Both Wick and Amaldi had served in the Italian Army and since the surrender had been hiding in Rome. During the war they had engaged in theoretical research principally on isotope separation, neutron, infrared and cosmic rays. They had no direct information about German research in the field of nuclear fission, for they had never been asked to do any work with or for the Germans. They claimed not to understand the significance of heavy water, and they were not aware of any new activity at the Joachimsthal uranium mines in Czechoslovakia.
Wick had made a trip into Germany during June and July of 1942, and had seen and talked at some length with a number of German physicists at that time and, together with Amaldi, had been shown some of the correspondence between various German scientists; thus they were able to supply us with some useful information. They were most co-operative, and what they gave us was the basis for the compilation of brief accounts of the activities and locations of a number of Germans who were of outstanding interest to the MED. Although later investigations in Germany proved that some of the information obtained in Rome was not wholly accurate, in the main it was well worth the trouble we had gone to in collecting it.
[…]
Throughout the European campaign, as far as atomic efforts were concerned, Alsos members had the tremendous advantage of knowing where they were going and whom and what they were seeking. When they landed on the Continent, they had in hand the fruits of Calvert’s labors, in the form of a comprehensive list of intelligence “targets” — the names of key individuals, where they worked and where they lived; and the location of the laboratories, workshops and storage points, and other items of interest to us. At the head of the list was the famous French atomic scientist, Frederic Joliot-Curie (later High Commissioner of Atomic Energy for France), and his equally famous wife, Irene Curie, the daughter of Madame Curie, discoverer of radium.
[…]
On August 25, they reached Paris, at the Porte d’Orleans, ahead of the French troops, and waited there for about half an hour until General LeClerc arrived with his armored division. The General led the triumphal entry, at 8:55 that morning, but tucked into the column, directly behind the first tank was an American jeep containing the first representatives of the U.S. Army: Pash, Calvert and two other Alsos agents.
[…]
There, on the steps of the university, they found Joliot and some of his staff, all wearing FFI arm bands. That evening they celebrated the liberation with Joliot by drinking some champagne he had reserved for the occasion. The American soldier’s staff of life, the K ration, served as the hors d’oeuvres. In keeping with the scientific surroundings, the champagne was drunk from laboratory beakers.
In the course of their conversation with Joliot, the names of two of his former colleagues came up: Hans von Halban, born an Austrian in Leipzig and later naturalized as a French citizen, and Lew Kowarski. Both men had left France for England in June of 1940 and had been working in the British Tube Alloys Project in Canada. Joliot immediately surmised that there was some connection between them, Pash and Calvert, and the uranium problem.
They did not openly tell him at first what they wanted of him. However, after an hour’s conversation, Joliot willingly told them just what they wanted to hear: that it was his sincere belief that the Germans had made very little progress on uranium and they were not remotely close to making an atomic bomb. He said he had refused to perform any war work for the Nazis and had forbidden them to use his laboratories for such purposes. However, after the occupation commenced, he said he did allow two German scientists to move into his laboratory to continue academic work on nuclear physics. He added that he talked with them frequently and clandestinely checked their work at night after the laboratory was closed, thus keeping constant surveillance on their activity. How true this all was we never knew.
[…]
The College of France, which was Joliot’s laboratory, owned a cyclotron, and a number of German scientists of interest to the MED had spent varying lengths of time there operating it. Among them was Professor Erich Schumann, who headed the German Army Research conducted by the Ordnance Department and who, during the war, served as the personal adviser on scientific research to Field Marshal Wilhelm Keitel. Schumann was credited with initiating work on the German uranium project, although by the end of 1942 his responsibilities had been transferred to the Reich’s Research Council.
