"Atomic spies" and "Atom spies" are terms that refer to various people in the United States, Great Britain, and Canada who are thought to have illicitly given information about nuclear weapons production or design to the Soviet Union during World War II and the early Cold War. Exactly what was given, and whether everyone on the list gave it, is still a matter of some scholarly dispute, and in some cases what were originally seen as strong testimonies or confessions were admitted as fabricated in later years. Their work constitutes the most publicly well-known and well-documented case of nuclear espionage in the history of nuclear weapons. There was a movement among nuclear scientists to share the information with the world scientific community, but that was firmly quashed by the U.S. government.
The modern day sharing of nuclear technology with Iran, Libya, North Korea and possibly other regimes on the part of Abdul Qadeer Khan has yet to be fully explored. It is an open question whether the term "atom spy" will be applied to those operating outside the Cold War period, such as Khan and Argentine-American physicist Leonardo Mascheroni.
Whether the information significantly aided the speed of the Soviet atomic bomb project is also disputed. While some of the information given could have aided in developing a nuclear weapon, the manner in which the heads of the Soviet bomb project actually used the information has led scholars to doubt its role in increasing the speed of development. According to this account, Igor Kurchatov and Lavrenty Beria used the information primarily as a "check" against their own scientists' work and did not liberally share the information with them, distrusting both their own scientists as well as the espionage information. Later scholarship has also shown that the decisive brake on early Soviet development was not problems in weapons design but, as in the Manhattan Project, the difficulty in procuring fissile materials, especially since the Soviet Union had no uranium deposits known when it began its program (unlike the United States).
Confirmation about espionage work came from the VENONA project, which intercepted and decrypted Soviet intelligence reports sent during and after World War II. These provided clues to the identity of several spies at Los Alamos and elsewhere, some of whom have never been identified. Some of this information was available, but not usable in court for secrecy reasons, during the trials of the 1950s. As well records from Soviet archives, which were briefly opened to researchers after the fall of the Soviet Union, included more information about some spies.
Importance of atomic spies 
Before the beginning of World War II, the theoretical possibility for nuclear fission was a highly discussed topic among the top physicists in the world. Scientists from the Soviet Union were later recognized for their contributions to the understanding of a nuclear reality, and were awarded several Nobel Prizes. Igor Kurchatov, L. D. Landau, Kirill Sinelnikov, were among those Soviet Scientists that helped establish, and prove the existence of a splittable atom. Dwarfed by, and lost upon the scale of the Manhattan Project, the significance of the contributions are rarely understood, and credited, outside of the field of physics. According to several sources, it was understood on a theoretical level that the atom provided for extremely powerful and novel releases of energy, and could possibly be utilized in the future for military purposes. In recorded comments made by the physicists themselves, they lamented over their inability to achieve any kind of practical application from the discoveries. This would show that the scientists thought the creation of an atomic weapon was a pipe-dream, and untenable. Although they could conceivably have been first to generate a man-made fission reaction, in reality they lacked the ambition, the funding, the engineering capability, the leadership, and ultimately, the capability to do so. The undertaking would be of an unimaginable scale, and the resources required to engineer for such use as a nuclear bomb, and nuclear power were deemed too great to pursue.
The United States, in collaboration with the British and Canada, correctly recognized the significance of an atomic bomb at the urging of Albert Einstein and Leo Szilard, and immediately embarked upon a race to acquire a usable device. During the quest to create the atomic bomb it is estimated that $2 billion dollars, eighty-six thousand tons of silver, and twenty-four thousand skilled workers drove the research and development phase of the project. Those skilled workers included the people to maintain and operate the machinery necessary for research. The largest allied facility had five hundred scientists working on the project as well as a team of fifty to derive the equations for the cascade of neutrons required to drive the reaction. The state of a fledgling Soviet program was quite different, and the program consisted of fifty scientists, and a mere two mathematicians trying to work out the equations for the particle cascade. The research and development of techniques to produce sufficiently enriched uranium and plutonium were beyond the scope and efforts of the team. The knowledge of techniques and strategies that were being employed in the Allied programs that the Soviet Union procured intelligence on by means of espionage played a significant role in the rapid development of the Soviet bomb after the war.
The research and development of methods suitable for doping and separating the highly reactive isotopes needed to create the pay load for a nuclear warhead took years, and consumed vast amount of resources. The allies of the United States and Great Britain dedicated their best scientists to this cause and constructed three plants each with a different isotope extraction method. The allied program decided to use a gas phase extraction to obtain the pure uranium necessary for an atomic detonation. To find this method it took large quantities of uranium ore and other rare materials such as graphite to successfully purify the U-235 isotope. The quantities required for the development were also beyond the scope and purview of the Soviet program.
