Truman and Byrnes were living in a fool’s paradise. Their atomic diplomacy would only accelerate the postwar arms race Stalin had already initiated to catch up with the United States. On August 20, 1945, just five days after the surrender of Japan, Stalin had secretly ordered an all-out, no-expense-barred program to build a Soviet bomb. That July 24, at the last Big Three conference in the Berlin suburb of Potsdam, Truman, exultant at Groves’s awesome description of the Trinity test, had approached Stalin with contrived casualness as the Soviet dictator was leaving the conference room. Truman had said that the United States “had a new weapon of unusual destructive force.” Stalin had simply nodded his thanks and left the room. Truman and Churchill decided that Stalin had not understood. They were wrong. Stalin was well briefed on the Manhattan Project. The latest yield of Soviet espionage, a memorandum he had apparently received a couple of weeks before, had informed him, among other things, that the Trinity test was imminent.

Soviet intelligence had thoroughly penetrated the Manhattan Project. The gumshoes in the U.S. Army Counter Intelligence Corps, fixated on the left-wing connections of J. Robert Oppenheimer, who was in charge of the Los Alamos Laboratory, where the bomb was built, and those of several other scientists, never suspected the real spies. At Los Alamos itself the Soviets had the ideal intelligence setup—two physicists in critical positions reporting independently, neither aware that the other was a spy. Stalin’s spymasters at Moscow Center in NKVD headquarters (the initials stand for the Russian words for People’s Commissariat for Internal Affairs) at the Lubyanka Prison could thus confirm what they received and pass it on to their own superiors, who in turn passed it to Soviet physicists, confident that the information was accurate. Both spies were “walk-ins,” volunteers who approached the Soviets on their own, and both spied out of idealism, not for pay.

A third spy, George Koval, gained wide access to the industrial processes involved in nuclear armament by penetrating plants at Oak Ridge, Tennessee, and Dayton, Ohio, where bomb components were manufactured for shipment to Los Alamos. Born in Sioux City, Iowa, to a family that immigrated in 1932 at the height of the Depression to a secular Jewish colony established in the Soviet Union, Koval was recruited by the GRU, the Soviet military intelligence service, and slipped back into the United States as a mole in 1940. His story did not emerge until 2007, after he died in retirement in Moscow in his nineties and President Vladimir Putin posthumously awarded him the highest post-Soviet decoration, Hero of the Russian Federation.

One of the two spies at Los Alamos, Klaus Fuchs, who had fled to England from Hitler’s Germany in the 1930s, is well known, because he confessed in 1950 after U.S. military code breakers had cracked enough of the Soviet wartime espionage cable traffic to lay suspicion on him. By then he was chief scientist at Britain’s top secret Harwell nuclear center. He was tried and sentenced to fourteen years in prison, the maximum allowable under British law because the Soviet Union was an ally at the time of his spying. He was released after nine to spend the rest of his years, until his death in 1988, doing research unrelated to weaponry at a nuclear institute in East Germany. (Another well-known Soviet spy at Los Alamos was David Greenglass, the brother-in-law of Julius Rosenberg, who recruited him. Rosenberg was himself engaged in industrial spying for the Soviets at war plants on the East Coast, stealing the secrets of such new weapons as the proximity fuse. Greenglass was an Army enlisted man, a machinist by trade, who worked in the conventional explosives division of the Los Alamos complex. He was a man of limited education and none in physics and his often garbled reports, while sufficient to put Julius and his sister, Ethel, in the electric chair, provided Moscow with as much confusion as they did information.)

The second physicist spy for the Soviets at Los Alamos, Theodore Hall, has been little noted because he escaped prosecution and even the embarrassment of disclosure until 1995, when the first fruits of the code breaking, the so-called Venona documents (Venona was the code name of the code-cracking project), were made public. The rest followed in 1996. Hall was a mathematics and physics prodigy from New York who transferred to Harvard as a junior from Queens College at the age of sixteen, stood out among his peers, and became one of the youngest physicists to work at Los Alamos after he was recruited close to his eighteenth birthday. Hall’s case was particularly ironic because, while he aided and protected the Soviet Union by committing treason, his equally brilliant brother, Lieutenant Colonel Edward Hall, devoted himself to threatening its existence as the U.S. Air Force’s leading engineer in the post-Second World War development of rocket engines. Edward Hall played a vital role in the creation of the first American intercontinental ballistic missile force after Schriever enlisted him as a member of his original ICBM team in 1954. He never knew of the treason of his brother, Theodore, until it was revealed forty-one years later when both men were in the evening of their lives.

