On November 26, 1944, American physicist Samuel Goudsmit led Operation Alsos into Strasbourg, France, searching the apartment of German virologist Eugen Haagen. Working alongside biological warfare experts Bill Cromartie and Fred Wardenberg, Goudsmit sought to determine how close Nazi Germany was to deploying atomic, biological, or chemical weapons. Having recently learned the German atomic program had failed, Alsos now focused on biological threats.

Reading through Haagen’s correspondence, Goudsmit discovered a November 1943 letter requesting additional concentration camp prisoners for experiments. This revealed Nazi doctors were testing deadly vaccines on humans. Because biological weapons required protective vaccines for the attacking nation’s forces, Goudsmit recognized this research’s military purpose. The documents identified two key targets: Kurt Blome, deputy surgeon general overseeing biological weapons, and Walter Schreiber, surgeon general responsible for vaccines.

On December 9, 1944, at Castle Varlar in Germany, Major General Walter Dornberger and physicist Wernher von Braun celebrated the V-2 rocket program. Albert Speer, Hitler’s armaments minister, presented Knight’s Cross medals to scientists while V-2s launched toward Antwerp. Days later, one rocket struck a crowded cinema, killing 567 people. Later, General Eisenhower acknowledged that earlier deployment of the V-2 could have changed the course of the war.

The V-2s were assembled in underground tunnels at Nordhausen by enslaved concentration camp laborers working under production director Arthur Rudolph and general manager Georg Rickhey. Approximately 60,000 prisoners were brought to the facility, where about half were worked to death under traumatic conditions. The SS Business Administration Main Office, partnering with Speer’s ministry and corporations like IG Farben, managed this network.

On May 6, 1944, Rickhey, von Braun, Dornberger, and Rudolph met to procure 1,800 more enslaved French workers. In August, von Braun personally visited Buchenwald to select prisoners for a new laboratory. By December 1944, while celebrating their achievements, these men relied entirely on forced labor to maintain production.

On December 31, after witnessing hundreds of dead German soldiers in Belgium, Speer concluded the war was lost. He fled to Schloss Kransberg before visiting Hitler at Adlerhorst on New Year’s Day, where Hitler’s optimism temporarily revived Speer’s confidence. On January 15, Hitler moved permanently into the Berlin Führerbunker. Speer was sent to survey factories in Poland, where he witnessed the devastated Wehrmacht and learned from Field Marshal Schörner that Soviet forces would soon overrun the area. On January 30, 1945, Speer wrote a memo to Hitler that began by declaring the war was lost.

On January 17, 1945, as Soviet forces approached, chemist Otto Ambros and colleague Walther Dürrfeld destroyed documents at IG Farben’s Auschwitz facility. Ambros managed IG Auschwitz, the corporation’s synthetic rubber and fuel factory that operated by using enslaved laborers. Survivor Gerhard Maschkowski recalled the chaos as SS guards burned evidence and prepared death marches. On January 18, 9,000 emaciated prisoners began marching west; 60% died within two days. Primo Levi, a prisoner-chemist hospitalized with scarlet fever, stayed behind and witnessed the Red Army’s liberation on January 27. Ambros had already departed on January 23, heading to another Farben facility at Falkenhagen to destroy more evidence.

Simultaneously, at Dyhernfurth in Poland, IG Farben operated a massive underground complex producing the deadly nerve agent known as tabun. On February 5, as Russian forces captured the area, Major General Max Sachsenheimer led 82 scientists and commandos back into the facility to remove all traces of tabun. Under cover of diversionary attacks, the team successfully scrubbed the plant and escaped. The Soviets discovered the intact-but-empty facility, shipped it to Beketovka, and began their own tabun production. The nerve agent plant at Dyhernfurth had been designed and managed by Otto Ambros.

During this time, Hitler issued the Nero Decree, ordering total destruction of German infrastructure. At Nordhausen, conditions deteriorated as death marches from eastern camps flooded the tunnels. Von Braun pushed to increase rocket production despite mass starvation. Following a failed uprising by the prisoners, the ringleaders were hanged from an industrial crane as an example to compel the others not to rebel.

On March 12, von Braun survived a serious car accident that broke his arm. While recuperating, he instructed aide Dieter Huzel and colleague Bernhard Tessmann to hide classified V-2 documents as leverage to be used with the Allied forces. On April 1, SS General Kammler evacuated 500 key scientists to Bavaria. On April 4, Huzel and Tessmann hid dozens of document crates in the Dörnten mine and dynamited the entrance. They informed Karl Otto Fleischer, the Mittelwerk’s business manager, of the location before fleeing south.

In late March 1945, Operation Alsos prepared to raid IG Farben factories. British Field Marshal Bernard Montgomery’s Operation Plunder, a massive Rhine crossing that opened over 500 miles of the western front, triggered an intelligence free-for-all as groups from the United States and Britain sought out research and scientists. Alsos reached Ludwigshafen first, but found the bombed Farben factory stripped of documents. The CIOS chemical weapons team, led by American Lieutenant Colonel Philip Tarr and British Major Edmund Tilley, arrived soon after, revealing a rivalry between Allied countries. Both teams sought the mysterious nerve agent tabun. At other Farben locations, captured scientists lied about their work, claiming only to produce civilian goods.

