THE TUBE ALLOYS COMMITTEE met on April 23, 1942, at Old Queen Street in London, gathering in a seventeenth-century townhouse with tall windows and a fine view of the early spring in St. James’s Park below. As usual, the scientists, led by Wallace Akers, former research director at Norsk Hydro’s rival Imperial Chemical Industries (ICI), had a lot to talk about: experimental work on fusing a bomb, cooperation with the Americans, the expansion of a model isotope-separation plant, and further orders of uranium oxide. As at every meeting, they discussed the Germans, but this time with heightened urgency.
Since 1939 the British scientific establishment had feared the Nazis would obtain an atomic bomb. Hitler’s invasion of Poland, then his boast that he would soon “employ a weapon” for which there was no answer, made the danger that much more imminent, prompting Sir Henry Tizard, head of the Air Ministry’s research department, to investigate the production of a British bomb. As the government’s chief scientific adviser, charged with developing new technologies like radar, Tizard’s word carried a lot of weight. And so the inquiry began.
Two young physicists, Otto Frisch and Rudolf Peierls, both Jewish refugees from Germany, put the British firmly on their path. On March 19, 1940, their report, “On the Construction of a Super Bomb,” landed on Tizard’s desk like a thunderclap. Frisch and Peierls detailed how little more than one pound of pure U-235 — divided into two (or more) parts that were then smashed together at a high velocity — would initiate an explosion that would “destroy life in a wide area... probably the center of a big city... at a temperature comparable to the interior of the sun.” Then they raised the specter that German scientists might soon “be in possession of this weapon.” The only way to counter this threat, they concluded, was for Britain to have the technology as well.
The following month, the British government launched the MAUD Committee. Exploratory research began with some of its preeminent scientists, as well as Peierls and Frisch. Foremost, they proposed building a plant to separate rare U-235 from its cousin U-238. This plant would cost as much as a battleship. In July 1941 the group delivered a road map for an atomic bomb program. Tizard remained skeptical, particularly as to its cost. He thought it best the Americans handle everything. But the project now had a champion in Lord Cherwell, the Oxford physicist who Churchill said could “decipher the signals from the experts on the far horizons and explain to me in lucid homely terms what the issues were.” On August 27, 1941, Cherwell recommended moving forward with producing the first bomb within two years. The experts gave the project 10–1 odds of success, but Cherwell told the prime minister that he would bet little more than “even money.” He continued, “It would be unforgivable if we let the Germans develop a process ahead of us by means of which they could defeat us in war or reverse the verdict after they had been defeated.”
Churchill wrote to his War Cabinet, asserting, “Although personally I am quite content with the existing explosives, I feel we must not stand in the path of improvement.” The cabinet agreed, promising “no time, lab-our, material or money should be spared in pushing forward the development of this weapon.” Thus the Directorate of Tube Alloys was formed.
Throughout this period, fears over the German bomb persisted. From far and wide came whispers, rumors, threats, and fact — which, mixed together, made for the typically confusing brew that governments called “intelligence.” Two German pilots were overheard on a tram speaking about “new bombs” that were “very dangerous” and had the power of an earthquake. One German émigré physicist warned that there was pressure from high within the Nazi government to build a bomb and that the Allies “must hurry.” Another warned that the Wehrmacht had taken over the Kaiser Wilhelm Institute of Physics. A military attaché in Stockholm reported, “A tale has again reached me that the Germans are well under way with the manufacture of an uranium bomb of enormous power, which will blast everything, and through the power of one bomb a whole town can be leveled.” Other reports chronicled a mysterious September 1941 meeting where Werner Heisenberg admitted to Niels Bohr, who was living in Nazi-occupied Denmark, that a bomb could be made, “and we’re working on it.”
The effort to obtain further intelligence was largely the territory of Eric Welsh. From the Griffin the British had some insight into machinations in Berlin. Peierls and Frisch also provided hints of German interest in a bomb by culling lists of German physicists and dissecting any papers they published on atomic research. Again, these added ingredients to the brew, but nothing definitive.