Another visitor to Joliot’s laboratory was Dr. Kurt Diebner, who in 1939 had served as Schumann’s right-hand man and who had continued nuclear research under the Reich’s Research Council. Then there was Professor Walther Bothe, an outstanding German nuclear experimentalist in the physics laboratory of the Kaiser Wilhelm Institute for Medical Research. Dr. Abraham Essau, who until early 1944 was in charge of physics under the German Ministry of Education in the Reich’s Research Council, had made a number of visits to Paris. Essau had been president of the Ministry’s Bureau of Standards until January, 1944, when he was replaced as Plenipotentiary for Nuclear Physics by Walther Gerlach. There was also Dr. Wolfgang Gertner, an able German scientist who, before the war, had been associated with Ernest Lawrence in the United States. Gertner was an outstanding German authority on cyclotron operations. Joliot’s other visitors had included Dr. Erich Bagge, a member of the Kaiser Wilhelm Institute, who specialized in isotope separation, and Dr. Werner Maurer, an experimental physicist engaged in nuclear research.
Joliot consistently maintained that he had acquiesced in the Germans’ use of the cyclotron with the distinct understanding that its use would not be of direct military assistance to their war effort. There was no independent evidence that this condition was made. There may have been a promise made to him by some of the German scientists, or they may have said that there appeared to be no military possibilities that could result from the use of the cyclotron, but I never found any real proof of Joliot’s contention. Certainly, his subsequent behavior — and I shall come to that shortly — gave us room for doubt.
[…]
The most difficult problem that Calvert’s intelligence group had to tackle was to find out where Hitler was hiding his atomic scientists. They knew, as everyone did, that before the war the Kaiser Wilhelm Institute in Berlin had been a focal point for all atomic physicists and atomic research, not only in Germany, but in all of Europe. It was there that Otto Hahn and Fritz Strassman had carried out their startling experiments. It was also the home of Max Planck, the internationally famous atomic scientist.
As the war drew on, however, and the bombing of Berlin was stepped up, we had learned from both aerial reconnaissance and a Berlin scientist, who got word to us through the Norwegian underground, that research on uranium had been moved, presumably to a safer location, but where he did not know.
[…]
The first information had trickled through in the summer of 1943. It seemed so innocuous that we did not appreciate its full import until much later. It was in the form of a report from an ungraded1 Swiss informant, received by the British Secret Intelligence, stating that a certain Swiss scientist, who was allegedly pro-Nazi, was aiding in the development of an explosive a thousand times more powerful than TNT. His experiments and research were being conducted in the greatest of secrecy in an unused spinning mill in Bisingen, Germany. Inasmuch as Allied Intelligence was receiving hundreds of reports of this nature daily, and coupled with the absence from this one of any telltale words or phrases, such as uranium, atoms, heavy water, cyclotrons or the like, Calvert catalogued this item but did not attach immediate importance to it.
Next, in the fall of 1943, American censorship had intercepted a letter from a prisoner of war in which he mentioned that he was working in a “research laboratory numbered ‘D.’” The letter was postmarked Hechingen, Germany, which is three miles north of Bisingen, in the Black Forest region of Germany, where many secret German projects had been moved. But again the report was so scanty that one could hardly assume that Germany’s atomic research was being carried on in these outwardly sleepy little villages.
It.was not until the spring of 1944 that Calvert received his first solid information. Then the OSS reported from Berne, Switzerland, that a Swiss scientist and professor had said that Dr. Werner Heisenberg, an internationally famous nuclear physicist and one of Germany’s top atomic scientists—if not the top—was living near Hechingen. We knew from other intelligence that Heisenberg was working on the uranium problem. With this new bit of information, Calvert knew that he had found the hiding place of Hitler’s top atomic scientists.
[…]
Calvert’s next big problem was to try to penetrate the area. To do that he would have to get somebody who knew it extremely well. British Intelligence located a vicar living in England who before the war had been Vicar of Bisingen. He was able to pinpoint and identify buildings and factories for us. He also pointed out buildings that had housed spinning mills.
At the same time Calvert sent a very reliable and able OSS agent, Moe Berg, the former catcher of the Washington Senators and Boston Red Sox, and a master of seven foreign languages, into Switzerland to prepare for a surreptitious entry into the Hechin-gen-Bisingen area. While Berg was in Switzerland, he picked up additional information and, passing himself off as a Swiss student, even attended a lecture given by Heisenberg, who had been granted permission to travel outside Germany to deliver this one speech. When I heard of Calvert’s plan for Berg to go into the Hechingen-Bisingen area, I immediately stopped it, realizing that if he were captured, the Nazis might be able to extract far more information about our project than we could ever hope to obtain if he were successful.
