Aldrich Ames in CIA and Robert Hanssen in FBI, though they worked much later and neither was a communist (Hanssen might be or at least antiimperialist, but he never admitted that). Hanssen pissed the pigs so much they given him 15 life sentences.
In the Manhattan project, beside Rosenbergs there were at least three other Soviet spies:
Georg Koval, an engineer working for GRU, most likely real communist, USA do not know till today what exactly he gave to GRU and the fact he was a spy was only really revealed in 2007 when Putin gave him the Hero of Russian Federation for that.
Harry Gold, courier, he was a communist but apparently very shallow one. Recruited by NKVD he was only a minor asset. Didn’t worked in MP directly, but was courier for Fuchs.
Klaus Fuchs, physicist, one of the main theoretical fathers of both nuclear and hydrogen bombs, passed tons of info about US, UK and Canadian nuclear projects to Soviets over the 9 years. He was at first member of SPD, from which he was kicked out for associating with Thalmann, then he joined KPD. Later in life he lived in GDR and was a member of cnetral comitee of SED, so definitely real deal communist.
All that said, it is actually still unknown and most likely exaggerated how much all those agents improved the Soviet nuclear project, most likely the data they provided served mostly to compare with western projects because Soviet nuclear project had no real problems with theory or engineering, they were mostly restricted by the amount of enriched uranium and plutonium they could produce because in the first piles it went really slow, and USA had significant time advantage in that.
Even the wiki on the Rosenbergs backs up the idea that the spying likely didn’t accelerate development that much of at all
Lavrentiy Beria, the head official of the Soviet nuclear project, used foreign intelligence only as a third-party check rather than giving it directly to the design teams, who he did not clear to know about the espionage efforts, and the development was indigenous. Considering that the pace of the Soviet program was set primarily by the amount of uranium that it could procure, it is difficult for scholars to judge accurately how much time was saved, if any.
Like basically everywhere else, the major limiting factor was access to uranium. Not technical knowledge.
Aldrich Ames in CIA and Robert Hanssen in FBI, though they worked much later and neither was a communist (Hanssen might be or at least antiimperialist, but he never admitted that). Hanssen pissed the pigs so much they given him 15 life sentences.
In the Manhattan project, beside Rosenbergs there were at least three other Soviet spies:
All that said, it is actually still unknown and most likely exaggerated how much all those agents improved the Soviet nuclear project, most likely the data they provided served mostly to compare with western projects because Soviet nuclear project had no real problems with theory or engineering, they were mostly restricted by the amount of enriched uranium and plutonium they could produce because in the first piles it went really slow, and USA had significant time advantage in that.
Even the wiki on the Rosenbergs backs up the idea that the spying likely didn’t accelerate development that much of at all
Like basically everywhere else, the major limiting factor was access to uranium. Not technical knowledge.