Fuchs was the more informative of the two spies because he was a senior physicist, in knowledge if not in years, when he arrived at Los Alamos in August 1944 at the age of thirty-three. He was therefore able to furnish Stalin’s intelligence officers with a fully detailed description, including drawings with exact dimensions, of the plutonium bomb dropped on Nagasaki. Indeed, Fuchs had been brought to Los Alamos at the initiative of Hans Bethe, another German émigré physicist and subsequent Nobel Laureate, who was in charge of the Theoretical Division, precisely to help solve the most sensitive and secret problem on the laboratory’s agenda in 1944—the implosion method required to detonate that same plutonium bomb. And Fuchs had done his work well. “One of the most valuable men in my division,” Bethe was later to remark of him with chagrin.

Little Boy, the code name of the atomic bomb dropped on Hiroshima, was a so-called gun type. (The code name was drawn from the relative slimness of the bomb’s casing at twenty-nine inches, even though it weighed 9,700 pounds and was ten feet long. The Nagasaki bomb was, in contrast, code-named Fat Man because of the wide girth of its casing. It was not, however, much heavier than Little Boy, weighing 10,000 pounds.) Little Boy had an internal cannon that used a conventional explosive, cordite, to fire a bullet of enriched uranium, an isotope called U-235, into three larger rings of the same isotope stacked one atop another at the muzzle of the cannon. U-235 is so fissionable that when the bullet hit the rings, it set off a nuclear explosion of immense force. The design was simple and Robert Oppenheimer and the other scientists at Los Alamos were so certain it would work that they didn’t feel it was necessary to test it.

The rub was that there was a shortage of uranium. Although there were plentiful underground deposits of the naturally occurring substance in the American West and in Canada, exploration for uranium deposits and mining them had hardly begun. The manufacturing process to turn natural uranium into the highly enriched isotope was also so slow that if the scientists relied on U-235 and the gun-type design, the United States would be able to produce only one atomic bomb by 1945. To create more atomic bombs, Los Alamos had to use plutonium as the nuclear core. Plutonium, however, was much more difficult to bring to supercriticality than U-235 because of a phenomenon called spontaneous fission, which resulted from an impurity inherent in the manufacturing process. If it was used in a gun-type weapon, the bomb would fizzle. The method finally decided on was implosion—surrounding the plutonium core with conventional explosives and compressing it with such speed and simultaneousness that the plutonium became supercritical and a nuclear explosion occurred. The concept was simple; designing and executing it was extremely complicated.

The Soviets were to face the same shortage of uranium for the same reason—they had also not yet located and developed mining of natural uranium deposits in Siberia. To create an arsenal instead of just one bomb, they would have to employ plutonium for the cores. And later, after the Trinity test and the dropping of the bombs on Hiroshima and Nagasaki, it was determined there was a second reason to use plutonium. Once the implosion method was mastered, the plutonium weapon yielded considerably greater nuclear force and devastation than the gun type with U-235. The Little Boy bomb that destroyed Hiroshima loosed a nuclear blast equivalent to 12.5 kilotons, or 12,500 tons, of TNT. The Fat Man plutonium bomb dropped on Nagasaki yielded 21 kilotons, or 21,000 tons, of TNT. If the Soviets were going to have spies at Los Alamos, it was most convenient to have them in the sections devising a successful method of implosion.

