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Sabotaging Hitler's Heavy Water
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Michael Dilley Articles
Review: Invasion Syria 1941
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Force At La Difensa
Sabotaging Hitler's Heavy Water
The Return of Rogers' Rangers

Michael Dilley Books

Behind the Lines: A Critical Survey of Special Operations in World War II

Galahad: A History of the 5307th Composite Unit (Provisional)

Elite Warriors: 300 Years of America's Best Fighting Troops

Sabotaging Hitler’s Heavy Water
By Michael F. Dilley

The years leading up to and including World War II saw a race by Germany and the United States to develop an atomic weapon. Although the idea of nuclear fission was first mentioned in 1934, it was not until four years later that experiments confirmed it by using Uranium. The two methods for moderating the energy of neutrons loosed by bombarding Uranium involve the use of heavy water or graphite. Heavy water, or Deuterium, which looks like regular water, was discovered in 1933. Germany ultimately decided to use heavy water in its nuclear reactor to breed the Plutonium-239 needed in its weapons research.

One method of producing heavy water is by separating it from regular water using electrolysis. This method requires electrolysis chambers and a considerably large amount of power. Ultimately the heavy water supplier for scientists throughout the world was the hydroelectric plant run by Norsk Hydro, located near Rjukan in the Telemark region of Norway.

By late January 1940, Germany had begun procuring heavy water from Norsk Hydro through the firm of IG Farbenindustrie Aktiengesellschaft. At about the same time the French Military Intelligence organization, Deuxieme Bureau, conducted an operation to remove what was then the world’s supply of heavy water from Norsk Hydro. This amounted to about 44.25 gallons. In a risky operation the heavy water was removed from Norway and sent, ultimately, to Falmouth, England by a roundabout route (Oslo to Perth, Scotland to Paris to Bordeaux to Falmouth).

Despite this removal, Allied commands and intelligence organizations believed that the Germans would use Norsk Hydro to continue its heavy water production operations to produce a sufficient supply for use in their weapons research program. British Special Operations Executive (SOE), charged with conducting, among other operations, sabotage campaigns, began planning several operations aimed at limiting or destroying heavy water production at Norsk Hydro.

The first phase, codenamed Operation Grouse, was conducted on the night of 18-19 October 1942. In this operation, four Norwegians (Knut Haugland, Arne Kjelstrup, Jens-Anton Poulsson, and Claus Helberg) parachuted onto the Hardanger plateau, which was above and near the Norsk Hydro plant. Their mission was to gather as much intelligence (including blueprints, if possible) concerning the plant and its heavy water operations.

The information the Grouse team obtained was sent back to SOE for use in planning the next phase of operations. This phase was codenamed Operation Freshman. For this operation a force of sappers (combat engineers), all paratroopers of the British 1st Airborne Division, were sent in by gliders to link up with the Grouse team. The combined teams were to set and detonate demolitions in key parts of the Norsk Hydro plant to destroy its heavy water capability, then escape and evade through Norway to Sweden. The Freshman team left England on the night of 19 November 1942.

Weather conditions in the vicinity of the designated drop zones on that night were extremely poor. As a consequence, the link up of the two teams did not take place. One of the Halifax bombers towing a glider crashed into a mountain, killing its entire crew. Shortly before, the glider attached to this tug was able to detach itself but crash landed, resulting in many casualties among the sappers. The other glider also crash landed, killing most of its occupants. The second Halifax limped back to England and landed safely. All of the surviving sappers were captured by the Germans, tortured, interrogated, and eventually murdered. This was in keeping with what was called The Commando Order, issued by Adolf Hitler on 19 October 1942. The Commando Order stated that all Allied commandos that German forces captured would be killed immediately, regardless whether they were in uniform or tried to surrender. Failure to carry out this order was considered an act of negligence by German military law.

Because of the Freshman operation, the Germans became aware of Allied interest in the heavy water operations at Norsk Hydro. Plans were immediately put into effect to upgrade the perimeter defenses at the plant. This included establishing a mine field around the plant, putting in floodlights on the perimeter, and increasing the size of the guard force. The increased security did not deter SOE.

Planners searched for another way to send in commandos to link up with the Grouse team, which by now had been renamed the Swallow team. The four commandos of Swallow team lay low for several months in the mountains above the hydro plant, continuing to maintain contact with SOE in London by radio. They subsisted as best they could on whatever was available. One report states that they were able to kill a reindeer in late December 1942.

SOE finalized the plans for the next phase, codenamed Operation Gunnerside. In this phase, six additional Norwegian commandos (Joachin Ronneberg, Knut Haukelid, Fredrik Kayser, Kasper Idland, Hans Storhaug, and Birger Stromsheim) parachuted into Norway on the night of 16-17 February 1943. Several days later the Gunnerside team linked up with the Swallow team and they began planning for their assault on the plant. They decided to attack on the night of 27-28 February 1943.

