist being arrested on May 2, 1945.II

  As Powers points out, it seems extraordinary that Conant and Bush, as civilian scientists, should have been asked by the military to name their coequals in Germany with the express purpose of having them killed. Yet if there was a chance that eliminating one or two individuals could slow or halt the enemy’s progress to a weapon, how could they do otherwise? Neither man ever wanted their involvement in the cold-blooded campaign to disrupt the German atomic program known, and both omitted it from their memoirs. It was not their proudest hour. But in the heat of war, with all the uncertainty about the imminence of a German bomb, “almost any effort to stop Heisenberg and Hitler would have been fully justifiable,” writes Powers. “All we can say with fairness at this remove is that strange things may seem reasonable to men who know only enough to fear the worst.”