Operation Gunnerside: The Real Heroes of Telemark
The Battle for Heavy Water (Part 2)
In Part 1 of this two-part essay, I explained that by March 1940 physicists on both sides of the war had discovered two approaches to making an atomic bomb. In the first, quantities of the fissionable isotope uranium-235 (U-235) would need to be separated from the much more common isotope U-238 sufficient to assemble a so-called super-critical mass. The ‘Little Boy’ bomb dropped on Hiroshima contained about 56 kilos of uranium enriched to about 90% U-235. The second relied on a fissionable isotope of plutonium, produced in a nuclear reactor. The ‘Fat Man’ bomb dropped on Nagasaki contained a little over 6 kilos of plutonium.
Separating sufficient U-235 was judged to be incredibly difficult, though not impossible. Attention therefore became focused on building a nuclear reactor principally to breed plutonium. A working reactor requires a ‘moderator’ to slow down the neutrons released by fission reactions, so that they can fission more uranium nuclei in a self-sustaining chain reaction. The world’s first nuclear reactor was assembled on a squash court at the University of Chicago on 2 December 1942. It consisted of a ‘pile’ of ultra-pure graphite bricks (the moderator), about 5 tonnes of uranium metal, and 40 tonnes of uranium oxide. Two and a half years previously, the German Uranverein (Uranium Club – the Nazi bomb project) had eschewed graphite as a moderator in favour of ‘heavy’ water, in which the two hydrogen atoms in H2O are replaced by heavier deuterium isotopes, D2O. They had likely been misled by boron impurities in the sample of graphite they had tested.
The German physicists could acquire quantities of uranium relatively easily, but the only source of heavy water in Europe was a fertilizer plant operated by Norsk Hydro, perched high in the fjords at Vemork near the town of Rjukan in the remote Telemark district of southeastern Norway, about 150 miles west of Oslo. As Part 1 relates, the plant’s entire stock of 185 kilos of heavy water had been gifted to the French government and smuggled to Britain following the fall of France in June 1940. But the Nazi occupation of Norway that same month suggested there would be nothing to stop the Uranverein physicists getting all the heavy water they needed.
The little intelligence that could be gathered on the progress of various Nazi atomic research projects all suggested that the Allies should hasten their own efforts, and do whatever they could to frustrate the German physicists.
A Certain Passive Resistance
Jomar Brun was head of Hydrogen Research at Norsk Hydro when in 1933 he realised the potential for large-scale production of heavy water at the Vemork plant, whose primary function was to produce ammonia. With inorganic chemist Leif Tronstad from the Norwegian Institute of Technology in Trondheim, he drew up plans for a heavy water production facility involving hundreds of electrolysis, combustion, and condensation cells. It was an incredibly speculative proposal, but Norsk Hydro had given the go-ahead and the facility met its first order in August 1934. Tronstad and Brun published important results on the physical properties of heavy water in the British journal Nature in 1935.
Uranverein physicists visited Brun at the plant in May 1941, and discussed their requirements and proposals to expand production capacity using a new catalytic process. But they were evasive about what they wanted the heavy water for. Efforts by Britain’s Secret Intelligence Service (SIS, also known colloquially as MI6) to find out what the German physicists were up to were greeted with puzzlement by Tronstad, who was by now collaborating with the Norwegian resistance. Tronstad was not a nuclear physicist and was likely unaware of the significance of heavy water. He didn’t have much time to ponder. The Gestapo uncovered and shut down the operation in which he was involved in September 1941, and he was obliged to escape with his family to Britain the following month.
In Britain, Tronstad met with Lieutenant-Commander Eric Welsh, a veteran SIS operative. Welsh spoke fluent Norwegian and had worked for many years in Bergen, where his expertise in industrial paints had been put to good use in the design of special corrosion-resistant floor tiles used at the Vemork plant. Welsh knew Brun, and was broadly familiar with the layout of the plant. He briefed Tronstad about the significance of heavy water and Tronstad told the SIS all he knew.