The Soviet Union did not even have natural uranium ore mines at the start of the nuclear arms race. A lack of materials made it very difficult to conduct novel research, and map out a clear pathway to achieving the fuel they needed. Efforts to produce Uranium fuel dirt cheap only frustrated Soviet efforts, and they found their industrial techniques for refinement lacking. The problem was eventually rectified through the use of information stolen from the Manhattan Project. Without such, the problems the Soviet atomic team experienced would have taken many, many years to correct, effecting the end date of a Soviet atomic weapon significantly.
The missing element that explains the great leaps in the Soviets Union's atomic program is the espionage information and technical data Moscow was able to obtain from the Manhattan Project. Upon the realization of the American plans to develop an atomic bomb during the 1930s, Moscow began actively seeking agents to get information. Moscow was very specific in asking for information from their intelligence cells in America and demanded updates on the progress of the allied project. Moscow was also greatly concerned with the procedures being used for U-235 separation, what method of detonation was being used, and what industrial equipment was being used for these techniques.
To obtain this information from the Manhattan Project, the Soviet Union needed spies that, first of all, had security clearance high enough to have access to classified information, and secondly, could understand and interpret what they were stealing. Moscow also needed reliable spies who believed in the communist cause and would provide accurate information. One such Soviet spy was Theodore Hall, who had been a developer on the bombs dropped in Japan. Hall gave up the specifications of the bomb dropped on Nagasaki. This information allowed the Soviet scientists a firsthand look at the successful set up of an atomic weapon built by the Allied team.
Although Hall's information was helpful to the cause, the most influential of the atomic spies was Klaus Fuchs. Klaus was a German-born British physicist who was sent to America to work on the atomic project where he became one of the lead scientists. Klaus became a member of the Communist Party while he was still a student in Germany. At the onset of World War II, Klaus fled to Great Britain to escape the fighting, where he became one of the lead nuclear physicists in the British program and was later sent to collaborate on the Manhattan Project. Due to Fuchs's position in the atomic program, he had access to most, if not all, of the material Moscow desired. Klaus was also able to interpret and understand the information he was stealing, which made him an invaluable resource. Klaus provided the Soviets with detailed information on the gas phase separation process. He also provided specifications for the pay load, calculations and relationships for setting of the fission reaction, and schematics for labs producing weapons grade isotopes. This information helped the smaller under-manned and under-supplied Soviet scientists with a hard push in the direction of the successful detonation of a nuclear weapon.
The Soviet nuclear program would have eventually been able to develop a nuclear weapon without the aid of espionage. But a basic understanding of the usefulness of an atomic weapon, the sheer resources, and the talent weren't present until much, much later. The information passed helped the Soviet scientists identify which methods worked and prevented wasting valuable resources on techniques proven ineffective in the development of the American bomb. The speed at which the Soviet nuclear program achieved a working bomb with so few resources was driven by the amount of information acquired through espionage. In terms of its effect on mankind, and the shaping of a state, it was one of the most significant intelligence coups in the history of man.
Notable atomic spies 
- Morris Cohen – American, "Thanks to Cohen, designers of the Soviet atomic bomb got piles of technical documentation straight from the secret laboratory in Los Alamos," the newspaper Komsomolskaya Pravda said. Morris and his wife, Lona, served eight years in prison, less than half of their sentences before being released in a prisoner swap with The Soviet Union. He died without revealing the name of the American scientist who helped pass vital information about the United States atomic bomb project.
- Klaus Fuchs – German-born British theoretical physicist who worked with the British delegation at Los Alamos during the Manhattan Project. After Fuchs' confession there was a trial that lasted less than 90 minutes, Lord Goddard sentenced him to fourteen years' imprisonment, the maximum for violating the Official Secrets Act. He escaped the charge of espionage because of the lack of independent evidence and because, at the time of the crime, the Soviet Union was not an enemy of Great Britain. In December 1950 he was stripped of his British citizenship. He was released on June 23, 1959, after serving nine years and four months of his sentence at Wakefield prison. He was allowed to emigrate to Dresden, then in the German Democratic Republic.
- Harry Gold – American, confessed to acting as a courier for Greenglass and Fuchs. He was sentenced in 1951 to thirty years imprisonment. He was paroled in May 1966, after serving just over half of his sentence.
- David Greenglass – an American machinist at Los Alamos during the Manhattan Project. Greenglass confessed that he gave crude schematics of lab experiments to the Russians during World War II. Some aspects of his testimony against his sister and brother-in-law (the Rosenbergs, see below) are now thought to have been fabricated in an effort to keep his own wife, Ruth, from prosecution. Greenglass was sentenced to 15 years in prison, served 10 years, and later reunited with his wife.
