Editing Soviet atomic bomb project (section)

===Soviet intelligence management in the Manhattan Project===
{{Main|History of Soviet and Russian espionage in the United States|History of Soviet espionage}}
In 1945, the Soviet intelligence obtained rough blueprints of the first U.S. atomic device.<ref>{{Cite web| title=The Russian-A(merican) Bomb: The Role of Espionage in the Soviet Atomic Bomb Project| url=http://www.hcs.harvard.edu/~jus/0302/schwartz.pdf|archiveurl=https://web.archive.org/web/20191029164858/http://www.hcs.harvard.edu/~jus/0302/schwartz.pdf|url-status=dead|archivedate=October 29, 2019|website=www.hcs.harvard.edu}}</ref><ref>The Rise and Fall of the Soviet Union
 by Martin Mccauley</ref>{{full citation needed|date=February 2025}} Alexei Kojevnikov has estimated that the primary way in which the espionage may have sped up the Soviet project was that it allowed Khariton to avoid dangerous tests to determine the size of the critical mass.{{Sfn|Kojevnikov|2004}} These tests in the U.S., known as "tickling the dragon's tail", consumed a good deal of time and claimed at least two lives; see [[Harry Daghlian]] and [[Louis Slotin]].

The published [[Smyth Report]] of 1945 on the Manhattan Project was translated into Russian, and the translators noted that a sentence on the effect of "poisoning" of Plutonium-239 in the first (lithograph) edition had been deleted from the next (Princeton) edition by [[Leslie Groves|Groves]]. This change was noted by the Russian translators, and alerted the Soviet Union to the problem (which had meant that reactor-bred plutonium could not be used in a simple gun-type bomb like the proposed [[Thin Man (nuclear bomb)|Thin Man]]).

One of the key pieces of information, which Soviet intelligence obtained from Fuchs, was a cross-section for [[Nuclear fusion|D-T fusion]]. This data was available to top Soviet officials roughly three years before it was openly published in the ''Physical Review'' in 1949. However, this data was not forwarded to [[Vitaly Ginzburg]] or [[Andrei Sakharov]] until very late, practically months before publication.{{Citation needed|date=March 2013}} Initially both Ginzburg and Sakharov estimated such a cross-section to be similar to the D-D reaction. Once the actual cross-section become known to Ginzburg and Sakharov, the Sloika design become a priority, which resulted in a successful test in 1953.

Comparing the timelines of H-bomb development, some researchers{{Who|date=August 2023}} came to the conclusion that the Soviets had a gap in access to classified information regarding the H-bomb at least between late 1950 and some time in 1953. Earlier, e.g., in 1948, Fuchs gave the Soviets a detailed update of the classical super<ref>{{cite web |title=The Classical Super is Born |url=https://www.atomicarchive.com/history/hydrogen-bomb/page-3.html |website=atomicarchive.com: Exploring the History, Science, and Consequences of the Atomic Bomb |publisher=AJ Software & Multimedia. |access-date=21 July 2023}}</ref> progress, including an idea to use lithium, but did not explain it was specifically lithium-6. By 1951 Teller accepted the fact that the "classical super" scheme wasn't feasible, following results obtained by various researchers (including [[Stanislaw Ulam]]) and calculations performed by [[John von Neumann]] in late 1950.

Yet the research for the Soviet analogue of "classical super" continued until December 1953, when the researchers were reallocated to a new project working on what later became a true H-bomb design, based on radiation implosion. This remains an open topic for research, whether the Soviet intelligence was able to obtain any specific data on Teller–Ulam design in 1953 or early 1954. Yet, Soviet officials directed the scientists to work on a new scheme, and the entire process took less than two years, commencing around January 1954 and producing a successful test in November 1955. It also took just several months before the idea of radiation implosion was conceived, and there is no documented evidence claiming priority. It is also possible that Soviets were able to obtain a document lost by [[John Archibald Wheeler|John Wheeler]] on a train in 1953, which reportedly contained key information about thermonuclear weapon design.