On Tronstad’s recommendation, Brun began to sabotage the heavy water facility by adding castor oil to the electrolyte, halting production for several hours, sometimes days. The effects were so severe at times that Brun had to moderate his efforts to avoid suspicion. He did not realise it at the time, but he was not the only one at the plant involved in this kind of sabotage. Others were adding cod liver oil to the electrolyte.
In April 1942 the whole plant was shut down and no heavy water was produced at all. In May the number of concentration cells used at the plant was doubled, but the additional cells did not begin producing until mid-June. The lack of progress was put down to a ‘certain passive resistance’ by the plant’s Norwegian operators and engineers.
But the Uranverein was still able to make progress. At his laboratory at Leipzig University, Werner Heisenberg had assembled L-IV, an experimental reactor consisting of powdered uranium metal and about 140 kilos of heavy water, arranged in a spherical configuration with two concentric layers of uranium separated by the moderator. There could be no mistaking the evidence for neutron multiplication, which Heisenberg and his assistant estimated at 13%. ‘So we have at last succeeded in building a pile configuration that generates more neutrons than it absorbs’. They estimated that a pile consisting of ten tons of uranium metal and five tons of heavy water would produce a self-sustaining nuclear chain reaction.
Grouse and Freshman
The dependence on heavy water from the Vemork plant represented a significant vulnerability for the German atomic programme. Sabotage had certainly limited production – of the five tons that Heisenberg had estimated to be required, by June 1942 less than a ton of heavy water had actually been delivered. However, it was obvious that this kind of sabotage could not be sustained indefinitely. Better to restrict German access to heavy water altogether by taking the plant out of commission.
Winston Churchill had been briefed and, shortly after returning from a strategy meeting with US President Franklin Roosevelt in June 1942, the Vemork plant was identified as a top priority target. There were few options. Tronstad argued strenuously against a bombing raid, which he feared would be too indiscriminate. Given the remoteness of the plant, any commandos landed in the region would have great difficulty getting out again, turning a sabotage operation into a potential suicide mission. And any actions taken by locals risked German reprisals against the local population.
Discussions dragged on through August and September. In the meantime, the ranks of the Norwegian Section of the Special Operations Executive (SOE), established by Churchill in July 1940 to facilitate espionage and sabotage behind enemy lines, were scoured for potential candidates for the raid. Ten men were identified, and the SOE began putting together plans for landing a small advance party onto Norway’s notoriously inhospitable Hardangarvidda – the Hardanger Plateau: 3,500 square miles of virtually uninhabited, frozen wilderness about 3,000 feet above sea level, on the edge of which the Vemork plant was perched.
One of those selected was Knut Haukelid, who subsequently gave a detailed account of the training that he and his comrades received in various SOE Special Training Schools. An accident with a loaded pistol during a field exercise ruled him out of the advance party, which was given the codename Grouse, led by Second Lieutenant Jens Anton Poulsson. The Grouse party included Claus Helberg, Knut Haugland, and Arne Kjelstrup. Poulsson, Helberg, and Kjelstrup were all natives of Rjukan (Poulsson and Helberg had been school classmates, Kjelstrup had been born in Rjukan but had lived most of his life in Oslo). All four were hardened ‘hillmen’, intimately familiar with the survival challenges of the Hardanger wilderness.
The Grouse party was to reconnoitre the area and identify a suitable landing site for a further party of glider-borne commandos, comprised of Royal Engineers of the First Airborne Division, who would carry out the raid. After destroying the heavy water plant, the commandos were expected to make their way on foot to the Swedish border, about 400 kilometres away.
Tronstad and Colonel John ‘Jack’ Wilson, commander of the SOE’s Norwegian Section, argued that the plan was ill-conceived and susceptible to failure. Norway was unsuitable for a glider operation, over a towing distance longer than had ever been attempted, even in daylight. Success would demand very favourable weather conditions, something that could not be guaranteed. They were overruled, and Tronstad sent word to Brun that he and his family should leave for Britain without delay.
