What People Don't Know About the World War II Race for Nuclear Weapons
What People Don’t Know About the World War II Race for Nuclear Weapons

What People Don’t Know About the World War II Race for Nuclear Weapons

Larry Holzwarth - May 31, 2021

What People Don’t Know About the World War II Race for Nuclear Weapons
After Oranienburg was assigned to the Soviet zone of occupation, Groves requested the research facilities there be bombed by the Army Air Force. US Army

13. The Alsos mission moved into Germany in early 1945

By March, 1945, Alsos teams returned to Strasbourg, and opened another facility in Aachen. From there analysis of captured documents revealed extensive atomic research in several locations, some still out of reach of the Allied Armies. When Alsos missions identified an industrial facility at Oranienburg as a thorium and uranium processing site, General Groves prevailed on the 8th Air Force to bomb the facility. Plans called for the Soviets to occupy the site post-war. The still persistent rumors of the German’s possessing atomic weapons ensured ready cooperation from the Army Air Force, and Alsos used the fear to their advantage. Over 600 bombers pounded the Oranienburg site; the bombing forced several of the most senior German scientists involved in the processing of uranium to flee eastward. There they fell into the path of the Soviets, who had created an Alsos team of their own.

The Americans were soon aware of the presence of Russian atomic scientists in NKVD uniforms in Oranienburg and other targeted regions. The Soviets too captured several German scientists, including Nikolaus Riehl and Gunter Wurths, who directed the uranium processing efforts at Oranienburg. When the Soviets requested a meeting with the German scientists in Berlin shortly after capturing the city, the Germans complied. They found themselves transported to the Soviet Union shortly thereafter. As Riehl awaited transport from Berlin, Soviet operatives dismantled his temporary laboratory and sent it to the Soviet atomic weapons program site in the Soviet Union. The Soviets recovered almost 100 tons of processed uranium oxide from the Oranienburg site, an indication their own atomic weapons program had advanced further than previously suspected.

What People Don’t Know About the World War II Race for Nuclear Weapons
In the closing days of the war in Europe, post-war politics affected battlefield operations on all fronts. Wikimedia

14. The Alsos mission had to thwart its French allies to capture some of the most important German scientists

As the Allies penetrated deeper into Germany, Alsos teams advanced with them, capturing some scientists and engineers, as well as documents which led them to others. By then Germany had been sliced into occupation zones by the diplomats of the Big Four Allied nations – the United States, Britain, Soviet Union and France. Papers captured by Alsos teams in several German cities revealed several of the most pre-eminent scientists on their target lists, and a wealth of uranium and experiment results, resided in the Wurttemberg area of Germany. The region lay in the direct path of the advancing French army, which was to occupy it after the war. Groves asked Marshall in Washington to reassign the region to American troops. Marshall could not persuade the State Department to agree, unless he explained why. Concerned as ever with secrecy, Groves refused. Instead, he and Marshall turned to Eisenhower.

Groves wanted Ike to approve an American assault in the region, after which the Americans would cede the ground to the French. Alsos teams would extract what they could and destroy the rest, leaving little if anything to the French. Plans for an airborne operation, capturing an airbase for the use of the Alsos team, were scheduled for late April. Two days before the plan was to be executed the French captured an intact bridge over the Neckar River, allowing them access to the entire area in strength. With a wealth of atomic research information and several important German scientists directly in the path of the French army, Groves and American combat commanders decided on a series of ground-based hit and run raids behind the German lines. Just as Alsos had attempted to deny access to the Soviets at Oranienburg, it would do the same to French near Wurttemburg.

What People Don’t Know About the World War II Race for Nuclear Weapons
An Alsos team and support technicians dismantling a German uranium research reactor near Haigerloch in 1945. US Army

15. Alsos missions engaged German troops as they sought atomic weapons facilities

The Alsos teams advanced ahead of the French Army, behind German lines, supported by a detachment of combat engineers. The missions occurred between April 23 and May 3, 1945. They encountered German resistance, engaging the enemy in firefights as Alsos scientists investigated several atomic research sites. They discovered an intact experimental nuclear reactor which they immediately took apart and shipped back to the American lines. At Hechingen they captured more than two dozen German scientists, including the long-sought Weizsacker. Tailfingen yielded Otto Hahn, considered by many to be the prize of prizes, as well as several other important researchers. On May 1 they captured Werner Heisenberg, another physicist who had long remained elusive. A German combat group of about 700 men surrendered to the Alsos team on May 3.

As the Alsos team withdrew, Colonel Pash returned with a battalion of American troops, who took the 700 Germans into custody as prisoners of war. The Alsos team retained the captured scientists, and all the Americans withdrew to their own established zones. The French occupied the area May 4, 1945, for the most part unaware of the activity. What they did know Eisenhower explained to de Gaulle as an overextension during a combat pursuit. Eisenhower also made the decision to treat the captured German physicists and scientists as prisoners of war, but in separate facilities from combat troops and other German civilian prisoners. They were sent to Kransberg Castle, in the German state of Hesse, while plans were made on how to best exploit them and their knowledge. How to use the prisoners became the object of Operation Epsilon.

