US Army Air Forces physicians Major General Malcolm Grow and Lieutenant Colonel Harry Armstrong devised a plan to exploit Nazi aviation research. Armstrong traveled to Berlin in search of Luftwaffe doctors, particularly Dr. Hubertus Strughold, whom Armstrong knew from prewar medical conferences. Through Dr. Ulrich Luft, Armstrong learned that Strughold and his staff were working in Göttingen under British control.

Simultaneously, Major Leopold Alexander, a Boston-based psychiatrist and war crimes investigator, was also searching for Strughold, whose name appeared on the list of suspected war criminals. Alexander, a Jewish physician who had fled Germany in 1933, was tasked with investigating Nazi medical crimes. His background made the assignment deeply personal: His father had been murdered in 1932 and his former mentor, Karl Kleist, had assisted the Nazi regime. Alexander’s investigation began at Dachau, where he interviewed Dr. Georg August Weltz about research on reviving frozen pilots. Weltz claimed experiments were conducted on animals, but Alexander discovered two wooden tubs sized for human beings. In Göttingen, Strughold insisted that only a deceased fringe doctor named Sigmund Rascher had conducted human experiments at Dachau.

Alexander’s breakthrough came when he examined Heinrich Himmler’s secret files in Heidelberg. The documents revealed that Dr. Siegfried Ruff, Strughold’s close colleague, had overseen Rascher’s experiments. Photographs showed another Strughold colleague, Dr. Ernst Holzlöhner, holding prisoners down in tubs of icy water as their body temperatures were recorded while they died. At Dachau, survivors testified that experiments in Cell Block Five killed most subjects; code words like “large pigs” (129) referred to human beings. Alexander concluded that Strughold was covering up war crimes.

Despite Alexander’s findings, Allied officers wrote sympathetic reports about the Luftwaffe doctors, praising their research. The Army Air Forces made a deal with Strughold to co-chair a secret research center in Heidelberg, where he handpicked 58 Luftwaffe doctors—including war crimes suspects Ruff, Benzinger, and Schäfer. Only Weltz was arrested for trial at Nuremberg.

In Washington, the State-War-Navy Coordinating Committee debated the controversial Nazi scientist program. The State Department opposed it, citing hypocrisy. Opposition existed in the War Department itself: Secretly recorded conversations revealed unease about treating enemy scientists as honored guests. Undersecretary of War Robert Patterson appointed John J. McCloy to mediate the disputes. McCloy, who saw scientists and war criminals as distinct categories, simultaneously coordinated the recruitment program and helped develop war crimes prosecutions.

John Dolibois was a G-2 intelligence officer who had spent months at Camp Ritchie teaching classes on the Nazi hierarchy using the propaganda film Triumph of the Will. Dolibois finally received his assignment to Europe in April 1945. After witnessing the devastation of postwar Europe and searching for disguised Nazis at Dachau, he was sent to a mysterious facility identified only as CCPWE No. 32. Dolibois arrived at the Palace Hotel in Mondorf-les-Bains, Luxembourg—the country of his birth, which he had not seen in 14 years. The former spa was now a heavily fortified prison codenamed Ashcan, holding high-ranking captured Nazis. Shortly after his arrival, Dolibois was confronted by Hermann Göring about prisoners’ conditions. Dolibois seized the opportunity to gain the prisoners’ confidence.

Ashcan housed the Nazi “Bonzen” (140), the high ranking Nazis such as Hans Frank, Wilhelm Keitel, Alfred Jodl, Karl Dönitz, Albert Kesselring, Joachim von Ribbentrop, Albert Speer, Robert Ley, Julius Streicher, Alfred Rosenberg, Arthur Seyss-Inquart, and Wilhelm Frick. Dolibois studied their fears and obsessions, finding them eager to talk and to shift blame. He used cross-examination to play prisoners against each other, though determining truth from lies remained challenging.