[…]
Starting in July, Calvert put the Bisingen-Hechingen area under constant air-photo surveillance. The pilots who flew these missions were never told of the nature of the suspected targets, lest they be interrogated in the event of a crash landing. At first our aerial reconnaissance produced nothing new. Then in the fall of 1944, we had our biggest scare to date. After one aerial sortie it was observed that near the town of Bisingen a number of slave labor camps had been erected with incredible speed. Ground had been broken and a complex of industrial sites had mushroomed within a period of two weeks. Railroad spurs had been constructed; mountains of materials had been moved in; power lines had been erected; and there was every indication that something was being built that commanded the utmost priority. Aerial interpreters, intelligence officers, our own technicians and scientists were all baffled after studying the photographs. Nobody could offer any sensible explanation of this new construction. All we knew was that throughout the past year we had been getting reports that this area was housing Germany’s top atomic scientists. The only thing upon which we could all agree was that whatever the construction was, it was unique. Naturally the first question that came to our minds was whether this was the start of Germany’s “Oak Ridge.” If it was, we did not want to bomb it immediately, since that would only drive the project underground and we would run the risk of not finding it again in time. Yet we could not let construction progress too far, particularly since this was just at the time when it was thought that the Germans might withdraw to the Black Forest and make it a redoubt area. Fortunately our anxiety was short-lived, and the fear of a German atomic plant was dissipated almost as quickly as it had arisen, when some British mining experts recognized that what we had been observing so closely was nothing more than a new form of shale-oil-cracking plant.
[…]
Before the war, when Union Miniere was the world’s leading supplier of uranium and radium, a number of German firms had purchased uranium products for normal peacetime uses, as well as for retrading purposes. The shipments involved in such transactions normally consisted of less than a ton per month of assorted refined materials, but since June, 1940, orders from a number of German companies had increased spectacularly.
A preliminary study conducted by Union Miniere indicated that a quantity of material was still in Belgium. Part of it was ready for shipment, but probably had not yet been removed. When I learned of this, I immediately sent Furman back to Europe with instructions to locate and secure the material. He and Pash conferred with General Bedell Smith, who arranged for the British 21st Army Group to support Alsos in its recovery operations, without revealing to the British the name or purpose of the material being sought. The area where they expected the ore to be was then in the front lines of the British sector and under light sniper fire. Pash and two of his agents hunted for it from September 19 to 25 before they finally found it. The captured ores amounted to sixty-eight tons, which were placed under joint American and British control and removed from Belgium to the United States by way of England.
Information obtained in Belgium led to further investigations in Eindhoven, near Antwerp, where we learned that in May of 1940, nine cars containing approximately seventy-two tons of uranium ores had been shipped out to Le Havre, France, ahead of the German invasion. Apparently, the Germans had seized two of the nine carloads at Le Havre, while the remainder were rerouted to Bordeaux. I instructed Alsos to obtain clearance from Supreme Headquarters, and then to locate this material and secure as much of it as possible. Pash and Calvert concentrated at first on an area in the vicinity of Perigueux, France, and finally in early October expanded their search to include much of southwestern and southern France. They were greatly hindered in their search by the presence of several thousand German troops, who had been cut off south of the Loire River by the Seventh Army. Eventually, they found thirty tons of the missing ore in Toulouse, but the remaining forty-two tons eluded us.
Calvert had by then determined where almost all of the Union Miniere ore in Germany was located and asked permission to make plans to go behind the German lines to get it. I denied his request, for I thought that any such attempt would be doomed to failure, and, what was more important, it would alert the Germans to the fact that we considered the ore to be of such value that we would take great risks to obtain it.
[…]
This operation at Strasbourg was by far the most successful that Alsos had conducted up to that time. The information gained there indicated quite definitely that Hitler had been apprised in 1942 of the possibilities of a nuclear weapon. Nevertheless, all evidence from Strasbourg clearly pointed to the fact that, as of the latter part of 1944, the enemy’s efforts to develop a bomb were still in the experimental stages, and greatly increased our belief that there was little probability of any sudden nuclear surprise from Germany.