The best intelligence the British received came through German activity at Vemork. As early as April 1940 Jacques Allier had alerted his British allies to Nazi efforts in uranium research using heavy water from the plant. After the occupation of Paris two months later, the Norwegian supply of 185 kilograms under Joliot-Curie’s care was secreted out of the country aboard a British ship before the Germans could seize it. The twenty-six flasks were hidden in Windsor Castle until the Tube Alloys scientists began their own experiments with the material.
The continued German focus on heavy water into 1942 was of even greater importance because of a newly discovered element called plutonium. The British were centering their efforts on isotope separation to produce enough pure U-235 for their bomb. But British and American scientists knew this was not the only path toward an explosive. In mid-1940, before the curtain of censorship fell completely, a widely published paper in the Physical Review revealed that when uranium (atomic number 92) is bombarded by neutrons, some split the rare isotope U-235 nuclei but others are absorbed by the much more prevalent U-238 nuclei, transmuting it into the isotope U-239. This unstable isotope decayed by what was called beta emission, which had the effect of increasing the number of protons in the nucleus by one while reducing the number of neutrons by the same amount. This new element, neptunium (atomic number 93), readily decayed once again, creating yet another element, but a stable one: plutonium (atomic number 94).
As further Allied experiments showed, but now in classified reports, plutonium was fissile, similar to U-235, and could be used as explosive material. However, unlike U-235, plutonium was chemically different from uranium, and thus the two were more easily — and much more cost-effectively — separated. If one managed to engineer a self-sustaining reactor with uranium and a moderator, it would breed enough plutonium that could then be extracted to help build a bomb. This kind of reactor, Allied physicists theorized, required between three and six tons of heavy water. Through Leif Tronstad, the British knew the Germans were attempting to produce similarly large quantities of heavy water at Vemork.
At the April 23 Tube Alloys meeting, Akers and his group of scientists discussed the findings of a new SOE source in Norway (a quick-working Skinnarland). According to his coded messages, heavy water production was up to 120 kilograms a month — and increasing. Something, the men at Old Queen Street decided, must be done, and soon. In the minutes of their meeting sent to Churchill’s War Cabinet, they stated, “Since recent experiments have confirmed that element 94 would be as good as U-235 for military purposes, and since this element is best prepared in systems involving the use of heavy water, the Committee recommends that an attempt should, if possible, be made to stop the Norsk Hydro production.” If Vemork had not been a significant target before, it was definitely one now.
*
In the weeks that followed, Tronstad suddenly found himself preoccupied with heavy water. On May 1 Wilson sent him a note, asking him to determine where and to whom in Germany Norsk Hydro delivered its supply from Vemork. The same day, he consulted with Akers on the construction of a British heavy water plant. Soon after, he sat down again with Eric Welsh, who wanted him to set up a spy network, both inside and outside Vemork.
Skinnarland was already providing good intelligence, but it simply wasn’t enough. The Tube Alloys Committee speculated that the Nazis were pursuing a reactor to produce plutonium, a sure road to a weapon, and everything must be known about their activities. Germany was largely closed to intelligence work, but Nazi scientists traveled to Vemork, Oslo, and Stockholm — places where Tronstad had close contacts.
On May 11 Tronstad wrote two letters, the urgency in his tone clear. The first was to “the Master”: Jomar Brun. Tronstad requested detailed sketches, diagrams, and photographs of the Vemork plant, as well as production figures — anything Brun could discover about the German use of “our juice,” and the specific address where it was sent “so we can give our regards to the people there.” Tronstad wrote: “You can take this as your war effort! It must be pursued with all means.” He signed the letter Mikkel, “the Fox,” his new alias on coming to Britain.
