MUCH of "Heisenberg's War" recounts a series of very strange, faint signals sent to the Allies from the German scientific community, especially from Heisenberg's inner circle. Prominent among them were leaks about the status of researcha nd development on nuclear energy in Germany. "There is not even one case of similar indiscretion among the Allied scientists who built the American bomb," Mr. Powers observes. He also makes much of a handful of explicit messages reporting intentional slowdowns. In March 1941, for example, a physicist close to Heisenberg, Fritz Houtermans, instructed a friend leaving for the West to tell American scientists that "Heinsenberg himself tries to delay...as much as possible" work on German bomb. Houtermans echoed this message in his first personal encounter with Allied scientists at the war's end, when he was debriefed in April 1945 by Goudsmit.

When Goudsmit reached Heinsenberg's office in Germanyu at the end of the war, he found on Heisenberg's desk a picture of the two of them together at the university of Michigan in 1939. But when Goudsmit encountered Heisenberg himself he refrained from asking his longtime acquaintance for an accounting of his wartime activities, the subject of endless speculation in Goudsmit's circles throughout the war. At that moment Goudsmit had many things on his mind. He had recently learned - from Otto Hahn, as it happened - of the death of his parents at Auschwitz.

It was Goudsmit who finally selected Heisenberg, Hahn and eight other German scientists for captivity. And once they were interned at Farm Hall, where Allied electronic ears could eavesdrop on them, they gave unwitting testimony that is relevant to Mr. Powers's argument. Heisenberg's young protege Carl Friedrich von Weizsacker (the son of Baron Ernst von Weiszsacker, the second in command at Hitler's foreign office, and the brother of the current President of Germany, Richard von Weizsacker) proclaimed that the Germans hadn't won the race to the atomic bomb because they had not really wanted to. Heisenberg spoke to the same effect, and Hahn expressed gratitude that they had failed.

The confused speculations about technical issues prove that most of the German scientists, includign Walter Gerlach, the project director, were far from understnading how an atomic bomb would work. But Heisenberg was exceedingly quick to figure it out on the basis of fragmentary news reports about the Hiroshima bomb, and he explained it to the others in remarkably accurate terms. "What the Farm Hall transcripts show unmistakably," Mr. Powers asserts, "Is that Heisenberg did not explain basic bomb physics to the man in charge of the German bomb program until the war was over."

But the Farm Hall transcripts create more problems for Mr. Powers than he fully acknowledges. Heisenberg was manifestly shocked by the news of the American bomb, and was at first adamant that it could not possibly be a uranium-based weapon. Had he been withholding the anaylsis he set forth int he days that followed, and had he believed that a significant difference might have been made by ideas he had kept to himself, he surely would not have been so flummoxed to hear that the deed was actually possible.

Moreover, the transcripts show the Germans to have seen themselves in a real race, and to have lost it. Even Hahn, whose professions of discomfort at the thought of Hilter with an atomic bomb are the most credible, immediately addressed Heisenberg as the leader of a beaten team: "At any rate, Heisenberg, you're just second-raters and you may as well pack up." Further, Hahn rejected outright Mr. von Weizsacker's claim that they lost because they hadn't really tried to win; and others, out of earshot of Mr. von Weizsacker, declared that he certainly did not speak for them.

I believe Mr. Powers exagerates the depth and consistency of Heisenberg's reluctance to see Nazi Germany equipped with an atomic bomb. The evidence he presents can support, instead, the thesis that from Farm Hall onward Heisenberg and Mr. von Weizsacker inflated what had been a mild and episodic ambivalence into a principled stand calculated to enhance their position in Germany's postwar scientific establishment and in the international scientific community.