In the intervening months after the failed Operation Freshman, security had become somewhat slacker. The lights and mine field remained in place but the guards had become complacent. Nevertheless, the only bridge spanning the 246 feet long ravine over the Maan River, was still guarded at full strength. Because of this, the combined teams decided that their best approach was to climb down the 656 feet deep ravine, cross the icy river, and then climb up the other side of the steep ravine. Using the information obtained about the plant layout, the teams found and followed a single rail line into the plant area without being detected by any of the guard force.

Once inside the plant itself, the teams encountered a Norwegian caretaker who assisted them in their subsequent movement in the plant. The teams moved quickly to the area where the heavy water electrolysis chambers were located and put their explosives in place. A long time-delay fuse was attached to the explosives and the teams prepared to light it and leave. They left behind a British submachine gun, hoping the Germans would draw the conclusion that the sabotage was the work of British forces. They hoped this would prevent any German reprisals taking place directed at local citizens. Just as they were ready to light the fuse, the caretaker stopped them; he could not find his eyeglasses! Since eyeglasses were very difficult to get, the commandoes conducted a search of the area and found them. They then lit the fuse and left the plant the same way they had entered.

After they were clear of the plant, the explosives detonated. The heavy water electrolysis chambers were destroyed as was almost 120 gallons of heavy water stored on site. The Germans launched an extensive search operation for the commandos but did not find any of them. Some escaped to Sweden, some to Oslo, and a few remained in the general region. Knut Haugland, of Swallow team, eventually was the only member of the two teams who remained in the immediate vicinity.

Although the operation was deemed to be a success, the Germans were able, over several months, to repair some of the damage and restart production of heavy water in April 1943. SOE considered conducting another raid on the plant but dropped the idea as too difficult. In November 1943, the US Army Air Forces were given the mission to conduct a series of bombing raids on the plant. Although only about one in seven of the bombs dropped actually hit the plant, these raids resulted in extensive damage to the plant. Eventually, the Germans decided to halt heavy water operations at the Norsk Hydro plant and to move the supply of heavy water on hand to Germany. Planning and execution of the move was conducted with very tight security. One phase of the movement required railway cars carrying the heavy water to transit Lake Tinnsjo by a ferry, the SF Hydro.

Knut Haugland learned of the plan to move the heavy water and began planning another sabotage operation. He eventually decided that the phase involving the ferry was probably his best opportunity. With the assistance of several members of the local resistance and a crew member on the ferry, Haugland was able to sneak aboard the ferry prior to its departure and place plastic explosives next to the keel, to be detonated by two alarm clock fuses. On 20 February 1944, soon after leaving its dock, the SF Hydro sank into one of the deepest parts of the lake, after the explosives ripped holes in its keel.

The mission of the various teams sent into Norway was completed successfully. The German heavy water development program was finally stopped.

Knut Haugland eventually escaped back to England, after several narrow escapes from the Gestapo. For his actions in the raids, he was awarded the War Cross with Sword, Norway’s highest decoration for gallantry. In 1947, along with another Norwegian (Thor Heyerdahl), who he had met at a training camp in England in 1944, and several others, Haugland took part in the Kon Tiki expedition, crossing part of the Pacific Ocean on a balsa wood raft from east to west. When he died in December 2009, he was the last living member of the Kon Tiki expedition.

* * *

Bibliography of sources consulted:


Gallagher, Thomas; Assault in Norway: Sabotaging the Nazi Nuclear Program; Lyons Press; Guilford, CT; 1975

Haukelid, Hans; Skis Against the Atom; William Kimber; London; 1954

Mears, Ray; The Real Heroes of Telemark: The True Story of the Secret Mission to Stop Hitler’s Atomic Bomb; Hodder & Stoughton; London; 2004

Wiggan, Richard; Operation Freshman: The Rjukan Heavy Water Raid 1942; William Kimber; London; 1986


Grimes, William; “Knut Haugland, Sailor on Kon-Tiki, Dies at 92”; New York Times; 3 January 2010

* * *

© 2023 Michael Dilley.

Published online: 02/02/2014.

Written by Michael F. Dilley. The author retains the copyright to this piece bearing his name. No reproduction, copying, or other forms of retrieval without permission. If you have questions or comments on this article, please contact Michael F. Dilley at:

About the author:
Michael F. Dilley has a B.A. in History from Columbia College in Missouri and is a retired U.S. Army Military Intelligence officer. He served two tours in Viet Nam and six and one-half years in airborne units. In the field of military history, he was written three books (one of them as co-author) and contributed to two anthologies. He has also written many articles and book reviews dealing with special purpose, special mission units.

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