Tronstad addressed his second to Harald Wergeland, his former student and now a University of Oslo professor. Wergeland had studied under Heisenberg and was close to several other German scientists. Addressing him as “My Dear Young Friend,” Tronstad wrote, in thinly veiled code, “We must know if the Germans have managed to tame the very smallest creatures.” He wanted to know everything Wergeland had learned from his recently reported trip to meet with Niels Bohr. Tronstad instructed him to insinuate himself into the Nasjonal Samling Party, then to attempt a research trip to Germany to “soak up everything possible as quickly as possible.”
When these letters were brought to Welsh, Tronstad demanded that SIS and the SOE be sure to keep strictly separate communication lines with Skinnarland and with Brun at Vemork. No connection between the two men must be suspected. They did not want another atrocity like the one that had recently happened at Telavåg.
Almost a month before, the two British services had both used the coastal island village southwest of Bergen as an entry point for their operations. On April 17, two Kompani Linge men arrived by boat into Telavåg to organize resistance groups and conduct sabotage operations. The Gestapo was already on alert after some SIS agents had been seen in the area days before. Some loose talk and gifts of British flour gave away the presence of the Linge men. They were cornered in a house, and a shootout followed. One of them died, the other was captured, and a Nazi SS officer was killed. Reichskommissar Terboven was incensed at the brazen action and by the discovery of arms depots in the village. Norway was under his control, and he would see that this much was clear to all its people by making an example of Telavåg.
He ordered the village razed and personally watched it happen: every house and building burned down, every boat in the harbor sunk, every animal killed, and the entire community — men, women, and children alike — sent to various concentration camps. Terboven also had eighteen citizens who were caught trying to escape executed by firing squad. He was dutifully following Goebbels’s recommendation: “If they can not learn to love us, they should at least fear us.”
Tronstad feared the same would happen to those he had tasked with spying for him. Such thoughts weighed heavily on him, especially since he slept safely at night in a house beside the expansive Hampstead Heath while some of his countrymen were in constant jeopardy.
*
If Lillian Syverstad was stopped by a German soldier, and there were always German soldiers patrolling Rjukan, she would simply say that she was on her way to visit her sister, Maggen, who was married to the assistant dam-keeper Torstein Skinnarland up on Lake Møs. Lillian, a pretty eighteen-year-old, worked in the town’s bookshop, and she could smile and charm her way out of most situations. That particular June day, she carried a folded note, which had been passed to her by a friend in town. It was likely from her brother Gunnar, a laboratory assistant at Vemork, but Lillian never knew — and never looked to see — what the messages were. It was for the best. She could not confess what she did not know. Once she reached the dam, she made sure nobody was watching, then left the note behind a simple round stone. Soon afterward, Lillian’s childhood friend, Einar Skinnarland, retrieved the note, and yet another scrap of intelligence on Vemork was collected.
On the night of his parachute drop into Norway, a strong northwest wind had blown Skinnarland into a rocky hillside. He hit the ground hard, his spine compressing like an accordion. When he stood and gathered his parachute, he felt something pop in his lower back, but there was nothing to be done about it. He quickly found the small package that had been sent out after him, but the tube container with the weapons was nowhere in sight. Finding it in the dark was hopeless.
From the silhouette of Mount Gausta, Skinnarland reckoned he was at least ten miles northwest of Lake Møs. His back shooting with pain, his knee still tender, he made his way through the craggy mountains toward home. He arrived just before dawn. Only his brother Torstein knew where he had been. The rest of his family greeted him warmly and asked how his long hunting trip had gone. He begged off any questions about his stiff back, and there was little time for a reunion.
Skinnarland set off on skis to meet his friend and confidant Olav Sko-gen, operating out of a mountain lodge halfway to Rjukan. The local Milorg leader, with a shock of dark, curly hair swept high over his broad forehead, guessed from the outset where Skinnarland had been. Hearing about the drop, Skogen stressed the need to find the container of weapons he’d been supplied as quickly as possible. The two set off for the drop site but found nothing. The container was likely hidden in a drift of snow and would never be recovered.
Skinnarland returned to his job building a dam at Kalhovd, eighteen miles north of Lake Møs. There was little time to see Gudveig, who lived in Bergen, but now and again he sent her letters, saying nothing of his undercover work. He began gathering intelligence on Vemork, partly through his own reconnaissance but mostly through his contacts inside the plant.