Klaus Fuchs originally came to the United States at the end of 1943 as a member of a team of fifteen British scientists sent over to help build the bomb. That he made it as far as the Theoretical Division at Los Alamos without arousing anyone’s suspicion was evidence of the nadir of British counterintelligence during the Second World War. The British assured General Groves that none of the fifteen was a security risk. At the time Groves accepted this warranty as genuine, the British government had become a dovecote for Soviet penetration agents. The most outrageous example was the “Cambridge Five,” so dubbed because they had all been recruited while at Cambridge University. Guy Burgess and Donald Maclean were in the Foreign Office. Harold “Kim” Philby, considered so valuable by the Soviets that he was to be awarded the clandestine rank of colonel in the KGB, the successor to the NKVD, was a fast-rising talent in MI6, Britain’s Secret Intelligence Service. John Cairncross was private secretary to Lord Hankey, who in turn was minister without portfolio in Churchill’s War Cabinet, with complete access to its secrets and also responsibility for overseeing British intelligence and chairing the cabinet’s Scientific Advisory Committee. (It was probably Cairncross who passed the Soviets a complete copy of the important feasibility study on the bomb done by British scientists in 1941, the so-called MAUD Committee report.) The fifth was the renowned art historian Sir Anthony Blunt, surveyor of the Queen’s Pictures (keeper of the royal art collection), knighted in 1956 for his services to the Crown, an ardent Marxist and a Soviet spy since he was first enlisted by the NKVD in 1934.

In the case of Fuchs, a simple background check would have disclosed his Communist connections and the peril of placing him in such a sensitive position at Los Alamos. He had entered the Party while a student at the University of Kiel in the early 1930s and openly participated in leading student strikes and other Communist resistance activities against the Nazis until Hitler came to power in 1933. He then had to flee to England via Paris to escape arrest. The family that sponsored him in Bristol had Communist affiliations and so did the professor at Bristol University, a theoretical physicist named Nevill Mott, who gave him an assistantship there. In England, he had also joined a Communist front organization, the Bristol branch of the Society for Cultural Relations with the Soviet Union. When the society staged dramatic readings of the purge trials Stalin was conducting in Moscow to liquidate most of the original Bolshevik leaders on spurious charges, Fuchs would take the part of the prosecutor, the notorious Andrei Vyshinsky. Fuchs subsequently dissembled about his politics, but he had left sufficient tracks for any competent counterintelligence investigator to find. As soon as the British put him to work on preliminary atomic bomb research in Birmingham in 1941, he contacted the Soviet embassy in London and volunteered to spy, turning over copies of all of his research reports.

If Fuchs’s entry into the inner temple at Los Alamos reflected a hardening of the arteries in British counterintelligence, Theodore Hall’s entrance reflected the incompetence of its American counterpart. The times and his background combined to make Ted Hall into a man who betrayed his country out of principle. His original name was Theodore Alvin Holtzberg, born on October 20, 1925, to a Russian Jewish family on Long Island. Until the stock market crashed in 1929 and the Great Depression that followed bankrupted him, Hall’s father, Barney Holtzberg, had prospered sufficiently as a furrier to move the family from an apartment in an immigrant neighborhood in Washington Heights in New York City to a large house in Far Rockaway. With the collapse of the firm, the family moved back to a small apartment in Washington Heights. Barney managed to feed and clothe his family by starting over on a much smaller scale in a niche business in a vastly shrunken fur trade, but the good years and the big home on Long Island were to remain a memory. Adopting the surname of Hall in place of Holtzberg was an idea Ed, eleven years older than his younger brother, came up with. He decided that giving himself an Anglo-Saxon surname would help him evade the widespread anti-Semitism of the period and acquire a job as an engineer. Ted had Ed add him to the court papers and in 1936 he formally became Theodore Alvin Hall.

Left-wing radicalism was common among Russian Jews in the late nineteenth and early twentieth centuries because of the ferociously anti-Semitic policies of Czar Alexander III, a fanatic reactionary who ruled from 1881 to 1894. With the demise of czarism, Fascism became the opposite pole in this ideological universe after its rise, first in Italy in the 1920s under Benito Mussolini, and then with genuine menace under Adolf Hitler in the 1930s in Germany. Ed Hall remembered being attracted by the intense left-wing activity at City College of New York, where tuition was free and where he took his bachelor’s degree in engineering in 1935. He lost interest in politics, however, enlisting in the U.S. Army Air Corps as a private in 1939, after a second degree specializing in chemical engineering and the change of his name to Hall still failed to gain him a civilian engineering job amidst the Great Depression.