What People Don’t Know About the World War II Race for Nuclear Weapons
Farm Hall, where British and American agents secretly recorded the conversations between captive German scientists. Wikimedia

16. The Germans were dismayed to find themselves prisoners of war

All of the German scientists captured by the Alsos missions considered themselves civilians, which in fact most were. They believed themselves exempt from incarceration as prisoners of war. They also had long enjoyed special privileges in Nazi Germany, due to their preeminence in their respective fields. As prisoners, at first they received what they regarded as harsh treatments. The Allies had but recently learned of the extent of Nazi atrocities in Europe. Across the continent intensive searches for escaping Nazis and collaborators continued. Those in captivity were treated with disgust by their guards. Amenities were few, they remained under near constant observation by guards. Many were held in isolation, released only for interrogation by their Allied captors. Some expressed fear for their lives. Had they known the value the United States and Great Britain placed on their knowledge they would have likely been less fearful.

In June, 1945, after recommendation from General Groves, Eisenhower concurred with a plan to transfer 10 prominent scientists then in custody at Kransberg Castle to England. There they were to be held in relative comfort at a quiet estate. They were to be given the freedom of the grounds, mail privileges, access to personal comforts and food, and even alcohol on some occasions. The site selected to house them, an estate named Farm Hall, not far from Cambridge, underwent renovations to receive them. The renovations included the installation of audio listening and recording devices and preparation of a staff, all of whom spoke fluent German. They were provided with radios and record players, and the Alsos team developed plans for first-run movies and other forms of entertainment and recreation for their prisoners. Alsos wanted to make the Germans as comfortable as possible as they recorded their private conversations.

What People Don’t Know About the World War II Race for Nuclear Weapons
The Germans collectively expressed disbelief of the American’s success developing the atomic bomb. National Archives

17. Farm Hall revealed very little additional information on German atomic bomb research

The Germans found themselves comfortably ensconced at Farm Hall. They enjoyed considerable freedom around the house and grounds, unaware of their being continuously monitored and recorded. The recordings were on gold plated disks, which were analyzed, with transcripts prepared of conversations deemed useful. Others, mostly of a private or personal nature, were not transcribed and the disks erased. The disks were then reused. In one conversation, between Kurt Diebner and Karl Heisenberg, the subject of surreptitious listening devices arose. “I wonder whether there are microphones installed here”, said Diebner, who had administered the German atomic bomb effort. Heisenberg laughed it off, replying the British and Americans were not, “…as cute as all that”. The British kept the recording for their own amusement.

In August, 1945, the Americans used the world’s first atomic bomb over Hiroshima, followed a few days later with another, of a different design, over Nagasaki. The Germans at Farm Hall learned of the news, most of them displaying disbelief. None of the German scientists could accept the fact the Americans had been so far ahead of them in nuclear research. Otto Hahn expressed his relief that his program had failed to deliver such a weapon to Hitler in time to use it in the war. Others expressed shame at their failure, while they could not comprehend the success of the Americans, attributing it to defected Germans and in some cases to Jewish refugee physicists in the United States and Great Britain. The internment of the German physicists and chemists at Farm Hall ended on January 3, 1946, having produced about 250 pages of transcripts of information.

What People Don’t Know About the World War II Race for Nuclear Weapons
Japan’s Unit 731 and research into other WMDs led to an Alsos mission to the Pacific in 1945. Wikimedia

18. The United States implemented an Alsos mission for Japan in 1945

During the war, American intelligence agencies and the scientific community harbored little concern of the Japanese developing an atomic bomb. Japan simply lacked access to uranium needed for both research and the eventual construction of such a weapon. However, the Americans grew concerned over the Japanese use of another weapon of mass destruction, biological weapons. Alsos revealed the extent of biological weapons research by the Germans, which included documentation exchanged with the Japanese. By 1945 the Germans had an extensive inventory of biological weapons, though Hitler refused to authorize their use. The Fuhrer had himself been gassed on the Western Front during the First World War. Historians have since speculated that may have led to his refusal to deploy gas and biological weapons during the Second World War. At any rate, they had them, but did not use them against Allied troops.

The Alsos mission for Japan operated independently of those for Europe, and was originally envisioned as being part of the invasion forces planned for Japan. Deployed to Manila in the summer of 1945, the mission, entirely American in make-up, prepared to examine the Japanese biological, chemical, and nuclear programs in a manner similar to the Alsos teams in Europe. Armed support groups similar to Europe’s T-Force trained to operate with the Alsos teams. After the Japanese surrendered in September, 1945, the teams deployed to Japan and China to examine the records and interrogate the personnel of the Japanese weapons of mass destruction programs. General Groves concerned himself only with the Japanese nuclear research programs. He learned, through Alsos missions, the Japanese had assigned low priority to an atomic weapon. Lacking uranium there was little else they could do.

