The following is an interview with Otto Hahn, the German scientist who discovered nuclear fission in 1938. Hahn talks about his work during World War I, under the direction of Haber, on the development of chemical weapons.

INTERVIEWER: Professor Hahn, how do you explain the fact that you, an organic chemist who had been working in the field of radiochemistry form more than a decade, were assigned to work on gas warfare?

PROFESSOR HAHN:First of all, Geheimrat Haber had seen chlorine as a possibility in gas warfare. There is chlorine in every chemical laboratory, and every chemist has worked with it at some time.

INTERVIEWER: You have told us that you had qualms about helping to organize gas warfare, and that you spoke to Geheimrat Haber about your scruples.

PROFESSOR HAHN:I knew that the Hague Convention prohibited the use of poison in war. I didn't know the details of the terms of the Convention, but I did know of that prohibition. Haber told me the French already had rifle bullets filled with gas, which indicated that we were not the only ones intending to wage war by that means. He also explained to me that using gas was the best way of bringing the war to end quickly.

INTERVIEWER: And you found those arguments convincing?

PROFESSOR HAHN:You might say that Haber put my mind at rest. I was still against the use of poison gas, but after Geheimrat Haber had put his case to me and explained what was at stake, I let myself be converted and I then threw myself into the work wholeheartedly. As you know, many other renowned scientists also put themselves at his disposal, among them Geheimraete Willstaetter and Wieland and my friends James Franck and Gustav Hertz.

INTERVIEWER: The first job, I understand, was to find a way of using chlorine in an offensive. Had you any information about such experiments being done on the enemy side?

PROFESSOR HAHN:We knew nothing about that. At first the English were very surprised by our disregarding the Hague Convention. But from 1916 onward they used at least as much poison as we did. During the war there was a rumor that Haber would be regarded as a war criminal and would be brought before an international court to be condemned to death. Towards the end of the war he became very nervous about this and disappeared for a time. When I saw him again he was wearing a beard, in order to avoid being recognized instantly. But then, after the war, no steps were taken against him.

INTERVIEWER: Nor against the other scientists, including yourself?

PROFESSOR HAHN:No. None.

INTERVIEWER: Do you think it possible that the enemy shared the general respect for Geheimrat Haber as an eminent scientist who had, after all, earned humanity's gratitude for a great work on behalf of civilization? I mean, it was he who, with his co­worker Geheimrat Bosch, succeeded in fixing atmospheric nitrogen in the form of ammonia to get the starting material for artificial fertilizer. He received the Nobel Prize for that.

PROFESSOR HAHN:Of course he was respected as a distinguished scientist.

INTERVIEWER: It has often been said that without Haber and Bosch and their nitrogen fixation Germany would not have been able to keep the war going for so long.

PROFESSOR HAHN:That may well be so. Artificial fertilizer was an absolute necessity to starving Germany. But the nitrogen fixation was just as important for agriculture in peacetime and it need hardly be said that it still is so today.

INTERVIEWER: Now, to come back to Haber's role as the initiator of gas warfare ­ after chlorine he introduced phosgene, didn't he?

PROFESSOR HAHN:A simple compound but a terrible poison. Up to that time, nobody had ever realized how extraordinary toxic phosgene is. It is more toxic than prussic acid. One single inhalation is lethal. We tested it out.

INTERVIEWER: One cannot help feeling some amazement that you and the elite of German chemists experimented on yourselves with such dangerous substances.

PROFESSOR HAHN:Why? We volunteered, we offered our services. Of course it did take a bit of nerve, but we were specialists, after all, so we were best qualified to estimate the risks. Actually it was only Franck and myself who carried out the tests to establish how long newly manufactured gas­masks would remain effective against high concentrations of phosgene.

INTERVIEWER: You mean James Franck, who was later awarded the Nobel Prize and who collaborated with the American nuclear scientists during the Second World War? But you also worked with other poison gases, Blaukreuz and Gruenkreuz. You have not made any mention of the third of those mustard­gases, Gelbkreuz.

PROFESSOR HAHN:No, I never worked on Gelbkreuz. It was the most unpleasant of all the poison gases. But I have no experience of it.

INTERVIEWER: You have told us that you several times saw with your own eyes the effect of poison gases on enemy soldiers. And you also say that what you saw left a very deep impression on you.

PROFESSOR HAHN:Yes, that is true. I felt profoundly ashamed, I was very much upset. First we attacked the Russian soldiers with our gases, and then when we saw the poor fellows lying there, dying slowly, we tried to make breathing easier for them by using our own life­saving devices on them. It made us realize the utter senselessness of war. First you do your utmost to finish off the stranger over there in the enemy trench, and then when you're face to face with him you can't bear the sight of what you've done and you try to help him. But we couldn't save those poor fellows.

Taken From: Otto Hahn: My Life. New York: Herder and Herder, 1968, p. 130­133.