Not so his younger brother. Ted Hall was far more affected by the world in which he was growing up, perhaps because he was so much younger and more intellectual than the mechanically minded Ed. It was an apocalyptic world, a world of extremes, of war and revolution, of economic collapse and civil unrest, of mass impoverishment. In Spain the forces of darkness, in the person of General Francisco Franco and his backers, the German and Italian dictators, crushed the life out of the Spanish Republic. At home the capitalist system in which Americans had put their faith appeared profoundly flawed, offering nothing for the future beyond interludes of prosperity followed by repetitive plunges into economic and social misery. Extreme times breed a willingness in some to accept extreme solutions. Ted Hall was one of those people. Despite his high intelligence and his gift for mathematics and science, he was also naive enough and ignorant enough not to understand the barbarous nature of Stalin’s regime. Communism and the Soviet Union seemed to him to offer hope.

When Ted Hall, the sixteen-year-old prodigy, transferred from Queens College to Harvard as a junior in the fall of 1942, of the 3,494 undergraduates at the university, only about a dozen were active members of the John Reed Society, the Communist organization on campus. (Reed, a 1910 Harvard graduate, was the grandson of an Oregon capitalist who made a fortune manufacturing pig iron. He turned radical journalist and wrote an inspired eyewitness account of the Bolshevik Revolution, Ten Days That Shook the World. He died during a typhus epidemic in Russia in 1920 and was buried in the Kremlin wall.) Hall was by chance assigned to room with its chairman and another member and he soon joined. After he and they subsequently moved elsewhere and parted, Hall acquired two new roommates, one of whom was Saville “Savy” Sax, whose Russian Jewish parents had been firm supporters of the Bolshevik Revolution and had passed their Communist convictions on to their son. Although Sax was a literary type with no interest in science (one of his close friends at De Witt Clinton High School in New York had been James Baldwin, who was to become famous as a writer), their shared politics soon made them comrades. When Hall was recruited during his senior year for war work so secret that the recruiter told Hall he could not tell him what it was ahead of time, Sax suggested that if the project turned out to be some superweapon, Hall ought to let the Russians in on it. Hall did not say no.

According to Joseph Albright and Marcia Kunstel, whose book, Bombshell, recounts Ted Hall’s treachery, he arrived at the new laboratory city 7,200 feet above sea level on the Pajarito Plateau in the Jemez Mountains northwest of Santa Fe, New Mexico—the whole of it surrounded by a fence topped by barbed wire and ringed with guard towers—on January 27, 1944, seven months ahead of Fuchs. Again, as with Fuchs, a simple background investigation would have kept him out. But while the Army Counter Intelligence Corps division charged with protecting the security of the Manhattan Project, under the command of Colonel John Lansdale, Jr., strictly controlled entry and exit through the two gates in the fence on either side of the complex, and had agents planted undercover in hotels and bars in Santa Fe and other communities in the area, it did not bother to conduct background checks on inconspicuous types like Hall and many others it allowed inside those gates.

Within less than six months Hall was at the center of the research to perfect the implosion method for the plutonium bomb. He impressed his immediate superior, Bruno Benedetti Rossi, an émigré Italian physicist who headed one of the sections in the experimental physics division, or P Division, under Robert Fox Bacher, the well-known Cornell professor of physics. In July 1944, Hall was therefore designated a team leader for the so-called Ra-La implosion experiments. Ra-La was an abbreviation for radioactive lanthanum, a tracer isotope that emitted intense gamma rays. In the fall of 1943, Rossi and Philip Koontz, a cosmic ray physicist from the University of Colorado, had come up with an idea for a fast-acting radiation counter. It was called a double ionization chamber.

If a capsule of Ra-La was placed in the center of a metal sphere serving as a dummy plutonium core and the sphere was then crushed with a wrapper of conventional explosives, the pattern of the gamma rays given off by the smashed Ra-La would reveal whether the implosion had been sufficiently symmetrical to detonate an actual plutonium core. Hall’s job was to head the team that built the four new ionization chambers normally required for each experiment, as they were destroyed in the explosion, and to rig them to the dummy bomb for the test. Other members of Rossi’s group would move the dummy bomb into place and insert the Ra-La pellet into the sphere. All would then move to a blast shelter where Hall had an oscilloscope, an electronic instrument that records a trace reading on the screen of a cathode-ray tube. When the conventional explosive wrapper was detonated, the ionization chambers would pick up the emission of gamma rays from the pulverized pellet of Ra-La and flash a reading to the screen of the oscilloscope in the moment before they too disintegrated in the blast.