The US Chemical Warfare Service aggressively pursued Nazi nerve agent technology. By mid-May 1945, analysts confirmed that tabun was a revolutionary weapon. Despite State Department opposition to admitting German chemists, the service prioritized acquiring both the science and the scientists. At the Allied interrogation center codenamed Dustbin, IG Farben chemist Dr. Gerhard Schrader revealed how he had accidentally discovered tabun in 1936 while developing pesticides. Tests showed the substance could kill a healthy ape in 16 minutes through inhalation. The Reich immediately classified it and ordered mass production. Schrader directed interrogators to Dr. Otto Ambros, who had managed full-scale production.

Through interrogations of Farben board members Karl Krauch and Baron Georg von Schnitzler, Allied investigators learned that Ambros had overseen chemical weapons plants at Gendorf and Dyhernfurth, which also produced an even deadlier nerve agent called sarin. Ambros had also managed IG Farben’s synthetic rubber factory at Auschwitz, built on a deal between Farben and the SS to exploit concentration camp labor. Von Schnitzler admitted that Farben directors (including Ambros) knew the company’s Zyklon B gas was being used for mass murder.

When ordered arrested, Ambros vanished. In fact, he was removed by Lieutenant Colonel Philip Tarr of the US Chemical Warfare Service, who sent Ambros on an unsupervised mission to retrieve nerve gas production blueprints. Local Counter Intelligence Corps agents seized the documents and Ambros fled to the French zone, where he secured employment at a Farben plant in Ludwigshafen. A meeting between Ambros, Tarr, and Dow Chemical representative Dr. Wilhelm Hirschkind revealed that some US officials prioritized acquiring chemical weapons knowledge over prosecuting war criminals. Despite the efforts of FIAT (Field Information Agency, Technical), Ambros remained free.

Dr. Kurt Blome was also interrogated regarding the Reich’s biological weapons program. Blome claimed Heinrich Himmler drove the program and ordered him to experiment on humans to develop plague vaccines. He described Himmler’s schemes to spread plague and cattle diseases, and revealed that both his plague institute and veterinarian Dr. Erich Traub’s laboratory had been captured by the Soviets, along with Major General Dr. Walter Schreiber, who managed defensive vaccine programs.

The future of captured Nazi scientists hung in the balance between prosecution and recruitment. During the interrogations at Ashcan, Colonel Burton Andrus grew frustrated as prisoners conspired to withhold information. He screened a graphic Buchenwald atrocity film, hoping to pressure confessions. Walter Funk tearfully admitted ordering gold extracted from concentration camp victims’ teeth, though he later denied the conversation. Andrus devised an eavesdropping operation, moving four prisoners to a house wired with hidden microphones, but the project yielded little information.

John Dolibois transported 33 prisoners from Ashcan to Oberursel. On the return journey, Dolibois encountered trucks hauling thousands of decomposing Dachau corpses for reburial. The experience solidified his conviction of Nazi guilt. He then flew the final Ashcan prisoners, including the dangerous Ernst Kaltenbrunner, to Nuremberg. Handcuffed to Dolibois during the flight, Kaltenbrunner attempted to justify his actions by claiming he only followed orders.

On July 6, 1945, the Joint Chiefs of Staff formally approved Operation Overcast without President Truman’s knowledge. The program stipulated temporary employment for scientists who were not known war criminals. The British conducted Operation Backfire rocket tests with von Braun and Arthur Rudolph, but refused to return General Dornberger, sending him to a POW camp instead.

On September 20, 1945, the first 16 German scientists arrived at New Castle Airport, Delaware. They were processed at Fort Strong, an island in Boston Harbor that the unhappy scientists nicknamed “Devil’s Island.” Major James Hamill escorted von Braun by train to Fort Bliss, Texas.

Meanwhile, the pursuit of Otto Ambros intensified. FIAT’s Major Tilley learned from Ambros’s deputy, Jürgen von Klenck, about a steel drum of hidden documents. After a two-month search, Tilley found the cache on October 27, containing hard evidence of nerve agent contracts, Ambros’s destruction orders, and plans for chemical weapons production at Auschwitz. On January 17, 1946, Ambros was finally arrested outside the French zone and sent to Nuremberg to await trial.