I have always considered Goudsmit’s opinion much to the point: “On the whole, we gained the definite impression that German scientists did not support their country in the war effort. The principal thing was to obtain money from the government for their own researches, pretending that they might be of value to the war effort. One genuine selling point which they used extensively was that pure research in Germany in many fields was far behind the United States.”
Although most of our objectives in Germany lay in the French zone of advance, one that was particularly important to us — the Auer-gesellschaft Works in Oranienburg, about fifteen miles north of Berlin — lay in what was to be the Russian zone. The information that Alsos had uncovered in Strasbourg had confirmed our earlier suspicions that the plant was engaged in the manufacture of thorium and uranium metals which were to be used in the production of atomic energy and hence probably for the manufacture of an atomic bomb. Since there was not even the remotest possibility that Alsos could seize the works I recommended to General Marshall that the plant be destroyed by air attack.
When he approved, I sent Major F. J. Smith, of my office, to explain the mission to General Carl Spaatz, who was then in command of our Strategic Air Forces in Europe. Spaatz co-operated wholeheartedly and, in a period of about thirty minutes during the afternoon of March 15, 612 Flying Fortresses of the Eighth Air Force dropped 1,506 tons of high explosives and 178 tons of incendiary bombs on the target. Poststrike analysis indicated that all parts of the plant that were aboveground had been completely destroyed. Our purpose in attacking Oranienburg was screened from Russians and Germans alike by a simultaneous and equally heavy attack upon the small town of Zossen, where the German Army’s headquarters were situated. I have since learned that as an entirely unexpected bonus the Zossen raid incapacitated General Guderian, then Chief of the German General Staff.
[…]
[T]he experimental uranium pile at Berlin Dahlem had been removed to Haigerloch, another small town near Hechingen. They reported a shortage of heavy water, explaining that their only source of it had been in Norway. The pieces of the puzzle were beginning to fall into place at last.
Bothe disclosed that the total German effort on atomic physics had consisted of himself and three helpers: Heisenberg with ten men; Dopel in Leipzig, assisted by his wife; Kirchner in Garmisch with possibly two assistants; and Stetter in Vienna with four or five others. Hahn, he said, was engaged in work on chemical problems.
The Heidelberg group told us that Gerlach’s approval was required before any physicist could obtain the means for scientific work. If he wanted the highest priority rating, called DE, he had to have the additional approval of Albert Speer, Minister of Armaments and Munitions.
Later, Bothe expressed his belief that the separation of uranium isotopes by thermal diffusion was impossible and indicated that the only work on isotope separation being done in Germany involved the centrifugal method. He added that this work was under the direction of Dr. Harteck. Bothe said he knew of no element higher than 93, although he recognized that since element 93 was a beta emitter, 94 must exist. He repeatedly expressed his opinion that the uranium pile as a source of energy was decades away and that the use of uranium as an explosive was altogether impracticable. He claimed not to know of any theoretical or experimental work being done in Germany on the military applications of atomic fission, but he agreed that such work could be under way without his knowledge.
After repeated questioning about the military value of the cyclotron, Bothe admitted that it had been regarded as a means for obtaining radioactive material for bombs.
[…]
Some of his personal letters, however, did cast doubts upon his assertion that he knew nothing of the work being done at Bisingen and Sigmaringen. From other sources, the interrogators learned that Bothe had returned a considerable quantity of uranium to Degussa after he had no further use for it.
Kuhn was present throughout Bothe’s interrogation. When it was over, he called one of the Alsos men aside and told him about the technical and scientific library of the German Chemical Society, of which he was the custodian. He claimed that it was the best of its kind in the world and included accounts of most of the German chemical activities in the war. To avoid the risks of heavy bombing, the library had been concealed in a number of caves and eventually was moved to a salt mine. Quite evidently, Kuhn preferred to have it taken over by the Americans rather than by the Russians. Unfortunately, it was behind the Russian lines.
[…]
Gertner said that he had worked with Joliot in Paris, from September of 1940 to July of 1943. He and Joliot, who had been close friends, had discussed the possibility of an atomic bomb and they had agreed that its development was not feasible.
[…]
He had reached the conclusion that it would be impossible to develop an atomic bomb because of the difficulties involved in separating isotopes. He further believed that, of all the separation methods, the centrifuge process offered the best prospects of success, but the low production rates that had been achieved by that method appeared to rule it out.
[…]
At about this time a major problem arose in Washington. The division of Germany into three zones of occupation had been arranged at Yalta. Later, when it was decided to establish a fourth zone to be occupied by the French, the readjustment of the American zone’s boundaries was handled by a committee of representatives of the State Department and of the Joint Chiefs of Staff. All the information that had been developed by Alsos indicated that the principal German work on atomic energy was being conducted in the general area Freiburg-Stuttgart-Ulm-Friedrichshafen, a large part of which would be turned over to the French. Hechingen lay near the center of this area and was in the French Army’s zone of advance, far removed from the zone of any American unit.
