How German nuclear scientists reacted to the news of Hiroshima

As part of Operation Epsilon, captured German nuclear physicists were secretly recorded at Farm Hall, a house in England where they were interned. Here’s how the German scientists reacted to the news (on August 6th, 1945) that an atomic bomb had been dropped on Hiroshima, taken from the now-declassified transcripts (pp. 116-122 of this copy):

Otto Hahn (co-discoverer of nuclear fission): I don’t believe it… They are 50 years further advanced than we.

Werner Heisenberg (leading figure of the German atomic bomb effort): I don’t believe a word of the whole thing. They must have spent the whole of their £500,000,000 in separating isotopes: and then it is possible.

In a margin note, the editor points out: “Heisenberg’s figure of £500 million is accurate. At the then-official exchange rate it is equal to $2 billion. President Truman’s account of the expense, released on August 6, stated: ‘We spent $2,000,000,000 on the greatest scientific gamble in history — and won.’ …Isotope separation accounted for a large share but by no means the whole of that…”

Hahn: I didn’t think it would be possible for another 20 years.

Karl Wirtz (head of reactor construction at a German physics institute): I’m glad we didn’t have it.

Carl Friedrich von Weizsäcker (theoretical physicist): I think it is dreadful of the Americans to have done it. I think it is madness on their part.

Heisenberg: One can’t say that. One could equally well say “That’s the quickest way of ending the war.”

Hahn: That’s what consoles me.

Heisenberg: I don’t believe a word about the bomb but I may be wrong…

Hahn: Once I wanted to suggest that all uranium should be sunk to the bottom of the ocean. I always thought that one could only make a bomb of such a size that a whole province would be blown up.

Weizsäcker: How many people were working on V1 and V2?

Kurt Diebner (physicist and organizer of the German Army’s fission project): Thousands worked on that.

Heisenberg: We wouldn’t have had the moral courage to recommend to the government in the spring of 1942 that they should employ 120,000 men just for building the thing up.

Weizsäcker: I believe the reason we didn’t do it was because all the physicists didn’t want to do it, on principle. If we had all wanted Germany to win the war we would have succeeded.

Hahn: I don’t believe that but I am thankful we didn’t succeed.

There is much more of interest in these transcripts. It is fascinating to eavesdrop on leading scientists’ unfiltered comments as they realize how badly their team was beaten to the finish line, and that the whole world has stepped from one era into another.


  1. Ummm says

    This should be taken in the context that the scientists likely knew they were being recorded and were trying to look favorable to the Americans.

    • Mike Ryan says

      Diebner: “I wonder whether there are microphones installed here?”
      Heisenberg: “Microphones installed? (laughing) Oh no, they’re not as cute as all that. I don’t think they know the real Gestapo methods; they’re a bit old fashioned in that respect.”

  2. Rick says

    How ironic and appropriate that Heisenberg says “I don’t believe a word about the bomb but I may be wrong….”

  3. Martin Page says

    Both Germany and Japan are portrayed as losers in the ‘race’ for the atomic bomb. It is not widely known that Heisenberg and Nishina were students together under Niels Bohr and nurtured in the rarefied world of quantum physics. An atomic bomb would therefore would appears as an anathema. Both used the excessive weight of the thing as an impediment to its realisation.
    In the Farm Hall transcripts, Heisenberg maintains that it would require 10 tons and later 1 ton of U 235. Only much later in his lecture does he finally quote 16 Kg. When Otto Hahn askes how does the bomb work, Heisenberg say ”if each neutron instantly begets two children” etc. This from a man who is developing a heterogeneous nuclear reactor, a mathematician who would be using Helmholtz and Laplace transforms in this work.
    In the Tonizo transcripts of 2nd July 1943, to quote Nishina ; “that is to say the tamper, the weight of this thing would be enormous and because of this, the opinion is that it is not suitable (as a(bomb)”.
    ” Sunawachi bombu no jyuro jindai naru mono to naru wo motte tekito narazaru beshi tono kenkai nari”.
    At a later meeting Nishina gives a description of the physics of the Godiva experiment that was undertaken in the Manhattan project and the concept of 2nd criticality.
    Both Heisenberg and Nishina are portrayed as either incompetent or mistaken but as a physicist I can see they knew more than they were prepared to say.

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