Stuff You Should Know: WWII Sabotage Spotlight: Operation Gunnerside

Episode Release Date: January 14, 2025

Hosts: Chuck Bryant and Josh Clark

Introduction

In this gripping episode of Stuff You Should Know, hosts Chuck Bryant and Josh Clark delve into one of World War II's most daring and impactful sabotage missions: Operation Gunnerside. Despite its critical role in delaying the Nazi atomic bomb project, Operation Gunnerside remains relatively obscure, especially outside of Norway. This episode uncovers the meticulous planning, courageous execution, and enduring legacy of the Norwegian resistance fighters who undertook this high-stakes mission.

Background: The Race for the Atomic Bomb

Heavy Water and Its Significance

The story begins in 1939 when German physicists discovered that splitting the atom through nuclear fission could release immense energy. This breakthrough sparked a global race to harness nuclear energy, with both the Allies and the Nazis vying to develop atomic bombs. Central to this endeavor was heavy water (deuterium oxide), a crucial moderator in nuclear reactors that slows down neutrons to sustain a controlled nuclear reaction. Unlike regular water (H₂O), heavy water (D₂O) contains deuterium, a hydrogen isotope with an additional neutron, making it significantly heavier.

The Vemork Norsk Plant in Norway

Located in Telemark, Norway, the Vemork Norsk heavy water plant was the world's leading producer of heavy water. Chemist Leif Tronstad spearheaded efforts to maximize production, extracting the scarce heavy water from vast quantities of mountain water, a process both resource-intensive and technologically challenging. As Josh Clark aptly puts it, "[...] they were separating out this 1 in 20 million molecule of heavy water from regular mountain water."

Nazi Occupation of Norway

In April 1940, Nazi Germany invaded Norway, overriding the country's declared neutrality. The occupation led to the establishment of a Nazi-controlled government, prompting widespread resistance among the Norwegian populace. Many Norwegians chose to join the underground resistance, aiming to undermine the Nazi war machine from within. Among them was Leif Tronstad, who recognized the strategic importance of the Vemork plant in thwarting the Nazi atomic ambitions.

Early Sabotage Efforts: Operation Grouse and Operation Freshman

Operation Grouse: Laying the Groundwork

Chuck Bryant highlights, "Operation Grouse was the initial attempt to establish a foothold in Norway for the upcoming sabotage missions." This operation involved parachuting a team of trained saboteurs into the Norwegian wilderness to set up a base camp and prepare for more extensive missions. However, the team faced severe challenges due to Norway's harsh winter conditions, leading to difficulties in assembling the necessary resources for a successful attack on the heavy water facility.

Operation Freshman: A Costly Misstep

Building upon the groundwork laid by Operation Grouse, the Allies launched Operation Freshman—a mission involving two air gliders carrying 39 British soldiers into Norway. The objective was to provide additional muscle and support to the resistance fighters. Tragically, the mission was a disaster. One glider crashed into a mountain, killing everyone on board, while the other veered off course and crashed upon landing, resulting in the Gestapo capturing and executing the survivors. Moreover, the crash revealed a crucial map indicating the saboteurs' intended target—the Vemork plant. As Josh Clark summarizes, "[...] the Gestapo found the survivors and executed them basically on the spot."

Operation Gunnerside: The Daring Sabotage Mission

Recruitment and Training of Saboteurs

Undeterred by the failures of previous operations, the Allies sought a more streamlined and effective approach to thwart the Nazi atomic program. Enter Operation Gunnerside—a meticulously planned mission led by Norwegian resistance fighter Jens Anton Poulsen. Recognizing the need for a small, highly skilled team, Poulsen and his comrades underwent rigorous training under the auspices of the Special Operations Executive (SOE), Britain's elite sabotage organization. According to Josh Clark, "They trained saboteurs to operate in extreme weather and challenging terrains, preparing them for the unforgiving Norwegian winters."

Deployment and Journey to Vemork

On February 27, 1943, a team of nine Norwegian saboteurs, including Poulsen and Frederick Kaiser, parachuted into the remote Norwegian countryside. Their mission: infiltrate the heavily guarded Vemork plant and destroy the heavy water production capabilities. Facing treacherous snowy landscapes, the team embarked on a grueling five-day trek, often skiing through isolated regions to reach their target. Chuck Bryant remarks, "They skied about 200 miles, which is like nothing for them."

The Sabotage Operation

Upon reaching the Vemork plant, the team split into smaller groups to maximize efficiency and minimize the risk of total mission failure. Entrenching themselves within the facility, they methodically planted explosives on key infrastructure components. As the tension mounts, with Nazi guards monitoring their every move, the saboteurs prepared to detonate the charges. In a critical moment, Runner Frederik Kaiser compelled a Norwegian watchman to assist by offering chloroform to render him unconscious, ensuring the team's undisturbed execution of the mission.

At exactly 3:30 AM, Poulsen detonated the explosives, not waiting for the two-minute fuse to run out, exemplifying his unwavering commitment: "He said, no, I really want to make sure we hear this thing go off. So we're gonna go down to 30 seconds." Despite their efforts, the explosion was modest, shattering only a window and causing minimal immediate damage. Nevertheless, the strategic impact was profound. Josh Clark notes, "The plant was put out of operation, halting heavy water production and delaying the Nazi atomic bomb project."