*
Skinnarland did not know it, but Jomar Brun was also providing a wealth of information about Vemork to London. On October 3, 1941, Paul Harteck and another German scientist had traveled to Rjukan with Consul Erhard Schöpke. A Nazi zealot with the medal-bedecked uniform to match, Schöpke was responsible for exploiting the country’s industry for the Third Reich as a member of the Wehrwirtschaftsstab Norwegen (War Economy Staff for Norway). Accompanying them was Bjarne Eriksen; Norsk Hydro’s former lawyer had replaced Axel Aubert as director general on his retirement. Despite the company’s earlier support of the Allies, Eriksen had essentially taken the position since the occupation that the firm’s survival was more important than patriotism — or, as some of its workers said more bluntly, “Long live Hydro... To hell with Norway.”
After Brun gave a tour of the heavy water plant, the men gathered in the stately administration headquarters in Rjukan. They enjoyed a nice dinner and then, around a warm fire, smoking cigars and sipping whiskey, Schöpke got to the business at hand. Production numbers were off and something needed to be done. In the twenty months since the Germans invaded, Vemork had delivered 390 kilograms of heavy water, despite German orders of 1,500 kilograms a year. Not only was Norsk Hydro falling far short of the first target, but the company needed to more than triple production, to 5,000 kilograms a year.
Then Harteck spoke. There were two ways to increase production to such a level. First, they could expand the electrolysis plant as it now operated, adding more electrolyzers to the initial cascade and doubling the size of the high-concentration plant. Second, they could test and institute a new technology (catalytic exchange) that held out the promise of not wasting the deuterium burned off as gas during electrolysis. In the end, they decided to do both.
Brun was instructed to develop a plan to institute these ideas. Unwilling to help, and still unsure of why the heavy water was needed, Brun dragged his feet. In the months before, he had actively slowed production by contaminating the high-concentration cells with cod-liver oil, making the heavy water foam. He could not continue interrupting production this way without exposure, however. In January 1942 he was ordered to Berlin. At the Army Ordnance Department in Hardenbergstraße 10, he endured more meetings and more demands for increased production, chiefly from one Dr. Kurt Diebner. When Brun asked Diebner what was the purpose of such quantities of heavy water, Diebner answered they would be sent to the “quinine factory” to make a refreshing tonic. Brun was not amused.
Over the next several days, Brun worked with Harteck to formulate the way forward at Vemork. The plant revisions needed to be implemented immediately, no matter the cost. With the improvements, Harteck figured they could produce at least eight kilograms a day. Further, Brun was told, Norsk Hydro needed to consider constructing heavy water plants at two other hydroelectric power stations: Såheim (in Rjukan proper) and in Notodden. They were smaller power plants, with more limited electrolysis facilities, but together they could add another six kilograms a day, bringing total production to five thousand kilograms a year, possibly more.
Some of the scientists Brun met in Berlin sympathized with Norway’s plight and spoke quietly of their disgust with Hitler. They warned Brun to be careful of what he said to whom, particularly to the more ardent Nazis such as Diebner. Even so, none of them would reveal what they needed the heavy water for, although they assured him it was not for the war. It was a disturbing trip. Too often Brun heard the phrase “Heil Hitler.” Signs on the trams warned of enemy ears. There were only spare amounts of food at the Kaiser Wilhelm Institute’s canteen, and the offices were barely heated. One day, Brun passed several young Jewish girls on a corner who had yellow stars sewn onto their shirts.
On returning home, Brun had no choice but to begin instituting the expansion. Workers doubled the number of high-concentration cells to eighteen. The nine-stage cascade, already huge, grew to include over forty-three thousand cells. In addition, Brun started a pilot test of the catalytic exchange process, and plans were developed for Såheim and Notodden.