- Theodore Hall – a young American physicist at Los Alamos, whose identity as a spy was not revealed until very late in the 20th century. He was never tried for his espionage work, though he seems to have admitted to it in later years to reporters and to his family.
- George Koval – The American born son of a Belorussian emigrant family that returned to the Soviet Union where he was inducted into the Red Army and recruited into the GRU intelligence service. He infiltrated the US Army and became a radiation health officer in the Special Engineering Detachment. Acting under the code name DELMAR he obtained information from Oak Ridge and the Dayton Project about the Urchin (detonator) used on the Fat Man plutonium bomb. His work was not known to the west until he was posthumously recognized as a hero of the Russian Federation by Vladimir Putin in 2007.
- Irving Lerner – An American film director, he was caught photographing the cyclotron at the University of California, Berkeley in 1944. After the war he was blacklisted.
- Allan Nunn May – A British citizen, he was one of the first Soviet spies uncovered during the cold war. He worked on the Manhattan Project and was betrayed by a Soviet defector in Canada. His was uncovered in 1946 and it led the United States to restrict the sharing of atomic secrets with Britain. On May 1, 1946, he was sentenced to ten years hard labour. He was released in 1952, after serving six and a half years.
- Ethel and Julius Rosenberg – Americans who were involved in coordinating and recruiting an espionage network that included Ethel's brother, David Greenglass. Julius and Ethel Rosenberg were tried for conspiracy to commit espionage, since the prosecution seemed to feel that there was not enough evidence to convict on espionage. Treason charges were not applicable, since the United States and the Soviet Union were allies at the time. The Rosenbergs denied all the charges but were convicted in a trial in which the prosecutor Roy Cohn said he was in daily secret contact with the judge, Irving Kaufman. Despite an international movement demanding clemency, and appeals to President Dwight D. Eisenhower by leading European intellectuals and the Pope, the Rosenbergs were executed at the height of the Korean War. President Eisenhower wrote to his son, serving in Korea, that if he spared Ethel (presumably for the sake of her children), then the Soviets would simply recruit their spies from among women.
- Morton Sobell – American engineer tried and convicted along with the Rosenbergs, was sentenced to 30 years imprisonment but released from Alcatraz in 1969, after serving 17 years and 9 months. After proclaiming his innocence for over half a century, Sobell admitted spying for the Soviets, and implicated Julius Rosenberg, in an interview with the New York Times published on September 11, 2008.
- Schwartz, Micheal. The Russian-A(merican) Bomb: The Role of Espionage in the Soviet Atomic Bomb Project. J. Undergrad. Sci. 3: 103-108 (Summer 1996) http://www.hcs.harvard.edu/~jus/0302/schwartz.pdf
- Joint Committee on Atomic Energy. Soviet Atomic Espionage. Chapters 2-3 United States Government Printing Office, Washington 1951. http://archive.org/stream/sovietatomicespi1951unit#page/n3/mode/2up
- Schwartz, Micheal. Russian Bomb 103-08
- Schwartz, Micheal. Russian Bomb 103-08f
- Allen Weinstein and Alexander Vassiliev, "Atomic Espionage: from Fuchs to the Rosenburgs" in The Haunted Wood, (New York: Random House Inc, 1999), 172-222.
- Weinstein and Vassiliev,Atomic Espionage, 180-85
- Weinstein and Vassiliev,Atomic Espionage,190-200
- Weinstein and Vassiliev,Atomic Espionage,180
- Holmes,Marian. "Spies Who Spilled Atomic Bomb Secrets". Smithsonian.com,April 20, 2009. http://www.smithsonianmag.com/history-archaeology/Spies-Who-Spilled-Atomic-Bomb-Secrets.html
- Holmes,Spies Who Spilled,1-2
- Weinstein and Vassiliev, Atomic Espionage,200-10
- Joint Committee Chapter 2
- "Morris Cohen, 84, Soviet Spy Who Passed Atom Plans in 40's". New York Times. 5 July 1995. Retrieved 2008-07-07. "Morris Cohen, an American who spied for the Soviet Union and was instrumental in relaying atomic bomb secrets to the Kremlin in the 1940s, has died, Russian newspapers reported today. Mr. Cohen, best known in the West as Peter Kroger, died of heart failure in a Moscow hospital on June 23 at age 84, according to news reports."
- A.M. Hornblum, 'The Invisible Harry Gold' (Yale University Press, 2010) kindle edition. locations 4030-37
- Pace, Eric (January 29, 1988). "Klaus Fuchs, Physicist Who Gave Atom Secrets to Soviet, Dies at 76". New York Times. Retrieved 2008-07-07. "Klaus Fuchs, the German-born physicist who was imprisoned in the 1950s in Britain after being convicted of passing nuclear secrets to the Soviet Union, died yesterday, the East German press agency A.D.N. reported. He was 76 years old."
