Whenever the U.S. program bogged down in bureaucratic doubt Hitler and his war machine rescued it. That summer's massive escalation, code-named Operation Barbarossa, was the opening of the Eastern Front at dawn on the morning of Sunday, June 22, a surge eastward with 164 divisions, including Finnish and Rumanian components, toward
The effect on Conant of his London experiences and the widening war was paradoxically to increase his skepticism of the program he had just accepted assignment to administer:
What worried me about Compton's first report, I told Bush, was the assumption that achieving a chain reaction was so important that a large expenditure of both money and manpower was justified. To me, the defense of the free world was in such a dangerous state that only efforts which were likely to yield results within a matter of months or, at most, a year or two were worthy of serious consideration. In that summer of 1941, with recollections of what I had seen and heard in England fresh in my mind, I was impatient with the arguments of some of the physicists associated with the Uranium Committee whom I met from time to time. They talked in excited tones about the discovery of a new world in which power from a uranium reactor would revolutionize our industrialized society. These fancies left me cold. I suggested that until Nazi Germany was defeated all our energies should be concentrated on one immediate objective.
Having experienced the London Blitz, Conant had developed a siege mentality; Bush, as Conant points out, “was faced with a momentous decision as to priorities.” Both men wanted a hard, practical assessment. They decided Compton's report needed an injection of common sense in the form of engineering expertise. Compton discreetly retired from the line; W. D. Coolidge, the General Electric scientist, temporarily took his place. Conant added an engineer from Bell Laboratories and another from Westinghouse and early in July the enlarged committee reviewed the first review.
Briggs was a convincing witness. By then he had received the April 9 minutes of a MAUD technical subcommittee meeting where Peierls reported that cross-section measurements confirmed the feasibility of a fast- neutron bomb. Briggs had also just learned from Lawrence that plutonium had a cross section for fast fission some ten times that of U238. Lawrence even submitted a separate report on element 94 that emphasized for the first time in U.S. official deliberations the importance of fast fission over slow. But Briggs was still preoccupied with a slow-neutron chain reaction for power production and so was the second NAS report. “In the summer of 1941,” John Dunning's associate Eugene Booth remembers, “Briggs visited us in the basement of Pupin at Columbia to see our experiment for the separation of U235 by [gaseous] diffusion of uranium hexafluoride. He was interested, blessed us, but sent us no money.”
The American program was in danger for its life that summer, Compton thought: “The government's responsible representatives were… very close to dropping fission studies from the war program.” He believed the program was saved because of Lawrence's proposal to use plutonium to make a bomb. The fissibility of 94 may have convinced Compton. It was not decisive for the government's responsible representatives. They were hard men and needed hard facts. Those began to arrive. “More significant than the arguments of Compton and Lawrence,” writes Conant, “was the news that a group of physicists in England had concluded that the construction of a bomb made out of uranium 235 was entirely feasible.”
The British had been trying all winter and spring to pass the word. In July they tried again. G. P. Thomson had assembled a draft final report for the MAUD Committee to consider on June 23, the day after Barbarossa exploded across the Balkans and eastern Poland. Charles C. Lauritsen of Caltech, a respected senior physicist, was beginning work for the NDRC developing rockets and happened to be in London conferring with the British at the time of the MAUD draft. The committee invited him to attend its July 2 meeting at Burlington House. Lauritsen listened carefully, took notes and afterward talked individually with eight of the twenty-four physicists now attached to the work. When he returned to the United States the following week he immediately reported the MAUD findings to Bush. “In essence,” says Conant, “he summarized the ‘draft report.’” The physicists Lauritsen had interviewed had all pushed for a U.S.-built gaseous-diffusion plant.
The British government would not officially transmit the final MAUD Report to the United States government until early October, but the committee approved it on July 15 (and thereupon promptly disbanded) and by then Bush had been passed a copy of the Thomson draft, which embodied the essential findings. The MAUD Report differed from the two National Academy studies as a blueprint differs from an architect's sketch. It announced at the outset:
We have now reached the conclusion that it will be possible to make an effective uranium bomb which, containing some 25 lb of active material, would be equivalent as regards destructive effect to 1,800 tons of T.N.T. and would also release large quantities of radioactive substances… A plant to produce
Of conclusions and recommendations the report offered, crisply, three:
(i) The committee considers that the scheme for a uranium bomb is practicable and likely to lead to decisive results in the war.
(ii) It recommends that this work continue on the highest priority and on the increasing scale necessary to obtain the weapon in the shortest possible time.
(iii) That the present collaboration with America should be continued and extended especially in the region of experimental work.
“With the news from Great Britain unofficially in hand,” Conant concludes in a secret history of the project he drafted in 1943, “… it became clear to the Director of OSRD and the Chairman of NDRC that a major push along the lines outlined was in order.”
They still did not immediately organize that push. Nor was Conant, to his postwar recollection, yet convinced that a uranium bomb would work as described. British research and considered judgment had at least proposed a clear-cut program of
“If each necessary step requires ten months of deliberation,” Leo Szilard had complained to Alexander Sachs in 1940, “then obviously it will not be possible to carry out this development efficiently.” The American program was moving faster now than that, but not by much.
While Lawrence and Compton championed plutonium that summer, a big, rawboned, war-battered Austrian hiding out within the German physics establishment tried to keep the fissile new element out of sight. He was an old friend of Otto Frisch:
Fritz Houtermans and I had met in Berlin, but in London [before the war] I saw a lot more of that impressive eagle of a man, half Jewish as well as a Communist who had narrowly escaped the Gestapo. His father had been a Dutchman, but he was very proud of his mother's Jewish origin and liable to counter anti-semitic remarks by retorting “When your ancestors were still living in the trees mine were already forging cheques!” He was