In May, Terboven visited Vemork, then Harteck returned to refine his new exchange method before it was finally implemented. Production was up — from an average of 80 kilograms a month in December 1941 to 130 kilograms in June 1942 — and still rising. Såheim and Notodden were soon to be operational as well.
All this information and more Skinnarland and Brun, operating independently, sent in coded messages through a system of couriers to Oslo, then on to Sweden. Some were secreted inside toothpaste tubes. Others were taped to the backs of the messengers bringing them across the border. Then they were sent by plane to London, where they made their way to Chiltern Court.
One report from Skinnarland detailed the meager security at the plant, stating that the Germans “depend too much on the surrounding natural defenses. The night guard is usually Georg Nyhus, a middle-aged, decent fellow. A neighbor. He should not be hurt. His only job is to check the permits of workers through his window, after they have been cleared by the two sentries on the bridge.”
Another from Brun, labeled “High Concentration Plant for Enrichment of Glucose,” included an inventory of the plant down to the lead pipes, sand seals, rubber connections, and flanges of the high-concentration cells. Microphotographs of building blueprints, detailed drawings of equipment, and production figures followed. It was everything one might need to build a heavy water plant, or indeed to destroy the only one in existence.
*
On June 4, 1942, Kurt Diebner watched a line of guests — some in fine suits, others in uniform — file into the lecture room at Harnack House, headquarters of the Kaiser Wilhelm Institute. In addition to scientists involved in atomic research, the attendees included General Emil Leeb, Admiral Karl Witzell, and Field Marshal Erhard Milch, respectively the armaments chiefs of the German army, navy, and air force. The hawk-eyed Albert Speer, the newly appointed minister for armaments and war production, had called them together to decide the future of the atomic program. Even though this had been launched on Diebner’s initiative, it was Heisenberg who took to the stage to present their findings, sidelining Diebner.
In the first two years of the Uranium Club’s existence, they had made steady advances in atomic science. Thanks to the Nazis’ military successes, they had an easy channel to Vemork’s heavy water, a substance made all the more important by the final determination that it was both superior to graphite as a moderator (based on a mistaken calculation by one of its chief scientists, Walther Bothe) and easier to obtain in a highly purified form than the carbon product. They also had access to tons of Belgian uranium ore and a cyclotron in Paris commandeered from Frédéric Joliot-Curie to experiment with subatomic-particle collision.
Over seventy scientists, distributed over a number of institutes, were pursuing basic but necessary research on everything from the energies of fission products, to several methods of U-235 isotope separation, to the construction of a uranium machine, to, finally, the likelihood of a new fissile material created from such a machine: element 94 (what the Americans were calling plutonium). They had broken ground on a new laboratory next to the Kaiser Wilhelm Institute of Physics (dubbed the Virus House to discourage unwelcome visitors). All looked bright for the future.
Of all the developments, the most exciting related to the construction of a uranium machine. In Leipzig in September 1941, with assistance from Heisenberg, Professor Robert Döpel built a small spherical machine with two concentric layers of uranium oxide and heavy water, a beryllium neutron source at its core. They submerged the sphere in a vat of water and awaited the test results. The increase in neutrons was small, but it was there, evidence that the machine was successfully splitting U-235 atoms. With more layers of heavy water and higher-grade uranium, Heisenberg knew “in his bones” that they would have a self-sustaining pile. From that point forward, he said, there was “an open road ahead of us, leading to the atomic bomb.” Diebner agreed. In his mind, success was now a matter of shifting all their basic research into an industrial program.
But two months later, with the Russians counterattacking on the Eastern Front and Hitler calling on Germany to focus on meeting the short-term demands of the war, Erich Schumann, Diebner’s supervisor and no fan of “atomic malarkey” from the start, called for another review of the research. On December 16, Schumann recommended to his generals that responsibility for the program be handed over to the Reich Research Council, the civilian-run, industry-centered body for basic and applied scientific research. A weapon, even if achievable, was still too far off, Schumann determined. The generals punted a decision to a second conference in February 1942. By then, one of the council’s lead scientists, Abraham Esau, was already being put forward as a potential new head of any overall group. A pioneer in wireless telegraphy, professor of physics, and a man of considerable influence in the Reich, Esau had been stripped of fission research by the army when Diebner was made head of the Uranium Club in 1939. Now he looked poised to have his revenge.
