“We Knew That If We Succeeded, We Could At One Blow Destroy A City”


What are your thoughts about Dr. Heisenberg’s involvement in the German nuclear effort and in Germany’s failure to produce a viable weapon?

Heisenberg worked on it as a German citizen, but he was not a Nazi. He was almost sent to a concentration camp. He had to work on it because he couldn’t leave his country. His attitude normally would have been: “This thing, let’s get it done.” In this case his attitude was different, thank God. He wanted to do it, yes, but not in his heart. He had an obligation to do it, but I believe he did not succeed because he was not really convinced that he must succeed. During the war of course I did not know that, though I knew always that Heisenberg was a very decent person.

For the Germans, the British, or the Americans, the engineering problems in 1939 must have seemed overwhelming.

We did not know how difficult it would be. That there would be people in Germany who would want to use it to help Hitler rule the world, I have no doubt. All Heisenberg wanted was for the war to be over and for his country, Germany, not to suffer very badly.

Did you know intuitively that if a way could be found to purify enough U-235, a crude but deliverable weapon was a certainty?

I am tempted to say yes. We knew that if we succeeded, we could at one blow destroy a city.

Germany surrendered shortly before your final push toward the Trinity test. What effect, if any, did the loss of the original threat have on the pace of work at the lab?

The matter was hardly discussed. We were close to the end, and there was no doubt in people’s minds about demonstrating the explosion, which happened in the middle of July. I remember driving away from that knowing that next time it would not be a demonstration, and I felt very worried. So did many other people in Los Alamos. After the Japanese missions we received the news that the war was over, and most doubts ended. There was a feeling of joy and celebration at the lab. We had made a big contribution to ending the war. Some celebration was justified, but I did not wholeheartedly participate.

May I ask you to recall the morning of the Trinity test, July 16?

That is a very sharp memory. I was with a group of people, I don’t know how far, maybe 20 miles from the point of explosion. We were told to lie down with our backs to the explosion. I obeyed and did lie down, but I did not turn my back to the explosion. I looked straight at it. We were given weld- ing glasses to put before our eyes to shield them from possible radiation. At our distant observing station we had reports from time to time, but then before the shot the reports stopped and we did not know what had happened. Maybe the shot was called off. Then came the time, the actual time. I was, as I told you, looking straight at the object. It was early in the morning, the sun wasn’t up yet. There was a little light—and the first seconds, a disappointment. Is that all? So I tipped the welding glasses and looked down at the sand next to me, and that gave an effect as when it’s midday and a heavy curtain moves on your window and the sunlight is streaming in. And that was only reflected light. Then I was impressed. I took off the glasses and looked at it, and there was a fireball rising, illuminating the whole world. Then after maybe 10 minutes, 15 minutes, we got up and started to walk away. Things were different. There was a strong feeling that whatever came next, it would be much more than a fireball.

Your primary working relationship at Los Alamos was with Robert Oppenheimer, who recruited most of the scientists for the lab. What are your memories of him?

Plenty, and not easy to tell. I want people to hear the story. To many of the people Oppenheimer was a motivator. He understood what people said, he understood what made them tick, and he encouraged them. He was, once he undertook the job, very anxious that he should succeed. He would say of Japan that it’s a terrible thing, they have no weapons, the war is over, but let’s do it. Oppenheimer was not a person without contradictions.


“I took off the glasses and looked at it, and there was a fireball rising, illuminating the whole world.“

With all the dossiers compiled on Oppenheimer and his family and friends, the FBI actually managed to miss the two Soviet spies who really were working at the lab. Were you surprised by the Soviet detonation in 1949 or the revelations of how close their agents actually got to your work? I’m thinking, of course, of Klaus Fuchs.

They had a very effective spy in Klaus Fuchs. He was a German and a very nice person, a highly intelligent person. I don’t know what the Nazis did to his family, but they did terrible things. He was actually informing the Soviets about the essential things we did. He got money for it, but I’m absolutely certain that he did not do it for money. I could not disagree with his actions more than I do, yet he behaved as a friend, and somehow I cannot think about it in very different terms.