Norwegian heavy water sabotage

The Norwegian heavy water sabotage was a series of actions taken by Norwegian saboteurs during World War II to prevent the Germans from acquiring heavy water which could be used to produce nuclear weapons.

Between 1942 and 1944 a sequence of sabotage actions by the Norwegian resistance movement, as well as Allied bombing, ensured the destruction of the plant and the loss of the heavy water produced. These operations — codenamed "Freshman", "Grouse" and "Gunnerside" — finally managed to knock the plant out of production in early 1943, basically ending the German research.

The raid was later dubbed by the British SOE as the most successful act of sabotage in all of World War II.

Technical background

When Nazi Germany investigated the possibility of building an atomic bomb, a range of possible paths forward seemed possible. Details of how the decision to go down the heavy water route was made are likely to remain somewhat obscure but, although unsuccessful, it was based on what was later demonstrated to be a technically viable aproach:

Plutonium-239 (Pu²³⁹) makes an effective weapons material.
Heavy water has been demonstrated as an effective moderator for Pu²³⁹ production.
Heavy water can be effectively produced by electrolysis.

Approaches to developing a weapon

In nuclear weapon development, the main problem is securing sufficient "weapons grade" material, particular the fissile isotopes of either uranium-235 (U²³⁵) or Pu²³⁹. In order to produce weapons grade uranium, one may elect to extract uranium from natural ore and enrich it. Alternately one can "breed" plutonium in a nuclear reactor using unenriched uranium as a fuel and then chemically separate the Pu²³⁹ produced. Unlike the Allies, which chose to pursue both the enrichment of uranium and production of plutonium in reactors, German scientists elected to focus on plutonium production, as the industrial complex required to make weapons this way was less expensive.

Plutonium production

Although the most common isotope of uranium, uranium-238 (U²³⁸), is useless as fissile material for an atomic bomb, U²³⁸ can be used to produce Pu²³⁹. The fission of U²³⁵ produces neutrons, some of which will be absorbed by U²³⁸ creating U²³⁹. After a few days the U²³⁹ will decay, turning into weapons-usable Pu²³⁹. The Germans did not examine ultrapure graphite, but instead settled on the heavy-water-based reactor design The heavy water concept was perfectly viable—one needs only consider the heavy water moderated production reactors at Savannah River Site’s R-Reactor, P-Reactor, L-Reactor, K-Reactor, & C-Reactor or Mayak’s production reactors to see compelling proof that heavy water is fully effective for plutonium production if available in sufficient quantities. . A heavy water moderated nuclear reactor could be used to do nuclear fission research, and, ultimately, to breed plutonium from which a bomb could be constructed.

Heavy water production

Heavy-water production is a byproduct of ammonia fertilizer production. Hydrogen is produced by electrolysis of water. The Haber Process is then used, reacting the hydrogen with nitrogen from air to produce ammonia. At the time, Europe's major supply of ammonia came from the Norwegian Vemork hydroelectric plant, run by Norsk Hydro, near Rjukan in the Telemark region.

The technology is straightforward. Heavy water (D₂O) is separated from regular water by electrolysis because the difference in mass between the two hydrogen isotopes translates into a slight difference in the speed at which the reaction proceeds. To produce pure heavy water by electrolysis requires a large cascade of electrolysis chambers, and consumes large amounts of power. Since the production of hydrogen relied on electrolosis at Vemork, heavy water was a routine byproduct.

Hans Suess was a German advisor to the production of heavy water. Suess had assessed the Rjukan plant as being incapable of producing militarily useful quantities of heavy water in less than five years at its then current capacity.

Operations Freshman and Grouse

Destruction of the plant was mounted by the Combined Operations command in November 1942. The plan consisted of two operations: the first would drop a number of Norwegian locals into the area as an advance force, and once in place a party of British engineers would be landed by glider to attack the plant itself.

On 19 October 1942, a four man team of Special Operations Executive (SOE) trained Norwegian commandos were parachuted into Norway. From their drop point in the wilderness they had to ski a long distance to the plant, so considerable time was given to complete this part of the mission, known as Operation Grouse. This plan, unlike those which did not succeed before, included the team studying and memorising blueprints.

Once the Norwegian Grouse team managed to make contact with the British, the British were suspicious, as they had not heard from the team for a long time, many months, as they went off course many times, and were dropped at the wrong place. The British also considered the possibility of Germans contacting them. The secret question took form of: "What did you see in the early morning of (a day)?" The Grouse team replied: "Three pink elephants." The British were ecstatic at the success of the team, and went on with their next phase of operations.