After a couple of aborted attempts during September, the Grouse party parachuted onto the Hardanger Plateau on 18 October 1942, 30 miles from their designated drop zone. Although the weather had been fine at the time of the drop, the Grouse party was subsequently hit by several storms and took fifteen days to trek to their base of operations close to the Møsvatn (Mos Lake) dam. ‘In good weather, it would have taken us a couple of days,’ Poulsson later said, ‘but because the snow was wet, the ground wasn’t frozen, the streams and lakes were open [ice-free], it took us one hell of a long time with all that equipment’. Television survivalist Ray Mears re-created this trek for a three-part documentary series first broadcast by the BBC in 2003.
The group made contact with brothers Einar and Torstein Skinnarland and radioed their arrival back to the SOE on 9 November. Three days later the advance party signalled that they had found a suitable landing site, five kilometres to the south-west of the Møsvatn dam. The planning for Operation Freshman was finalised at SOE headquarters in Baker Street a few days later, and on 18 November Churchill gave the operation a green light.
But the operation went wrong virtually as soon as it began. The target was judged sufficiently important to warrant a doubling of the personnel for the mission, making a total of 34 men, all volunteers. Both gliders and one of the Halifax bombers used to tow them crashed. Those who did not die in the crashes were rounded up and executed by the Gestapo. Some were tortured first. Hitler had been infuriated by the success of British sabotage operations, and had just a few weeks before issued a new order. No quarter was to be granted to saboteurs, on principle, even if they were in uniform at the time of their capture.
From maps and other documentation salvaged from the crashed gliders and, no doubt, from the Gestapo’s brutal interrogation of the crash survivors, the Germans learned all they needed to know about the target of Operation Freshman. They fortified their positions in Rjukan and laid a minefield around the plant.
Now in great jeopardy, the four-man Grouse party vanished into the depths of the Hardanger wilderness.
Swallow and Gunnerside
Torstein Skinnarland was arrested in one of many German sweeps of the local population following the failed commando raid. He was sent with his brother Olav to Grini concentration camp, located in a suburb of Oslo. Einar was forewarned of the raid and managed to escape onto the Hardanger Plateau, where he joined Poulsson and the other members of the advance party, now renamed Swallow.
Back in London, the SOE was faced with a very difficult decision. Forty-one personnel had perished in the failed Freshman operation. Yet the high concentration cells at Vemork remained intact and continued to supply the heavy water required by the German atomic project. Nothing had changed: the destruction of the heavy water plant remained a top priority, although this was a task now made doubly difficult.
It was obvious that an operation like Freshman could not be repeated. The challenge was passed back to the SOE, and an alternative plan was devised. This time, the SOE had the advantage of Brun’s intimate knowledge of the plant. Both Tronstad and Brun felt strongly that a small sabotage party could succeed where the larger-scale commando raid had failed.
A team of six Norwegians was drawn from the ranks of the Norwegian Independent Company, led by 22-year-old Joachim Rønneberg, regarded as one of the best of the commandos from among those who had graduated from the SOE’s Special Training Schools. Rønneberg selected Haukelid, who had by now recovered from the wound he had picked up in training, Kasper Idland, Fredrik Kayser, Birger Strømsheim, and Hans Storhaug. All were accomplished skiers and outdoorsmen.
Unusually, all six were fully briefed by Tronstad about the fate of Operation Freshman, and Hitler’s new commando directive. Tronstad and Wilson ‘had thought it best to explain the whole situation to us,’ Haukelid later wrote, ‘We must be prepared to receive no better treatment than the British soldiers if we were taken prisoner’.
The new raid was codenamed Operation Gunnerside. This time the planning was detailed and meticulous. Under Tronstad and Brun’s direction, a replica of the heavy water plant was constructed at the SOE’s Special Training School (STS-17) in Hatfield, Hertfordshire. The sabotage team practiced laying charges in precisely the right place on each high concentration cell to cause maximum damage. ‘None of us had been to the plant in our lives but by the time we left Britain we knew the layout of it as well as anyone,’ said Rønneberg.