As I saw it, there could be no question but that American troops must be the first to arrive at this vital installation, for it was of the utmost importance to the United States that we control the entire area that contained the German atomic energy activities.
[…]
Consequently, I was forced to initiate some drastic measures to accomplish our purpose. One of these became known as Operation Harborage.
According to this plan, American troops would have to get into and hold the area long enough for us to capture the people we wanted, question them, seize and remove their records, and obliterate all remaining facilities, for my recent experiences with Joliot had convinced me that nothing that might be of interest to the Russians should ever be allowed to fall into French hands. Having reached this conclusion, I discussed the matter with Secretary Stimson and General Marshall together. After I had outlined briefly what I wanted, and we had considered the possible value of the information we might gather, we all turned to the big wall map in the Secretary’s office. To my great embarrassment, I was unable to find Hechingen on this map, and both the Secretary and the Chief of Staff were equally unsuccessful. Finally, Mr. Stimson summoned his aide, Colonel William H. Kyle, who succeeded eventually in locating our target at the bottom of the map, not more than two feet above the floor. If a photographer had been present at that time when the four of us were almost on our hands and knees, gazing intently at this point barely off the floor, he might well have caught one of World War II’s more interesting photographs.
A short discussion followed, during which General Marshall asked me how I would ensure the capture of our objectives. I suggested that the necessary American troops, possibly as much as a reinforced corps, should cut diagonally across the advancing French front. Marshall agreed and sent for Major General J. E. Hull, Head of the Operations Division, War Department, General Staff, telling him to issue instructions to General Eisenhower that would take care of our requirements.
[…]
Since the war, I have had occasion to discuss Operation Harborage and other Alsos operations with a number of the officers who were involved. In the course of these discussions, I have made it a point to tell them how much I always appreciated the co-operation given my representatives throughout the European Theater, when the only justification that they had for their apparently outlandish requests were simple memoranda addressed “To Whom It May Concern,” signed by either Secretary Stimson, General Marshall, or in a few cases by Colonel Frank McCarthy, the Secretary of the General Staff, and stating that their mission was of the utmost importance and that the Secretary of War would appreciate any assistance that could be rendered. Invariably, I have been told that it was not a case of kindness on the part of anyone in the European Theater, for these letters were most unusual and they realized that the matters involved must be of paramount importance. But over and above this, I have always felt great pride and pleasure upon hearing from these same commanders that while my officers were far from high-ranking, they were obviously of such ability and so convinced of the importance of their mission and the strength of their backing that they would have accomplished their missions no matter what obstacles stood in their way.
[…]
The WIFO plant was seized quickly and without incident. It was in a terrible condition from repeated bombings, but fortunately the manager had stayed on the job. Hidden in his house was an inventory of the plant’s property, which showed the whereabouts of the missing ore. Approximately eleven hundred tons of it were soon found stored in barrels under open sheds above-ground.
Most of the barrels were either broken or rotten, and it was obvious that the ore would have to be repacked before it could be moved. Complicating the problem was the fact that there were still many German units in the area. Fortune smiled upon Lansdale’s group again when the CIC agents found a barrel factory close at hand. The owner of the plant, who was also the local burgomaster, was soon prevailed upon to round up a sufficient number of laborers and to resume operations. During the next two weeks, with Agent Schriver in charge, and while under intermittent enemy fire, this factory turned out about twenty thousand fruit barrels.
Lansdale, in the meantime, had gone back to SHAEF, where he saw General Smith, and procured the services of a truck company. Trucks were in great demand at this period and the men, all Negroes with one white lieutenant, were exhausted from lack of sleep. They were further handicapped by being far from their normal maintenance bases. Nevertheless, they performed splendidly, and with the use of forced labor to repack and load the ore, the entire tonnage was removed during three days and nights to an airport hangar at Hildes-heim, near Hanover, well behind the Allied lines. A small amount of the ore was lost en route because of the number of truck ditchings caused by the extremely rough roads.
[…]
Observing the ore’s hue and noting that it was escorted by Hambro, a member of a well-known London banking family, many of the British were convinced that it was gold.
From Hanover, a considerable tonnage was moved by air to England. There was too much, however, to carry all of it in this manner, so arrangements were made to move the remainder by rail to Antwerp about two hundred miles away, and thence by ship to England. The precautions for insuring its delivery proved inadequate and somewhere along the line, probably in a switching yard, three cars disappeared, but after an intensive search, Agent Schriver found them, much to our relief.
From England, the ore was sent over to the United States.
