In a two-part column in Asimov's Science Fiction Magazine, Robert Silverberg tells the incredible story of the Cleve Cartmill affair: in 1944, John W Campbell published a story by the writer Cleve Cartmill that laid out an eeriy accurate depiction of how the atom bomb would work, prompting a panicked -- and sometimes comical -- intelligence investigation into a putative conspiracy of science fiction writers:
Campbell provided the Military Intelligence man with Cartmill’s address–in Manhattan Beach, California. The link to the top-secret Manhattan Project based in Los Alamos was too obvious to overlook. Riley sent word to the California branch office of Intelligence that Cartmill should be placed under immediate surveillance; plainly he knew too much about our hush-hush A-bomb research. Who had tipped him off ? Both Cartmill and Campbell would need further watching.
And before long it began to seem as though a whole network of science fiction writers might be involved–a chain of conspirators. For example, the report continues, "It is established that Cartmill is very friendly with [ ], Retired U.S.N.R., who is associated with [ ] at the Philadelphia Navy Yard. This [ ] formerly was doing research work at Columbia University, and he is said to have accepted some material thought to be atomic copper from [ ] in order to measure it in the mass spectroscope at Columbia University. [ ] was advised by [ ] that the device was broken. He never received the material back from [ ]. One [ ] who has written for [ ] Magazine is said to be working with [ ] also. The possibility of the transmittal through [ ] to Cartmill has not so far been resolved. . . ."
Well, now it can be told, and you are quite familiar with the names of these sinister people. The retired naval man was Robert A. Heinlein. His Philadelphia Navy Yard associate, the former Columbia man, was Isaac Asimov. The one who sent the copper to Asimov and never got it back was Will F. Jenkins, who wrote science fiction under the pseudonym of Murray Leinster. The blanked-out magazine was Astounding, and the other writer working at the Navy Yard with Heinlein and Asimov was L. Sprague de Camp.
(via Making Light)
See also: Pulp SF magazine's role in atom bomb