Oppenheimer's 1943 interrogation by Boris Pash turned a warning about a possible attempt to obtain scientific information for the Soviet Union into a secret record that would haunt Oppenheimer years later. He named George C. Eltenton, but refused to identify the friend who had relayed Eltenton’s proposal or the other scientists he said had been approached. The interview exposed the strain between Oppenheimer’s sympathy for an embattled wartime ally and his insistence that secret information should not pass through unofficial channels; it also created a consequential documentary record of claims he would later describe as fabricated.

From warning to interrogation

Oppenheimer’s meeting with Pash followed a series of warnings about Eltenton. In August 1943, Oppenheimer first raised Eltenton’s name with Leslie Groves, then, on August 25, visited Lieutenant Lyall Johnson, the Army security officer at the Berkeley Radiation Laboratory. Oppenheimer said Eltenton, an employee of Shell Development Company who was active in FAECT, should be watched because he might be trying to obtain information about the laboratory’s work. Johnson called his superior, Colonel Pash, who directed him to bring Oppenheimer back the next day. Overnight, security officers concealed a microphone in the base of the telephone on Johnson’s desk and connected it to a recording device in an adjoining room.

When Oppenheimer returned, he was surprised to find Pash there. The security officer was still a stranger to him, though Oppenheimer knew his reputation. Pash took charge of the questioning. Oppenheimer initially tried to discuss Giovanni Rossi Lomanitz, whose position at the laboratory had become a concern to him. He wanted to tell Lomanitz that he had been indiscreet. Pash instead steered the conversation toward what he considered the more serious question: whether other groups were interested in the laboratory.

The account Oppenheimer gave

Oppenheimer said he had no firsthand knowledge of such groups, but described an indirect approach involving a person attached to the Soviet consulate. According to his account, an intermediary had indicated that information could be passed to Soviet representatives without a leak or scandal. Oppenheimer said he could understand arguments for the Commander in Chief informing the Russians that the United States was working on the problem. What troubled him was the prospect of information being moved “out the back door.” His distinction was between an official decision to share information with an ally and an unofficial attempt to pass it secretly.

He identified Eltenton as someone who should be watched, saying Eltenton had probably been asked to provide information. But when Pash pressed him to name those who had been approached, Oppenheimer refused. He said he knew of two or three cases, including two men then at Los Alamos and a third man from the Berkeley laboratory who had left, or was expected to transfer, to Site X, the Manhattan Project facility at Oak Ridge. He described a third party, a member of the Berkeley faculty, as the link between Eltenton and the scientists, but would not identify him either. Oppenheimer insisted that the intermediary and the scientists were innocent, and said naming the intermediary would be a mistake.

To explain how the proposal had been presented, Oppenheimer described the wartime anxiety of people who wanted the Soviet Union, then an ally fighting fascism, to know more about the work. Their attitude, he said, was one of “bewilderment rather than one of cooperation”: they were troubled by the possibility of helping an ally through unofficial channels, not simply offering to do so. He set the episode against concern that official communication between the allies was inadequate and that the Soviets were bearing the brunt of the fight against fascism. Yet he maintained that Eltenton’s activities merited attention. His account thus combined an explanation of the proposal’s sympathetic political setting with a firm rejection of secret, unofficial transmission.

Security, loyalty, and the recording

Oppenheimer also drew the conversation back to FAECT. He thought the union’s activities deserved watching and suggested that an informant in its local might observe what was happening. When Pash asked whether Oppenheimer knew anyone who might serve, Oppenheimer said he did not; he had only heard that David Fox was its president. The episode connected his suspicion about possible espionage with his concern over union organizing, even though he did not present the union itself as proof of an intelligence operation.

As director of Los Alamos, Oppenheimer assured Pash that security there was entirely in order. He said he would be willing to be shot if he had done anything wrong. The interview ended cordially, but the exchange had left behind a peculiar record: Oppenheimer had identified Eltenton, described an unnamed intermediary and several unnamed scientists, and asserted that all were innocent without providing the names Pash sought. The book characterizes this performance as bizarre and ultimately disastrous—not because the interview established that the unnamed people were spies, but because it preserved Oppenheimer’s confident yet unverifiable account.

Oppenheimer did not know that the conversation had been recorded. The transcript entered his security file, where it preserved both his words and the uncertainty surrounding them. Years later, he said that the account of several approaches had been a fabricated “cock and bull” story devised to protect the identity of his friend Haakon Chevalier. The later explanation left a damaging contradiction: either Oppenheimer had embellished his account to Pash, or the account he gave in 1943 was closer to the truth than his later version. The evidence does not resolve which explanation is correct.

The long aftermath

The recorded interview became a delayed liability. In 1943, its detailed account could be read as an attempt to alert security officers while shielding people Oppenheimer believed innocent. Later, however, Oppenheimer’s admission that he had invented part of the story gave his antagonists a basis to challenge his credibility. The contradiction resurfaced in the 1954 security hearing, where the competing versions could be used against him. As the book puts it, Oppenheimer had unknowingly swallowed a time bomb: nearly a decade separated the interview from the hearing in which its record became consequential.

The interrogation’s importance therefore lies not in a conclusive finding about espionage, but in the collision of political judgment, personal loyalty, and the machinery of security. Oppenheimer tried to distinguish public, authorized cooperation with the Soviet ally from covert access to scientific work; at the same time, he withheld names to protect people he considered innocent. Because his account was secretly captured, its ambiguities outlasted the conversation itself. What had begun as a warning about Eltenton became a permanent document through which Oppenheimer’s judgment and honesty would later be scrutinized.