On 19 November 1942, Operation Freshman followed with the gliderborne landing onto the frozen lake Møsvatn near the plant. The two Airspeed Horsa gliders, towed by Handley Page Halifax bombers, each carried two glider pilots and fifteen Royal Engineers of the 9th Field Company, 1st British Airborne Division took off from RAF Skitten near Wick in Caithness. The towing of gliders had always been a hazardous profession, however the circumstances were made worse by the long flying distance to Norway and poor weather conditions which heavily restricted visibility. One of the Halifax tugs crashed into a mountain, killing all seven aboard, however its glider was able to cast-off and crashed nearby, resulting in several deaths and injuries to the occupants. The other Halifax successfully delivered its charge to the area of the landing zone, but although the conditions had substantially improved it was quite impossible to locate the actual zone itself due to the failure of the link between the Eureka (ground) and Rebecca (aircraft) beacons, which was to pinpoint the zone. After much endeavour and with fuel running low, the pilot made the decision to abort the operation and return to base, however shortly afterwards the tug and glider combination encountered heavy cloud and in the resulting turbulence the tow rope broke away. The glider made a crash-landing, not far from where the other glider had come down, similarly inflicting several deaths and injuries. The Norwegians were unable to reach the crash sites in time, and the survivors quickly came into the hands of the Gestapo, who tortured them, including the badly injured, during interrogation and later had them executed under Hitler's Commando Order.

The Norwegian Grouse team thereafter had a long arduous wait in their mountain hideaway, subsisting virtually on moss and lichen during the winter until a reindeer was eventually found and shot just before Christmas.

A 1948 Norwegian movie based on this raid, called Kampen om tungtvannet, features performances by at least four of the original participants in the raid. ^*

Operation Gunnerside

British command was aware of the "success" of the Grouse team, and decided to build another operation in concert with them. By this time the original Grouse team were being referred to as Swallow. In February 1943, in Operation Gunnerside, an additional six Norwegian commandos were dropped into Norway by a Halifax bomber of 138 Squadron from RAF Tempsford. They too were successful in landing, and found the Swallow team after a few days of searching. The combined team then made final preparations for their assault on the night of 27 February. (Supplies required by the commandos were dropped with them in special CLE containers. One of these, buried in the snow by a Norwegian patriot to hide it from the Germans, was recovered by him and handed over to an officer of the Army Air Corps, who were exercising in the area in August 1976. The container was brought back to England and is now on display at the Airborne Museum at Aldershot.)

Following the Freshman attempt, mines, floodlights and additional guards were set around the plant. Whilst the mines and lights remained in place, security of the actual plant had slacked somewhat over the winter months. However, the single 75 metre bridge spanning the deep ravine which led to the plant, 200 metres above the River Maan, was well guarded.

The force elected to descend into the ravine, ford the icy river and climb the steep hill on the far side. The winter river level was very low and on the far side, where the ground leveled, they followed a single railway track straight into the plant without encountering any guards. Even before Grouse landed in Norway, SOE had a Norwegian agent within the plant who supplied detailed plans and schedule information. The demolition party used this information to enter the main basement by a cable tunnel and through a window.

The saboteurs then placed explosive charges on the heavy water electrolysis chambers, and attached a fuse allowing sufficient time for their escape. Other than keeping the night watchman quiet, no one interfered with their mission or immediate escape following what they described as a "dull thud". A British machine gun was purposely left to indicate this was a British raid and not local resistance, to try to prevent reprisals. The explosive charges detonated, destroying the electrolysis chambers and releasing the stocks of heavy water.

All ten made good their escape whereafter six skied 400 kilometres to Sweden while four remained in Norway for further work with the resistance. The plant was restored by April and SOE concluded a repeat raid would be extremely hard as German security was thereafter very considerable. In November the plant was attacked by a massed daylight bombing raid of 143 B-17 bombers dropping 711 bombs, of which at least 600 missed the plant, the damage, however, was quite extensive; the reason for the original ground assault a year earlier was that the available alternative of night bombing was considered unrealistic at that time.

Aftermath

While this attack did little damage to the plant, it did stop production for a short period. Almost as soon as production re-started, the USAAF started a series of raids on it. The Germans were convinced that this would eventually result in some "hits", and they decided to abandon the plant and move remaining stocks and critical components to Germany in 1944.