For that second Army Ordnance conference, held on February 26, Diebner made his case in an exhaustive 131-page report. “In the present situation, preparations should be made for [harnessing] atomic energy... all the more in that this problem is also being worked on intensively in the enemy nations, especially in America.” With five tons of uranium metal and heavy water, and a self-sustaining machine, “a bomb of the greatest effectiveness” using between ten and one hundred kilograms of plutonium was in sight. Diebner offered a step-by-step plan to reach this goal. He simply needed the manpower, supplies, and capital to achieve it.
The very same day, the Reich Research Council held its own meeting on atomic physics with Hahn, Heisenberg, and Esau as lead speakers. Attendees at the conference came away impressed at the technology’s future potential. Goebbels wrote in his diary, “Research in the field of demolishing atoms is so advanced that its results can perhaps be used for waging this war. Here tiny efforts result in such immense destructive effects that one looks forward with horror at the future course of this war.”
But the army generals remained unconvinced. Diebner could not promise success with certainty. Unable to justify such expense and effort without the guarantee of a weapon within a year, the army forfeited control of the Uranium Club to the Reich Research Council. A further blow for Diebner came when Heisenberg was chosen to be the new director of the Kaiser Wilhelm Institute of Physics, and Diebner was forced to vacate his offices there.
Four months after the shakeup, Diebner still believed there was a chance for an industrial-scale program. Speer, who had maneuvered the project within his sphere of influence, had called the June 1942 meeting at Harnack House to decide how much backing he should give it.
Heisenberg took the stage to present the scientists’ findings. Tall, blue-eyed, with a sweep of straw-colored hair, he commanded the room in a way Diebner never could. He began by giving a theoretical overview of atomic science, then dove down into the specifics of isotope separation, uranium machines, and the production of plutonium. Then he hit his audience with the potential of the technical application of this science. With a uranium machine, they could “power ships, possibly even aircraft, with the greatest imaginable range.” With plutonium, they could produce explosives that “will be a million times more effective than all previous explosives.” One general, who had visions of dropping bombs on New York, wanted to know how big such bombs would be. Heisenberg cupped his hands and said, “About the size of a pineapple.”
Heisenberg then shifted to downplaying expectations. They were still at the basic research phase, he said. More theory needed to be developed, more experiments performed. There were many obstacles standing in their way as well, including supplies of heavy water. One day, far in the future, a bomb might “turn the tide of war,” he concluded; but first they needed a working reactor, and that was a long way off.
Speer then asked how much money their project needed. Heisenberg proposed a sum of 350,000 marks — in effect, nothing at all. There were other programs, namely V-1/V-2 flying bombs, whose scientists had demanded billions of marks and tens of thousands of workers in order to complete their projects and see them put to use in the war. Speer was flabbergasted, Diebner furious that Heisenberg would ask for such a trifling sum. If one was certain of a pineapple-sized bomb deciding the war, and if one was bent on producing it, much more would be needed to bring it to fruition.
After the meeting, Speer steered his backing toward programs like flying bombs that he believed would most benefit Germany’s immediate war strategy. Basic research on harnessing atomic power would continue. The Reich Research Council would lead the project, and Army Ordnance would help fund it. Scientists would have ready access to supplies, and they would remain exempt from military service to do their work. But unless there was reason to reconsider, all this research was focused on future potential. There would be no massive project to see it made of any use in this war.
Diebner was undeterred. He returned to his research at Army Ordnance’s Kummersdorf Testing Facility in Gottow, fifteen miles southwest of Berlin. With a host of young physicists he had recruited in the first days of the program, he quietly continued building his own uranium machine with a very different design from the ones that others had engineered. Hard and fast, he pressed on toward a bomb.