Hall’s assignment enabled him to see a great deal more than the gamma-ray emission reading on the oscilloscope. Prior to each detonation, he was required to calibrate the ionization chambers so that they would give a correct reading. To do this he had to assemble the dummy core in a small shed erected for this purpose. The test cores were exact replicas of the real thing. While in the shed, Hall had plenty of time to note details, for example to measure the size of the core and thus calculate how much plutonium was required for a bomb.

In addition, there was no impediment to Hall obtaining explanations for everything he observed. As a physicist, and thus a member of the scientific staff at Los Alamos, he had been issued a white identity badge the day he arrived. “White badgers” were cleared to read all of the laboratory’s secret technical reports and to attend the weekly colloquia Robert Oppenheimer organized to discuss ongoing work. For security reasons, Groves had wanted at the outset to completely compartmentalize Los Alamos so that a scientist’s knowledge would be limited to the task he had been assigned. Oppenheimer had insisted, however, and correctly as it turned out, that they could not get the bomb built by 1945 unless he was free to run the laboratory as an ongoing seminar in which everyone involved could contribute in solving the problems they were bound to encounter. To meet the deadline, Groves let Oppenheimer have his way. Hall thus had no difficulty in learning the design of the implosion wrapper, or the composition of fast-burning and slow-burning explosives being employed by George Kistiakowsky, the émigré Ukrainian chemist who was the wizard of the Harvard chemistry faculty, to make the wrapper work, or the relative velocity required for the implosion to compress the core to supercriticality.

In mid-October 1944, right after the third and still unsuccessful implosion test, Hall left Los Alamos on a two-week leave. He got in touch with Russian intelligence agents operating out of the Soviet consulate in a posh East Side neighborhood in New York at 7 East 67th Street. The NKVD had an intelligence station, or rezidentura as it was called in Russian, there. Savy Sax helped him. They made the contact through the New York offices of Amtorg, the Soviet import-export organization, and a New York agency that distributed Soviet films. Sax offered to act as the courier who would travel to New Mexico by bus and train to pick up Hall’s reports. Because the mail to and from Los Alamos was censored, the two young men resorted to using Walt Whitman’s famous book of poetry Leaves of Grass for Hall to signal the date, time, and place of the rendezvous. Whitman numbered each of his poems, so it was not difficult for them to set up a book code, one of the oldest forms of encryption. To make certain no one would overhear them, they rented rowboats on the lake in Central Park for discussions to settle these and other important details.

Hall’s motive for committing treason was simple. He believed that his duty did not end with being a good physicist, that he also had an obligation to humanity. His Marxist ideas led him to think that the United States might tumble into another depression after the wartime stimulus to the economy ended with the defeat of Germany and Japan. The social and economic turmoil set off by a renewed economic collapse could bring the triumph of Fascism in America, as it had in Germany. If that happened and a Third World War broke out while the United States still had a monopoly on the bomb, Washington would use it to devastate the Soviet Union. If both nations had the bomb there would be a strategic balance, and thus no nuclear war: both would be afraid of its effects.

Because Fuchs had arrived at Los Alamos but was not yet reporting, the Soviets apparently first learned about the principle of implosion and its implications from a report Hall passed to Sax during a rendezvous in Albuquerque in December 1944. According to David Holloway, the Stanford University political scientist and historian who chronicled the building of the Soviet bomb in a masterly account, Stalin and the Bomb, the information reached Igor Kurchatov, the Soviet physicist who was heading Stalin’s atomic bomb project, in Moscow in March 1945. Implosion was an idea that had not occurred to him, Kurchatov said in his memorandum commenting on the intelligence report, “but the implosion method is undoubtedly of immense interest, is fundamentally correct, and should be subjected to close scrutiny both theoretically and experimentally.”

