sider. At min tavshed og alvor, som du skriver i brevet, kunde opfattes som forskrækkelse over dine meddelelser om at man kunde lave atombomben, er en helt ejendommelig misforståelse, der må skyldes den store spænding i dit eget sind. Fra den dag tre år før, hvor jeg blev klar over at langsomme neutroner kun kunde frembringe fission i Uran235 og ikke 238 var det jo indlysende for mig at man ved at skille uranerne vilde have en bombe med sikker virkning. Jeg havde endda i Juni 1939 i Birmingham holdt et offentligt foredrag om uranspaltningen, hvor jeg talte om en sådan bombes virkninger, men naturligvis tilføjede at de tekniske forberedelser vilde være så store at man ikke vidste hvor hurtigt de kunde overkommes. Hvis noget i min opførsel kunde tyde på forskrækkelse lå det derfor ikke i sådanne meddelelser, men i efterretningen om at man, så vidt jeg måtte forstå, i Tyskland så energisk deltog i et kapløb om at komme først med atomvåben.

I øvrigt vidste jeg dengang intet om hvor langt man allerede var kommet i England og Amerika hvad jeg jo først fik at vide da det året efter lykkedes mig at komme til England efter meddelelse om at den tyske besættelsesmagt i Danmark havde truffet forberedelse til min arrestation.

Alt dette er jo kun en gengivelse af, hvad jeg klart husker fra vore samtaler og som i den næstfølgende tid naturligvis var genstand for indgående drøftelse på Instituttet og med andre fortrolige venner i Danmark. En ganske anden sag er at jeg dengang og siden altid har haft det bestemte indtryk at du og Weizsäcker

sides engaged in mortal combat. That my silence and gravity, as you write in the letter, could be taken as an expression of shock at your reports that it was possible to make an atomic bomb is a quite peculiar misunderstanding, which must be due to the great tension in your own mind. From the day three years earlier when I realized that slow neutrons could only cause fission in Uranium 235 and not 238, it was of course obvious to me that a bomb with certain effect could be produced by separating the uraniums. In June 1939 I had even given a public lecture in Birmingham about uranium fission, where I talked about the effects of such a bomb but of course added that the technical preparations would be so large that one did not know how soon they could be overcome. If anything in my behaviour could be interpreted as shock, it did not derive from such reports but rather from the news, as I had to understand it, that Germany was participating vigorously in a race to be the first with atomic weapons.

Besides, at the time I knew nothing about how far one had already come in England and America, which I learned only the following year when I was able to go to England after being informed that the German occupation force in Denmark had made preparations for my arrest.

All this is of course just a rendition of what I remember clearly from our conversations, which subsequently were naturally the subject of thorough discussions at the Institute and with other trusted friends in Denmark. It is quite another matter that, at that time and ever since, I have always had the definite impression that you and Weizsäcker