- "Klaus Fuchs". TruTV. Retrieved 2008-07-07. "His name was Klaus Emil Fuchs, and he was, as it has been shown by history, the most important atom spy in history. Not any of the notorious names in the saga of the theft of the atom bomb secrets Allan Nunn May, Julius and Ethel Rosenberg, and David Greenglass had been as important to the Russian effort as Klaus Fuchs."
- "1972 Death of Harry Gold Revealed". New York Times. February 14, 1974. Retrieved 2008-07-07. "Harry Gold, who served 15 years in Federal prison as a confessed atomic spy courier, for Klaus Fuchs, a Soviet agent, and who was a key Government witness in the Julius and Ethel Rosenberg espionage case in 1951, died 18 months ago in Philadelphia."
- "Greenglass, in Prison, Vows to Kin He Told Truth About Rosenbergs". New York Times. March 19, 1953. Retrieved 2008-07-07. "David Greenglass, serving fifteen years as a confessed atom spy, denied to members of his family recently that he had been coached by the Federal Bureau of Investigation in the drawing of segments of the atom bomb, or that he had given perjured testimony against his sister, Mrs. Ethel Rosenberg, and her husband, Julius."
- Cowell, Alan (November 10, 1999). "Theodore Hall, Prodigy and Atomic Spy, Dies at 74". New York Times. Retrieved 2008-06-26. "Theodore Alvin Hall, who was the youngest physicist to work on the atomic bomb project at Los Alamos during World War II and was later identified as a Soviet spy, died on Nov. 1 in Cambridge, England, where he had become a leading, if diffident, pioneer in biological research. He was 74. ... Mr. Albright and Ms. Kunstel say Mr. Hall and a former Harvard roommate, Saville Sax, approached a Soviet trade company in New York in late 1944 and began supplying critical information about the atomic project."
- "Alan Nunn May, 91, Pioneer In Atomic Spying for Soviets". New York Times. 25 January 2003. Retrieved 2008-07-07. "Alan Nunn May, a British atomic scientist who spied for the Soviet Union, died on Jan. 12 in Cambridge. He was 91. ... One of the first Soviet spies uncovered during the cold war, Dr. Nunn May worked on the Manhattan Project and was betrayed by a Soviet defector in Canada. His unmasking in 1946 led the United States to restrict the sharing of atomic secrets with Britain."
- "Execution of the Rosenbergs". London: The Guardian. June 20, 1953. Retrieved 2008-06-24. "Julius and Ethel Rosenberg were executed early this morning at Sing Sing Prison for conspiring to pass atomic secrets to Russia in World War II."
- "The Rosenbergs: A Case of Love, Espionage, Deceit and Betray". TruTV. Retrieved 2008-07-07. "Julius and Ethel Rosenberg were charged with the crime of conspiracy to commit espionage, and tried under the Espionage Act of 1917."
- "Execution of the Rosenbergs". The Guardian (London). June 20, 1953. Retrieved 2008-06-24. "Julius and Ethel Rosenberg were executed early this morning at Sing Sing Prison for conspiring to pass atomic secrets to Russia in World War II."
- "Morton Sobell Free As Spy Term Ends". New York Times. January 15, 1969. Retrieved 2008-07-07. "Morton Sobell, sentenced to 30 years for a wartime espionage conspiracy to deliver vital national secrets to the Soviet Union, was released from prison yesterday after serving 17 years and 9 months."
- Roberts, Sam (September 11, 2008). "For First Time, Figure in Rosenberg Case Admits Spying for Soviets". New York Times. Archived from the original on 12 September 2008. Retrieved 2008-09-11. "In an interview on Thursday, Mr. Sobell, who served nearly 19 years in Alcatraz and other federal prisons, admitted for the first time that he had been a Soviet spy."
Further reading 
- Alexei Kojevnikov, Stalin's Great Science: The Times and Adventures of Soviet Physicists (Imperial College Press, 2004). ISBN 1-86094-420-5 (use of espionage data by Soviets)
- Gregg Herken, Brotherhood of the Bomb: The Tangled Lives and Loyalties of Robert Oppenheimer, Ernest Lawrence, and Edward Teller (New York: Henry Holt and Co., 2002). ISBN 0-8050-6588-1 (details on Fuchs)
- Richard Rhodes, Dark Sun: The Making of the Hydrogen Bomb (New York: Simon and Schuster, 1995). ISBN 0-684-80400-X (general overview of Fuchs and Rosenberg cases)