Escape and Aftermath

Miraculously, all nine saboteurs evaded capture, escaping into the Norwegian wilderness with remarkable agility. Their successful infiltration and sabotage underscored the effectiveness of the operation, even in the face of tight security and adverse conditions. The mission not only deprived the Nazis of a critical resource but also served as a morale booster for the Allied forces and the Norwegian resistance.

Subsequent Operations: Further Sabotage and Allied Bombing

Resumption of Heavy Water Production

Despite the success of Operation Gunnerside, the Nazis swiftly endeavored to restore heavy water production. By May 1943, just a few months after the sabotage, the Vemork plant had ramped up operations to full capacity. Recognizing the need for continued interference, the Allies devised additional sabotage missions to ensure the longevity of the heavy water disruption.

Operation Sunshine and Tragic Losses

Leif Tronstad, now an integral figure in the resistance, led Operation Sunshine in October 1944. This mission aimed to protect Norway's industrial assets from remaining Nazi saboteurs as the war drew to a close. Tragically, Tronstad was killed in May 1945 by a collaborator’s brother, underscoring the personal risks undertaken by those involved in the resistance.

Sabotage of the Hydro Ferry

In February 1944, the Norwegian resistance launched another critical operation targeting the ferry Hydro, which was responsible for transporting heavy water shipments to Germany. Under the leadership of Julius Poulsen, the team attached explosive charges to the ferry's bow, successfully sinking the vessel and destroying a significant portion of the heavy water cargo. As Josh Clark explains, "Allied intelligence confirmed that the sabotaged ferry carried heavy water, thereby inflicting a substantial blow to the Nazi atomic program."

This operation resulted in the loss of 14 Norwegian civilians and four German soldiers, a somber reminder of the human cost associated with war efforts. However, the strategic gain was undeniable, crippling the Nazi access to heavy water and further stalling their atomic ambitions.

Impact and Legacy: Shaping the Course of the War

Delaying the Nazi Atomic Bomb

Chuck Bryant emphasizes the strategic importance of these sabotage missions: "Even in retrospect, not a single bullet was fired and not a single person died in this highly successful, amazingly daring sabotage operation." The cumulative effect of Operation Gunnerside and subsequent missions significantly hindered the Nazis' ability to produce heavy water in sufficient quantities, thereby delaying their atomic bomb project by several crucial months.

Historical Debates and Interpretations

Despite the clear successes of these operations, historians continue to debate the overall impact on the war's outcome. While the official SOE historian, M.R.D. Foot, asserts that these actions "changed the course of the war," others argue that the Nazi atomic program was never as advanced as feared, particularly due to internal scientific miscalculations and the loss of key scientists. For instance, Chuck Bryant points out, "The Nazis regretted pursuing heavy water instead of graphite as a moderator, which was a critical miscalculation."

Representation in Media

Operation Gunnerside has inspired several portrayals in film and television, though often with varying degrees of historical accuracy. The 1965 film The Heroes of Telemark starring Kirk Douglas offers a dramatized account of the mission, blending factual events with fictional elements. More recently, the Norwegian state broadcaster NRK produced the miniseries Heavy Water War in 2015, bringing renewed attention to the operation within Norway and internationally.

Conclusion

Operation Gunnerside stands as a testament to the courage, ingenuity, and resilience of the Norwegian resistance during one of history's most tumultuous periods. Through meticulous planning and unwavering dedication, the saboteurs successfully crippled the Nazi heavy water production, indirectly contributing to the Allied victory and the shaping of the post-war world. Chuck Bryant and Josh Clark's exploration of this operation not only sheds light on a pivotal yet underappreciated chapter of World War II but also honors the legacy of those who risked their lives for the greater good.

Notable Quotes with Timestamps

• Josh Clark [03:45]: "Nazi atomic bomb was among the most frightening combination of words you could possibly come up with."

• Chuck Bryant [05:10]: "Heavy water is really, really rare. And it takes a long time to get just a little bit of it."

• Josh Clark [09:56]: "Tronstad was like, we've got ammonia tanks there. Liquid ammonia. You're definitely gonna kill a bunch of civilians nearby."

• Chuck Bryant [24:23]: "I love this kind of thing. It's just the kind of thing."

• Josh Clark [31:02]: "Snip, snip. So that paid off pretty quickly."

• Chuck Bryant [37:28]: "That's right. But that is not the end of the story."

• Josh Clark [44:37]: "The Nazis regretted pursuing heavy water instead of graphite as a moderator."

Acknowledgments

A special thanks to Matthew Maimault Bouchard for recommending Operation Gunnerside as a topic, ensuring that Stuff You Should Know continues to explore and illuminate the lesser-known yet profoundly impactful events of history.

For more insightful episodes and detailed explorations of fascinating topics, subscribe to Stuff You Should Know on the iHeartRadio app, Apple Podcasts, or your preferred podcast platform.