My Dear Li: Correspondence, 1937–1946 by Werner and Elisabeth Heisenberg, edited by Anna Maria Hirsch-Heisenberg and translated from the German by Irene Heisenberg. Yale University Press, 312 pp., $40.00

Almost as soon as World War II ended in Europe, and with redoubled intensity after the bombing of Hiroshima, physicists all over the world began to ask how close the Germans had come to making an atomic bomb. But it was not clear whom to ask. Everything to do with development of the bomb was cloaked in secrecy and ten of the leading scientists involved in German atomic research had gone missing. One of them, Otto Hahn, the first to explain the fission process that made bombs possible, was on November 15, 1945, awarded the Nobel Prize in chemistry for his discovery, but the prize committee, it turned out, had no idea where Hahn was.

Among the few who did know were leading scientists who had developed the American bomb at Los Alamos in New Mexico. Many of them were Jews by Nazi standards who had fled Hitler’s Germany, including the physicists Hans Bethe and Victor Weisskopf, who had feared at the beginning of the war that the great German theoretical physicist Werner Heisenberg would build a bomb for Hitler. In 1942, learning that Heisenberg was going to give a scientific talk in Zurich, Bethe and Weisskopf had proposed an American operation to kidnap Heisenberg in Switzerland and even offered to take part themselves. This episode, improbable as it sounds, has been well documented elsewhere1 and after many twists and turns the original proposal led to Heisenberg’s detention in southern Germany in May 1945.

By November, Heisenberg, Hahn, and the other German scientists were being secretly held and closely monitored at a British country house called Farm Hall. The man who had the most to do with putting them there was the Dutch-born physicist Samuel Goudsmit, scientific director of an intelligence group called the Alsos mission. Goudsmit’s task was to track down the Germans who had been working on nuclear fission during the war and to answer the basic question—how close did the Germans get?

For the first year or two after the war pretty much everything Bethe and Weisskopf knew about the answer to the basic question came from information supplied by Goudsmit, a colleague in the Manhattan Project. The answer was not close at all. The Alsos mission found nothing that ever posed a threat to the Allies—instead there was a scattered program of small-scale, poorly funded research efforts that centered on an experimental reactor hidden in a cave in southern Germany that Heisenberg mistakenly hoped would soon be successful. When he first talked to Heisenberg in May 1945, Goudsmit had been privately scornful of German efforts that had achieved so little, and he dismissed Heisenberg’s attempts to explain the history of that little as the excuse-making of a scientist guilty of crude errors about the…