A major breakthrough came in Bonn, where a Polish lab technician salvaged classified documents a professor had attempted to flush. These papers led to the Osenberg List: a comprehensive directory of 15,000 German scientists compiled by Dr. Werner Osenberg for the Reich Research Council. Alsos captured Osenberg and his complete card catalogue, sharing this intelligence goldmine with CIOS. When interrogated at Versailles, Osenberg insisted he was merely second in command of the Gestapo’s scientific section and revealed the location of additional documents.

In Berlin, Colonel Siegfried Knemeyer, chief of Luftwaffe technical developments, worked at the Air Ministry as the city crumbled. Speer tasked him with hiding Luftwaffe documents and planning an escape to Greenland. Knemeyer recruited fellow pilot Werner Baumbach, who secured a long-range BV 222 aircraft and gathered supplies. On April 20, Hitler’s birthday, Baumbach received a warning from SS-Brigadeführer Walter Schellenberg about an impending arrest. Baumbach and Knemeyer fled to Travemünde airfield, where Himmler summoned Baumbach to discuss the use of the aircraft for potential Allied negotiations. Meanwhile, Speer made a final visit to Hitler in the Führerbunker, where Hitler’s cold dismissal convinced Speer their relationship had ended.

On April 11, 1945, the US 104th Infantry Division entered Nordhausen’s facility. Private John Risen Jones photographed hundreds of corpses and dying prisoners. War crimes investigator William Aalmans found a single document left behind at the facility—the Mittelwerk telephone directory—listing Georg Rickhey and Arthur Rudolph as production leaders.

Allied forces discovered similar facilities across Germany. In Geraberg, soldiers found a concealed biological research laboratory which Alsos expert Bill Cromartie determined was designed for vaccine production. A villager led them to equipment belonging to Dr. Karl Gross, who worked under Dr. Kurt Blome, placing Blome atop the biological weapons target list.

On April 13, American troops stumbled upon the Hermann Göring Aeronautical Research Center at Völkenrode, an advanced aeronautics facility previously unknown to the Allies. Scientific director Adolf Busemann showed them wind tunnels where German scientists had already breached the sound barrier. Colonel Donald Putt of Operation Lusty recognized the facility’s revolutionary capabilities and proposed bringing both equipment and scientists to America. His superior, Major General Hugh Knerr, urged the War Department to overlook the scientists’ Nazi Party membership for national security purposes. The equipment received immediate approval for transfer, but hiring scientists required more time.

On April 16, British forces discovered the Raubkammer proving ground and nearby bunker complexes containing 100,000 mustard gas shells and 175 bunkers filled with unknown munitions bearing three green rings. CIOS experts tested the substance on rabbits and discovered it killed five times faster than any known agent. This was tabun, Hitler’s secret nerve agent, never deployed during the war.

In Berlin on April 20, Dr. Walter Schreiber performed emergency surgeries in a subway tunnel while Hitler’s inner circle celebrated his birthday. That day, Speer flew into encircled Berlin. Inside the bunker, he encountered Martin Bormann, Joseph and Magda Goebbels, and Eva Braun before Hitler’s dismissive farewell. On April 29, American forces liberated Dachau. Army physician Dr. Marcus Smith arrived the next day, discovering 32,000 starved, diseased survivors and a smashed laboratory in Experimental Cell Block Five, where prisoners revealed Nazi doctors had performed lethal medical experiments.

On April 30, 1945, Hitler died by suicide as Soviet forces closed in. Red Army soldiers captured Dr. Walter Schreiber while British troops arrested Siegfried Knemeyer. Wernher von Braun and Walter Dornberger, confident of their value, orchestrated their surrender from a Bavarian ski resort. Seven rocket scientists, including Wernher and Magnus von Braun, Dornberger, Herbert Axster, Hans Lindenberg, Dieter Huzel, and Bernhard Tessmann, surrendered to the US Counter Intelligence Corps. American officers noted von Braun’s arrogance and lack of remorse as he demanded to see Eisenhower and claimed sole credit for inventing the V-2.

In Heidelberg, CIOS investigator Major Edmund Tilley located IG Farben CEO Hermann Schmitz. Searching Schmitz’s study, Tilley discovered a hidden safe containing a photo album chronicling the history of IG Auschwitz, though the significance of Auschwitz remained unknown to most Allies in May 1945.

In Gendorf, Dr. Otto Ambros successfully deceived American soldiers by presenting himself as a civilian chemist managing a detergent factory. On May 17, authorities arrested Dr. Kurt Blome in Munich. Initially cooperative, Blome admitted witnessing the mass gassing of Jews. In subsequent interrogations with Major E. W. B. Gill, however, he became completely evasive, claiming organizational complexity prevented him from explaining his duties or identifying colleagues. Gill concluded Blome was a liar.

Colonel Peter Beasley of the US Strategic Bombing Survey tracked down Georg Rickhey and offered to recommend him for American employment in exchange for knowledge about underground weapons facilities. Rickhey agreed and was taken to London to translate documents.

On May 23, British forces arrested Albert Speer at Schloss Glücksburg. Speer boasted about underground facilities while dismissing his involvement in war crimes. That same day, Heinrich Himmler revealed his identity to Captain Thomas Selvester at an interrogation camp, then bit a hidden cyanide capsule during the examination, dying by suicide.

With the war over and no official policy established, the captured scientists’ fates remained uncertain. One officer observed that determining who qualified as a Nazi was a difficult question.