Hall went right back to the test range on his return to Los Alamos. In three detonations in the first half of February 1945, Rossi’s group, employing special quick-firing electrical detonators devised by the Berkeley physicist and subsequent Nobel Laureate Luis Alvarez, finally got the result they had been seeking. The gamma ray reading on the oscilloscope in the blast shelter showed a symmetrical implosion of the core. At the end of the month, Oppenheimer and Groves and other leading figures at Los Alamos settled on the final design of the plutonium bomb, although they ordered continued Ra-La testing right up until shortly before Trinity on July 16 in order to achieve absolute certainty.

When Sax returned to Harvard in early 1945, Hall acquired a new courier, Lona Petka Cohen, an attractive Polish-American woman, then in her early thirties, who, along with her husband, Morris, was to become a legendary operative in the Soviet secret service. (She died in retirement in Moscow in 1992, Morris three years later.) Her second trip to New Mexico occurred after the Hiroshima and Nagasaki bombings, when the secret of what had been going on at Los Alamos was out and the laboratory had become a much publicized place. The Army Counter Intelligence Corps and the Federal Bureau of Investigation had greatly increased security in the whole area. As soon as Hall passed her his report at a rendezvous on the campus of the University of New Mexico at Albuquerque, she hurried back to a boardinghouse in the New Mexican town of Las Vegas, about eighty miles away, where she had been staying to avoid the attention she might have attracted by putting up at a hotel in Albuquerque or Santa Fe. She stuffed the papers Hall had given her under the top tissues in a box of Kleenex, grabbed her suitcase, and headed for the railroad station.

At the station, she discovered that plainclothes security men were questioning everyone getting on the train and searching their baggage. She waited inside until just before the train was due to depart, then walked up to two agents on the platform next to one of the cars. She put down her suitcase and began to play the helpless female who was late for her train, fumbling at the zipper on the handbag in which she had placed her ticket. Making believe she needed to free her hands to work the zipper, she passed the Kleenex box holding the fruits of Hall’s atomic espionage to one of the agents. After the handbag had been opened, she displayed her ticket and answered the agents’ questions. They searched her bag and suitcase. She then picked up the suitcase and proceeded toward the steps into the car, deliberately leaving the Kleenex box behind with one of the agents. She shrewdly assumed he would think she had forgotten it and be gallant enough to call this to her attention and hand it to her, which is precisely what he did. Back in New York she joked with her NKVD handler from the consulate on East 67th Street that Hall’s report had been “in the hands of the police.”

That Hall’s information, if less detailed, equaled in importance the material from Fuchs was something best understood by the agents at 7 East 67th Street and by their superiors at Moscow Center who were collating it into summary memos for Lavrenti Beria, the chilling figure who was in charge of the NKVD and the archipelago of slave labor camps known as the Gulag, an acronym formed from the initial letters of the Russian words for Main Camp Administration, the bland official term for the camps. Beria was as cruel and as morbidly suspicious as his master, Stalin. He suspected for a long time that American intelligence might be feeding these reports to his agents in New York in order to trick the Soviet Union into wasting prodigious resources trying to build a bomb that was a fantasy. Stalin had initiated a small-scale project to design an atomic bomb in 1943 at the urging of some of the more farsighted Soviet physicists. Igor Kurchatov had been chosen to head it. The choice was a wise one. A well-built, energetic man who was liked by his colleagues, Kurchatov was known as “the Beard,” for the one he grew during the war, or as “Prince Igor,” for his self-confident, take-charge manner. Little in the way of resources had been assigned to the enterprise, however, and it was more in the nature of a research group than an organization to build a bomb. Other, not so farsighted Soviet physicists were saying it was impossible to create such a bomb or that it was something far off in the future. Had the amateurish and frequently incompetent reports from David Greenglass, the Army machinist who ground sections of high-explosive cast into solid forms called lenses for the plutonium wrapper, been the only touchstone against which to compare the materials from Fuchs, the suspicion of Beria, and in turn that of Stalin, would have been that much greater and the agents in New York and those in Moscow doing the collating might have been more hesitant about passing on the fruits of the espionage. They knew that if they were being hoodwinked, their lives would be forfeited. Beria had said to one of his senior intelligence officers as he was being handed a report: “If this is disinformation, I’ll put you all in the cellar.” The cellar of the Lubyanka Prison was one of the places where torture and executions took place. Ted Hall made the difference. His was the sophisticated spying of another physicist and Fuchs’s information checked out against his.

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