What People Don’t Know About the World War II Race for Nuclear Weapons
An Alsos team in France, late 1944. US Army

19. The German atomic weapon program proved much smaller than expected

When the senior scientists for the Alsos missions reviewed the scale of the German research into atomic weapons they expressed dismissal. Samuel Goudsmit, the senior scientist for the Alsos mission, personally inspected some of the German research sites, including those unearthed in Haigerloch. He wrote to General Groves of the site, describing it as “…compared to what we were doing in the United States…small-time stuff”. Later Goudsmit speculated over the usefulness of the Alsos missions, which placed numerous scientists, engineers, and support troops at considerable personal risk. “Sometimes we wondered”, he wrote, “if our government had not spent more money on our intelligence than the Germans had spent on their whole project”. The Alsos missions knew, as did Generals Groves, Marshall, and Eisenhower, the Germans were years away from an atomic bomb by 1944. However, that fact remained classified for years after the war.

Despite the heavy security surrounding the American atomic bomb, Soviet espionage agents and spy rings penetrated both the Manhattan Project and the German efforts during the war. Although the Alsos missions deprived the Soviets of several of the most notable German scientists involved, and much of their records, the Soviets acquired many others. Many of the records obtained in Alsos raids had already been copied and sent to the Soviet Union by its many agents in Germany during the war. The Soviet atomic bomb program did not really gain momentum until 1942, when the Manhattan Project’s programs were well underway. In 1949, the Soviet Union successfully detonated an atomic bomb, aided in a large part by the materials stolen from the Manhattan Project in the United States and the German efforts during World War II.

What People Don’t Know About the World War II Race for Nuclear Weapons
General Leslie Groves addressing a group of service personell at Oak Ridge, Tennessee, during the Manhattan Project. US Army

20. The Alsos missions did little to alter the course of the Second World War

If the Alsos missions revealed anything, it was the fact the Germans were years away from developing a working atomic bomb. Werner Karl Heisenberg later stated that he and many of his colleagues deliberately impeded the effort to build such a weapon out of moral considerations. Heisenberg’s recorded conversations at Farm Hall did not reveal such reticence. Instead, they blamed Germany’s failure to produce a weapon to the low priority granted the program. Though some have claimed the German atomic weapons program became Hitler’s highest priority, in fact it received little attention following 1940, since it evidently could not produce a weapon for many years to come. It received limited resources and financial support. It lacked a unified command structure. Political and personal rivalries dominated among its contributors. Alsos revealed these failings. For years those findings remained classified.

General Groves, who led the Manhattan Project for the United States, argued the Germans failed to build an atomic bomb because they never developed the industrial base needed to produce one. Lack of raw materials also contributed to the failure, as more and more dwindling supplies went to the conventional warfare needs. America’s Manhattan Project consumed about $2 billion to produce the bombs which fell on Hiroshima and Nagasaki, about $29 billion today. Germany’s atomic weapons program consumed roughly $2 million measured in 1945 dollars, less than the cost of a single U-boat. The Alsos missions did little to alter the course of the war because the Germans were never close to possessing the bomb. Alsos missions proved it beyond doubt.


Where do we find this stuff? Here are our sources:

“The Manhattan Project Interactive History”. Article, United States Department of Energy. Online

“Boris Pash”. Biography and Timeline, Atomic Heritage Commission. Online

“Hitler’s true nuclear capacity exposed in secret sabotage mission that ‘saved world'”. Callum Hoare, The Express. October 21, 2020

“Now it can be told: The True Story of the Manhattan Project”. Leslie Groves. 1962

“Hunting the Nazi Nuclear Hoard”. Sarah Reisert, Science History Institute. September 24, 2019

“Alsos Mission”. Article, Atomic Heritage Foundation. June 6, 2014. Online

“Atomic rivals and the Alsos mission”. Article, United States Department of Energy. Online

“German Atomic Bomb Project”. Article, Atomic Heritage Commission. Online

“Nazis and the Bomb”. Mark Walker, Nova. November 8, 2005

“Attacking Antwerp”. Gilbert Martin, Forbes. June 5, 2008

“German town lives with lethal legacy of World War II”. Uwe Hessler, DW Online. November 7, 2011

“Alsos mission seizes French government arsenal, September 1944”. Ruth Quinn, US Army Center of Military History. 2005

“Operation Big: The Race to Stop Hitler’s A-Bomb”. Colin Brown. 2016

“Operation Epsilon: The Farm Hall Transcripts”. Sir Charles Frank (Introduction). 1993

“Robert Furman and the Alsos Mission”. Article, Atomic Heritage Commission. Online

“Stalin and the Bomb: The Soviet Union and Atomic Energy 1939 – 1956”. David Holloway. 1994

“The Alsos Mission”. Boris Pash. 1969

“Manhattan: The Army and the Atomic Bomb”. Vincent Jones, US Army Center of Military History. 1985