Plans to abduct or assassinate Heisenberg

Plans to abduct or assassinate Heisenberg arose from Allied fears about German nuclear research, but never became an operation against Werner Heisenberg. J. Robert Oppenheimer treated the proposed kidnapping as a matter for the authorities, not a plan to endorse; when Leslie Groves later sent an agent to Switzerland to stalk Heisenberg, the agent ultimately chose not to attempt an assassination.

The warning and Weisskopf’s proposal

In late October 1942, J. Robert Oppenheimer received a letter marked “secret” from his friend and colleague Victor Weisskopf. Weisskopf relayed alarming news from Wolfgang Pauli, then living in Princeton: Heisenberg had been appointed director of the Kaiser-Wilhelm Institute, a nuclear research facility in Berlin, and was scheduled to lecture in Switzerland. The news made the possibility of encountering Heisenberg outside Germany seem urgent to Weisskopf and Hans Bethe, with whom he had discussed what might be done.

Weisskopf proposed kidnapping Heisenberg in Switzerland and volunteered to carry it out. His rationale was starkly framed as wartime reciprocity: “That’s what the Germans would do if, say you or Bethe would appear in Switzerland.” The proposal converted a report about a physicist’s travel into a possible covert operation, reflecting how the prospect of German nuclear work could make extraordinary measures seem thinkable.

Oppenheimer’s guarded response

Oppenheimer replied promptly, thanking Weisskopf for his “interesting” letter. He said that he already knew of Heisenberg’s planned visit and had discussed the matter with the “proper authorities” in Washington. Those authorities were Vannevar Bush and Groves; Oppenheimer forwarded Weisskopf’s letter to them. His response acknowledged the proposal and conveyed that it was receiving official attention, but did not endorse a kidnapping.

His caution had a strategic basis: even a successful abduction could alert the Nazis to the importance the Allies attached to nuclear research. Yet Oppenheimer did not regard the Swiss visit as irrelevant. In writing to Bush, he remarked that Heisenberg’s proposed visit “would seem to afford us an unusual opportunity.” The juxtaposition captures the uncertainty in his position: the occasion might have intelligence value, while an overtly consequential operation could expose Allied priorities.

Groves’s later operation

The idea resurfaced later in the war in a more concrete form. In December 1944, Groves dispatched Moe Berg, an OSS agent and former baseball player, to Switzerland, where Berg stalked Heisenberg. This was a later initiative, distinct from Weisskopf’s 1942 proposal and Oppenheimer’s guarded referral of it. Berg ultimately decided not to attempt an assassination. The plan therefore ended not in Heisenberg’s capture or death, but in a decision not to carry out the attack.

Significance

The episode shows how the possibility of an enemy nuclear program could press Allied scientists and officials toward considering actions far outside ordinary scientific work. Its sequence matters: Weisskopf proposed a kidnapping and volunteered; Oppenheimer referred the proposal to Bush and Groves without endorsing it; Groves later sent Berg to Switzerland; and Berg abandoned the assassination attempt. The record supports a history of proposals and pursuit, not a completed operation against Heisenberg.