[…]
It was becoming apparent that there were two groups in Germany working on the uranium pile, the first under Diebner at Frankfurt and the second under Heisenberg. Heisenberg’s group had been started in 1939 as a co-operative project of the most important physicists in Germany, with headquarters at the Institute of Physics in Berlin. There had been a certain amount of competition between the two groups, and quarrels over who would get materials continued even after all research had been officially consolidated under Gerlach. In Gertner’s opinion, the work done under Diebner was not so good as that over which Heisenberg had supervision.
Having pretty well exhausted its Heidelberg sources, Alsos next turned its attention to the Frankfurt area, where the uranium metal required by the German project had been produced. It found there that the degrees of purity achieved were not particularly high.
Following closely behind the advancing American front, on April 12, Alsos moved in and seized Diebner’s laboratory and offices, which were located in an old schoolhouse. Pash’s people found, however, that the majority of the scientists, together with most of their documents, materials and equipment, had been evacuated on April 8, to carry on their work elsewhere. Nevertheless they picked up some uranium oxide, various pieces of equipment, an extensive physics laboratory and many files. From these last it appeared that Germany’s military interest had been aroused in early 1940 by the experiments of Hahn and Strassman. It had been suggested then that uranium could be used to form an explosive, as well as to serve as a source of energy. Work to this end had been started by Heisen-berg’s group in Berlin, using uranium ore from Joachimsthal, which had been transformed into powdered U-238. This attempt at making a pile, however, was unsuccessful, primarily, I believe, because of the clumsiness of the experimental equipment. Heisenberg’s group continued experiments with their apparatus until about the end of 1941, always with negative results. In spite of their failures, Heisen-berg and von Weizsäxcker calculated that by making a number of modifications to their equipment a self-sustaining pile could be built. The work was transferred to Leipzig, where, in 1942, a pile gave positive results, but was not self-sustaining. This led to the initiation late in 1942 of the so-called large-scale experiments at Berlin Dahlem. Finally, late in 1944, an exponential pile was constructed in Berlin. This, however, was what might be termed purely academic scientific experimentation.
[…]
Something had to be done, and, as usual, Pash did it. He asked for help, and General Harrison gave him operational control of the 1279th Engineer Combat Battalion. With this force he seized Haiger-loch on April 23 and immediately began dismantling the laboratory. Its major feature was the exponential pile, which had been brought there from Berlin in February and concealed in a tunnel under a high cliff. The Alsos detachment was greatly assisted by the arrival of a number of British scientists under the leadership of Sir Charles Hambro, and was able to complete its operations in Haigerloch before the French reached there.
In the meantime, Pash, with one company of the 1279th Engineers, moved on to Hechingen, which he captured on April 24. Efforts to take this town the night before had been strongly resisted, but the final attempt was virtually unopposed. Pash seized a large atomic physics laboratory and a number of the leading German physicists, including von Weizsäxcker and Wirtz.
The next morning he moved into Tailfingen, where they took over a large chemistry laboratory and captured Otto Hahn and Max von Laue. At Stadtilm, Alsos had found signed receipts for all the secret reports and documents that had been sent to the various scientists. But as the men were picked up, one by one, they all announced blandly that everything had been destroyed. Hahn, however, answered promptly, “I have them right here.”
The capture of Hahn was simple. A German on the street, when questioned, pointed the way to an old school building which contained his laboratory. After the school was surrounded by troops, F. A. C. Wardenburg and James Lane, both chemical engineers from du Pont and two of our Alsos scientific personnel, walked in and asked for Hahn. They were shown into his laboratory and started their interrogations. “It was just like a business call on a customer,” was their apt description. By now French Moroccan troops were in the area, yet the mission still had not found the German stores of heavy water and uranium oxide that had been used in the Haigerloch pile. Fortunately, the French were few in number, and the many German units scattered throughout the countryside kept them fully occupied while Alsos was getting its job done.
Skillful questioning of the German scientists by Goudsmit and his associates finally disclosed the hiding place of the heavy water and uranium and, on April 26, the heavy water was removed from the cellar of an old mill near Haigerloch and sent back to Paris. About one and a half tons of small metallic uranium cubes were dug up from a plowed field just outside the town. These, too, were quickly dispatched to Paris. Both water and uranium were then shipped to the U.S., to be disposed of by the Combined Development Trust.
On the twenty-seventh, the German scientists were taken to Heidelberg for further questioning, and later removed to Rheims. As they were in the act of leaving, von Weizsäxcker suddenly blurted out the information necessary to locate the still missing records of the German research programs. They were sealed in a metal drum, which had been deposited in the cesspool in back of von Weizsäxcker’s house.
By the end of April, Alsos was heavily engaged in mopping-up activities. Most of the material we wanted had been secured. A few important scientists — notably Heisenberg — still eluded us. But, generally, our principal concern at this point was to keep information and atomic scientists from falling into the hands of the Russians.
The Alamogordo test, General Groves explains (in Now It Can Be Told: The Story of the Manhattan Project), had not set aside all doubts about the bomb: