The Commando Who Foiled Hitler’s Atomic Ambitions Has Died

Norwegian resistance fighter Joachim Ronneberg led the raid that destroyed stock of “heavy water” Hitler needed to produce weapons-grade plutonium

A statue in Joachim Ronneberg's honor stands tall outside the city hall in Alesund Richard Cummins / Alamy Stock Photo

In the television adaptation of Philip K. Dick’s alternative history novel, The Man in the High Castle, the Nazi regime is able to take over North America because it develops and uses the atomic bomb before the United States. While that is fiction, there was a proto-nuclear arms race going on between the Allies and the Axis powers. Luckily for the Allies, they had the talents of Norwegian resistance fighter Joachim Ronneberg at their disposal, who led a raid in his home country that set back the Nazi nuke program. As Bill Chappell at NPR reports, the Norwegian national hero has died at the age of 99.

“He is one of our great heroes,” Norway's Prime Minister Erna Solberg tells the Norwegien news agency NTB. “Ronneberg is probably the last of the best-known resistance fighters to pass away.”

Ronneberg fled Norway in 1940 after the Germans invaded the Scandinavian nation. He ended up in Great Britain, where he trained with the Special Operations Executive, a secret force that taught resistance fighters military skills and guerrilla war tactics.

In 1942, British intelligence services learned that the Germans were planning to use so-called heavy water to develop plutonium, an element necessary for creating atomic weapons. The most available source was Norsk Hydro’s Vemork plant, outside Rjukan in Tinn, Norway, which had been producing heavy water for fertilizer since 1934. The Brits sent in a 35-man commando team to disable the factory, but the attack was a dismal failure.

In 1934, they tried again, this time tapping 23-year-old Lieutenant Ronneberg to lead a smaller team of ten for the high-risk operation, codenamed Gunnerside. Many considered it to be a suicide assignment, and the team carried cyanide capsules with them, ready to die rather than be captured.

The raid was delayed for weeks by blizzards. Then, finally, on February 28, the team parachuted into the mountains surrounding the plant, landing off target, in what is now Telemark National Park. They broke inside the hydro plant in the dark of night. As Erin Blakemore at reports, a door that a Norwegian collaborator was supposed to have left open was shut tight. Instead, Ronneberg and a few men squeezed through a cable shaft to get inside the heavy water facility. The saboteurs subdued a workman and set to work attaching explosives to the storage tanks for the heavy water.

To ensure their success, Ronneberg decided to cut the fuses on the explosives down from several minutes to just 30 seconds, meaning the team would barely have time to escape to a safe distance. But they made it, hearing a muffled thump behind them as 1,100 pounds of heavy water literally went down the drain, as the equipment used to extract the isotope was destroyed.

That was not the most harrowing part of their mission. After the raid, 2,800 German soldiers began scouring the countryside looking for the commandos. Luckily, the Norwegian team had a secret-weapon: their national sport. They swiftly cross-country skied through the mountains for the next two weeks, making a 280-mile marathon run to the Swedish border where Ronneberg and his team presented themselves as refugees to avoid suspicion. Ronneberg once joked to the BBC that it was “the best skiing weekend I ever had,” according to Chappell of NPR.

Ronneberg went on to lead other missions during the war, but Operation Gunnerside was by far the most well-known. He was lionized in the 1965 Kirk Douglas film The Heroes of Telemark and in a 2015 mini-series called The Heavy Water War. Though he received many awards for his bravery, Ronneberg rarely spoke about the raid, and he worked as an advocate for peace in the 1970s. He spent his career at the Norwegian public broadcasting company NRK, serving as a reporter and broadcast director.

At the time of the raid, the little band of commandos did not really know the significance of their mission. They only learned the true meaning of their contribution after the U.S. dropped atomic bombs on Japan. “That was in August of 1945, when they dropped the bombs on Hiroshima and Nagasaki,” Ronneberg told the BBC, “…then we knew that what we had done had been of great importance. But not until then.”

It’s estimated that Gunnerside destroyed five months-worth of heavy water and crippled the mechanism for producing it. It took over four months for the plant to become operational again, and soon after that Allied bombers pulverized the hydro station. In 1944, Hitler tried to bring heavy water production to Germany, but Norwegian saboteurs sunk the ferry that was carrying the remaining heavy water and production machinery across the North Sea. Without the heavy water, and with D-Day on the horizon, the German effort to create a nuclear weapon fizzled.

Even with the heavy water, Reuters reports that historians still debate whether the Nazis had enough time and resources to develop an atomic weapon. Whatever the case, Ronneberg's heroic “skiing weekend” made sure they never got the chance to try.

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