Pash’s plan to abduct and interrogate Berkeley physicists

Boris Pash’s plan to abduct and interrogate Berkeley physicists grew from an intelligence investigation in which suspicion rapidly outran proof. After a tapped conversation linked Steve Nelson to an unidentified contact called Joe, Pash interpreted the transcript as evidence of espionage and as confirmation of his suspicions about J. Robert Oppenheimer. His investigators then focused on young physicists connected to the Berkeley laboratory. In July 1943, the FBI reported that Pash wanted four of them taken by boat out to sea and questioned by force. The plan was not carried out: the FBI pressed to stop it, recognizing that the proposed interrogation would produce evidence that could not be used in court and that Pash apparently did not intend to leave anyone available for prosecution.

From an intercepted conversation to a Berkeley investigation

An FBI transcript of Nelson’s conversation with the still-unidentified “Joe” was delivered to Pash, the Manhattan Project’s chief counterintelligence officer. Pash had spent much of his career pursuing communists and regarded the Soviet Union as America’s mortal enemy, not simply a wartime ally. He quickly concluded that the transcript showed espionage and validated his suspicions about Oppenheimer. The transcript could not be used to charge Nelson or the unknown Joe because the wiretap was illegal. Authorities could, however, use its information to trace Nelson’s contacts, and Pash was authorized to investigate whether the Berkeley laboratory was a target of espionage.

Pash later testified that investigators knew Joe had furnished Nelson with technical information and timetables relating to the bomb project. The account records what Pash and his colleagues believed; it does not establish that the unidentified contact had in fact supplied those materials. That distinction mattered as the inquiry moved from an intercepted conversation to surveillance of people whose political associations and personal contacts were treated as evidence of a larger conspiracy.

The photograph and the suspects

The investigation initially centered on Giovanni Rossi Lomanitz, not because the evidence connected him directly to the unidentified Joe, but because Pash had information that Lomanitz belonged to the Communist Party. Investigators followed him. In June 1943, just outside Sather Gate at the University of California, Berkeley, he posed for a photograph with several friends, their arms draped over one another’s shoulders. After the group dispersed, a government agent bought the negative from the campus photographer.

The men in the photograph were identified as Joseph Weinberg, David Bohm, and Max Friedman, all students of Oppenheimer. The image did not document an exchange of secrets; it showed the young men together. Yet from that point, they were marked as subversives. Pash testified that his investigators had found the four men together frequently. He said that, by studying the photograph and their associations, they had identified the previously unknown Joe as Joseph Weinberg, and that they had sufficient information to name Weinberg and Bohm as Communist Party members. The sequence reveals how an ordinary campus photograph became an instrument of identification: its evidentiary weight came not from what it showed about espionage, but from the network of suspicion investigators built around it.

The proposed abduction

Pash became convinced that he had uncovered a sophisticated ring of Soviet agents and believed that extraordinary methods were justified to break the suspects. In July, the FBI’s San Francisco field office reported that he wanted Lomanitz, Weinberg, Bohm, and Friedman kidnapped, taken out to sea in a boat, and interrogated “after the Russian manner.” The setting was integral to the proposal. Removed from ordinary legal safeguards and taken offshore, the four men would be questioned in circumstances designed to compel information rather than preserve a case for public trial.

The FBI recognized the legal and practical consequences. Any information obtained through such questioning could not be used in court. Its report also observed that Pash apparently did not intend to have anyone available for prosecution after the interrogation. The FBI considered the proposed operation unacceptable and brought pressure to bear to discourage it. The evidence establishes a proposed abduction and an effort to prevent it, not that the four physicists were actually taken to sea or interrogated under this plan.

Surveillance, inference, and wartime security

The contemplated abduction belonged to a wider pattern of surveillance around Nelson and the Berkeley laboratory. The FBI had placed a microphone in Nelson’s office before bugging his home. Conversations captured by the office microphone suggested that he had methodically gathered information about the laboratory from young physicists sympathetic to the Soviet war effort. In one recorded conversation from October 1942, Young Communist League organizer Lloyd Lehmann, who also worked at the laboratory, told Nelson that an important weapon was under development and that he was involved in the research. Nelson asked whether Oppenheimer knew Lehmann was a league member, described Oppenheimer as “too jittery,” and said that Oppenheimer had once been active in the Party but was then inactive. He also remarked that the government left Oppenheimer alone because of his scientific ability, and referred to Oppenheimer’s past political work.

Those intercepted remarks help explain the investigative atmosphere, but they do not by themselves demonstrate the allegations Pash attached to the Berkeley physicists. In the inquiry, past political associations, proximity, and a photograph of friends together fed an increasingly expansive suspicion of espionage. The proposed kidnapping marked its most coercive point: rather than wait for evidence that could sustain prosecution, Pash sought to obtain information through an interrogation the FBI judged legally unusable. The bureau’s intervention stopped that particular plan, while the episode exposed how wartime counterintelligence could turn surveillance and inference into a threat to the people under investigation.