Knut Haukelid discovered their plan and decided to sabotage a ferry carrying the heavy water across lake Tinnsjø. He recognised a crew member and talked to him, taking this advantage to slip into the bottom of the ship and plant the bomb, after which he escaped. Eight and half kilograms of plastic explosive with two alarm-clock fuses were fixed to the keel of the ferry, Hydro, which was to carry the railway tankers of the water. On 20 February 1944, just after midnight, the ferry and its cargo sank shortly after sailing when in deep water, finally capping the original mission's objective and halting Germany's development programme. A number of Norwegian civilians were killed as the ferry sank. Witnesses reporting seeing barrels floating after the sinking, leading to speculation that they did not really contain heavy water. But an examination of records after the war showed that some barrels were only half full, and therefore would have floated. A few of these may have been salvaged and transported to Germany. Around 2005, an expedition retrieved a barrel (numbered "26") from the bottom of the lake. Its concentration of heavy water matched the records, and confirmed that the shipment was not a decoy.

Unknown to the saboteurs, a “Plan B” had been set-up by the SOE, who arranged a second team to attack the shipment at Herøya should the first attempt fail. The disassembled factory was later found in southern Germany during the closing stages of the war by members of Operation Alsos nuclear seizure force.

With the benefit of hindsight, the consensus opinion on the German wartime nuclear program is that it was a long way from producing a bomb, even without the sabotage. Nevertheless, the feats of the Norwegian saboteurs have made them national heroes.

SOE Norwegian agents involved

The first agent inside the plant Einar Skinnarland

The Grouse/Swallow Team Jens Anton Poulsson
Arne Kjelstrup
Knut Haugland
Claus Helberg

The Gunnerside Team Joachim Rønneberg
Knut Haukelid
Fredrik Kayser
Kasper Idland
Hans Storhaug
Birger Strømsheim
(Leif Tronstad) (planner, in the United Kingdom)

The Lake Tinnsjø Team “Bonzo” alias Knut Haukelid
Rolf Sørlie (local resistance)
Einar Skinnarland (base wireless operator)
Gunnar Syverstad (plant lab assistant)
Kjell Nielsen (plant transport manager)
(“Larsen”) (senior plant engineer)
(NN) (car procurer and driver)

Books, films and radio programme

A French/Norwegian black and white docu-film from 1948 titled La Bataille de l'eau lourde / Kampen om tungtvannet (trans. "The Fight Over the Heavy Water"), featured some of the original saboteurs.
Some of these exploits were used as the basis for the US 1965 war movie The Heroes of Telemark starring Kirk Douglas whose character, Dr. Rolf Pedersen, was supposed to be Joachim Rønneberg. Rønneberg himself has stated, "The Fight over the Heavy Water was an honest attempt to describe history. The Heroes of Telemark, on the other hand, had little to do with reality."
The book The Real Heroes of Telemark: The True Story of the Secret Mission to Stop Hitler's Atomic Bomb by Ray Mears, published by Hodder & Stoughton 2003 (ISBN 0-340-83016-6) describes the events from the perspective of the unique survival skills of the Norwegian commandos. It accompanied a BBC television documentary series, The Real Heroes of Telemark, which sticks more to the facts than the film it is named after. It also describes the survival aspects of the attack - how to survive for months in a mountain cabin. The name is an obvious pun on above film and its inaccuracy.
The book Skis Against the Atom (ISBN 0-942323-07-6) is a full first-hand account by Knut Haukelid, one of the raiders who stayed behind.
The book Assault In Norway: Sabotaging the Nazi Nuclear Program by Thomas Gallagher, published by Harcourt Brace Jovanovich, 1975 (ISBN 0151095825) / The Lyons Press, 2002 (ISBN 1585747505) focuses on the part played by the Norwegian commandos.
The book Operation Freshman: The Rjukan Heavy Water Raid, 1942 by Richard Wiggan, published by W. Kimber, 1986 (ISBN 071830571X) focuses on the ill-fated Operation Freshman.
The book "Blood and Water: Sabotaging Hitler's Bomb" by Dan Kurzman, published by Henry Holt & Company, 1997 (ISBN 0805032061) documents all operations against the Vemork plant.
The book E=MC2: A Biography of the World's Most Famous Equation (ISBN 0-330-39165-8) has a rather detailed section on the raid.
The book Between Silk and Cyanide by Leo Marks has a chapter about the raid, from the viewpoint of an SOE cryptographer who helped organize the communications between the SOE and the saboteurs.
The 2005 public television documentary Hitler's Sunken Secret
BBC Radio 4 programme Telemark Heroes, Julian Pettifer talked to survivors of Operation Gunnerside, Listen Again

References and notes

External links

Military history of Norway during World War II

Bataille de l'eau lourde | Operatie Freshman | Vemork-aksjonen | Tungtvannsaksjonen

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