Documents relating to 1941 Bohr-Heisenberg meeting

Document 11a. Page 4 of 5.

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Incomplete draft of letter from Bohr to Heisenberg, never sent.

First of three versions: draft in Aage Bohr's handwriting.

Undated Five numbered pages.

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I dit brev til Jungk kommer du også ind på Jensens besøg i København i 1943 under sine rejser til Norge for at medvirke ved bestræbelserne på at forøge produktionen af tungt vand. Det er rigtigt, at Jensen over for os understregede at dette arbejde kun tog sigte på energifrembringelse til industrielle formål, men selv om vi var tilbøjelige til at nære tillid til hans oprigtighed, følte vi os på ingen måde sikre på hvormeget han selv vidste om hele arbejdet i Tyskland. Der fremkom jo også i de år fra tysk side ofte bebudelser af nye afgørende våben. Ved møderne med Jensen var jeg ligeledes yderst tilbageholden som følge af den stadig voksende spionering fra det tyske politis side.

Da jeg, for at undgå en umiddelbart forestående arrestation, måtte flygte til Sverige i efteråret 1943 og derfra kom til England, lærte jeg for første gang om det da allerede vidt fremskredne amerikansk–engelske atomprojekt. Spørgsmålet om, hvor langt man var kommet i Tyskland, optog ikke alene fysikerne, men også regeringerne og efterretningstjenesten, og jeg blev inddraget i drøftelserne derom. Jeg fortalte om alle vore oplevelser i København, i hvilken forbindelse også spørgsmålet blev rejst hvad bemyndigelse der fra den tyske regerings side måtte være givet dig til at berøre et så farligt spørgsmål, med så store politisk konsekvenser over for nogen i et besat og fjendtligt indstillet land. Drøftelserne fik dog ikke nogen afgørende betydning, hverken i den ene eller anden retning, idet

In your letter to Jungk you also mention Jensen’s visits to Copenhagen in 1943 during his journeys to Norway to participate in the efforts to increase the production of heavy water. It is true that Jensen emphasized to us that this work was only aimed at the production of energy for industrial purposes, but although we were inclined to trust his sincerity, we felt in no way certain regarding how much he himself knew about the whole effort in Germany. In those years there were often announcements from Germany of new and decisive weapons. At the meetings with Jensen, I was likewise extremely cautious as a result of the constantly growing surveillance on the part of the German police.

When I had to escape to Sweden in the autumn of 1943 in order to avoid imminent arrest and from there went to England, I learned for the first time about the already then well-advanced American–English atomic project. The question of how far Germany had come occupied not only the physicists but also the governments and the intelligence service, and I became involved in the discussions about this. I recounted all our experiences in Copenhagen, and in this connection the question was also raised about what authorization might have been given to you by the German government to touch upon such a dangerous question, with such great political consequences, with someone in an occupied and hostile country. However, the discussions had no decisive influence one way or the other, since