*
Prime Minister Winston Churchill chewed on a cigar as he stared out at the Atlantic’s moonlit waters on June 17, 1942. Seated in the cockpit of a Boeing Clipper flying boat, he had many matters weighing on his thoughts as he flew toward the United States. The whole of continental Europe remained under Hitler’s heel, and though British and American bombers pummeled Germany night after night, only a cross-Channel invasion could liberate the Continent. But Churchill knew that Allied forces were far from ready for such an attack. He must convince the U.S. president, Franklin D. Roosevelt, to delay an invasion — one of the two key purposes for his twenty-eight-hour journey across the Atlantic. The other was to discuss atomic bombs.
After a glass of champagne and a restless nap, Churchill fastened his seat belt for landing beside his trusted chief pilot, Rogers. The Clipper glided past the Washington Monument and landed on the Potomac. In the capital he met with General Marshall, and the next morning Churchill flew up to Hyde Park, New York, the site of Roosevelt’s family estate. The American president greeted him on the tarmac. Physically, the two men were a study in contrasts: the short, feisty British bulldog beside the tall, smooth American lion. But Churchill and Roosevelt were both intellectuals as well as cunning politicians, and they shared the terrible weight of leading their people through a great war. They were also good friends.
Driving his blue Ford Phaeton, which featured special hand-controlled levers to accommodate his physical disability, Roosevelt whisked his guest off on a hair-raising tour along the Hudson River bluffs. For two hours they spoke of the war, and Churchill was encouraged by how much more they settled zipping across the estate than they would have done on opposite sides of a crowded conference table.
Earlier that week, Roosevelt had read through a report that set out a plan for a massive U.S. Army program to build atomic bombs. His chief scientific adviser, Vannevar Bush, who’d founded Raytheon, was spearheading the effort, with an estimated cost of $500 million.
The program’s genesis mirrored in many ways the British Tube Alloys program. In August 1939 Albert Einstein, in contact with a group of scientists who had recently emigrated from Europe, sent a letter to Roosevelt warning of the need to exploit the explosive potential of fission before the Germans did. A “Uranium Committee” of leading physicists was formed, and over the next two years, with limited funds but a lot of ambition, they conducted research, welcomed insight from the British, and concluded that a devastating new weapon was indeed possible — and that there were several potential routes to success. By summer 1942, word had come from Europe that the Germans might have already realized a working nuclear reactor — something the United States had yet to achieve. As one scientist wrote Bush, urging a decisive American effort, “Nobody can tell now whether we shall be ready before German bombs wipe out American cities.”
With a handwritten note that simply read “Ok. V.B.,” Roosevelt approved the development of the program, which was codenamed the Manhattan Project. In typical American bigger-is-better fashion, its leaders decided that every route to a bomb should be pursued, including using heavy water reactors, plutonium, and U-235 isotope separation.
On June 20, Roosevelt and Churchill held a meeting in a small, dark study that faced the front porch of the Hyde Park mansion. Once Roo-sevelt’s children had used the space as a classroom, but now it was his quiet hideaway, with bookshelves and nautical prints on the walls and a huge oak desk that took up most of the space.
Churchill sat, a globe beside his feet, and got straight to the point. “What if the enemy should get an atomic bomb before we did!” he later wrote, recounting the meeting. “However skeptical one might feel about the assertions of scientists, much disputed among themselves and expressed in jargon incomprehensible to laymen, we could not run the mortal risk of being outstripped in this awful sphere.” Their two countries needed to “pool our information, work together on equal terms, and share the results, if any, equally between us.” If Churchill expected a debate, he didn’t get one. Roosevelt agreed wholeheartedly with the proposal, and given the ongoing Nazi bombing raids on Britain, they decided that the United States should be the center of activity.
They also discussed the German focus on producing heavy water — “a sinister term, eerie, unnatural,” Churchill later said. A few days after the prime minister flew back to London, the War Cabinet put forward plans, of the highest priority, for a raid on Vemork.