Each member of the team was issued with suicide pills, small quantities of cyanide encased in rubber that, if bitten through, would ensure death in three seconds. On their last day at STS-17, Tronstad explained how their mission would live on in Norway’s history in a hundred years’ time.
From Hatfield they headed north to STS-61, a large eighteenth-century country house near Godmanchester in Cambridgeshire, known as ‘Farm Hall’. It belonged to the SOE but was used as a staging-post for SIS agents about to depart for occupied territories, and as a debriefing or interrogation centre for agents or captives coming into Britain. Welsh had had Farm Hall wired throughout with concealed listening devices in all the bedrooms and reception rooms. A listening post was installed in a service wing, behind doors secured by special locks.
Whilst it was pleasant, the team’s extended stay at Farm Hall frayed their nerves. In December 1942 Operation Gunnerside was delayed by bad weather. Rønneberg insisted on a return to more arduous training in Scotland. The mission was delayed again on 23 January 1943, when the RAF pilot and navigator failed to find the designated drop zone and, running low on fuel, turned around and headed back to base.
On the Hardanger Plateau, the Swallow team was experiencing the worst weather in living memory, the temperature barely rising above -30oC. Though still in good spirits, their food rations were now very meagre and their health was deteriorating. When the Gunnerside team got airborne again on 16 February, the advance party had been holding out in Europe’s most inhospitable wilderness for nearly four freezing months. They were in bad shape.
The advance party had been advised by wireless that the Gunnerside party had landed, but a severe storm had since descended and after several days without contact they began to fear the worst. A week later, the Gunnerside team finally made contact with two of the advance party, Helberg and Kjelstrup, who had been sent by Poulsson to search for them. Four months on the Hardanger Plateau had taken its toll. Helberg and Kjelstrup looked like tramps, their clothes filthy and covered in reindeer blood, bearded, malnourished, their emaciated faces a sickly yellow.
Back-slapping and hearty congratulations were followed by a veritable feast of reindeer and fresh rations. After a couple of days’ recuperation, the Norwegians were ready to mount their attack. Helberg was dispatched to Rjukan to source information on the Vemork defences from a contact in the town, an engineer at the plant called Rolf Sørlie. The team then set to work to figure out how they were going to carry out their task.
There were about thirty German troops based at the plant itself, with many more garrisoned in Rjukan. The plant could only be reached from the road by a narrow suspension bridge, about 75 feet long. The bridge spanned the deep ravine which now separated the saboteurs from their target. The bridge was closely guarded. Gaining access to the plant without being detected and without an exchange of fire appeared impossible.
But what had been considered impossible by the German defenders was considered quite feasible by the Norwegian attackers. Helberg discovered that it was indeed possible to descend into the ravine, cross the frozen river Måna at the bottom and ascend the other side, where the saboteurs could access a railway line cut into the mountainside. The railway line, which ran from Vemork to Rjukan, was used only occasionally to transport heavy machinery to the plant. It was not guarded. They had found a way in.
Finding a way out was more problematic. The explosion would undoubtedly alert the German troops, and if they chose to retreat via the ravine they risked becoming trapped. Rønneberg and Poulsson favoured fighting their way out across the bridge, but the others were not convinced. Democracy prevailed, and a retreat via the ravine was agreed.
The party split into two teams. Rønneberg led the sabotage team which included Idland, Kayser, and Strømsheim. Haukelid led the covering team, comprised of Poulsson, Helberg, Kjelstrup, and Storhaug. Haugland and Skinnarland were to remain in wireless contact with the SOE and report the results of the operation.
They set out at eight pm on Sunday, 28 February 1943. They all wore British uniforms and carried British papers so that their action would be seen as a military operation, hopefully reducing the risk of reprisals against the local population. Although it was a steep climb, they crossed the ravine without incident and managed to get to the railway line. They walked along the railway line, a strong southwesterly wind covering any noise they made. They reached a small building about 500 yards from the plant at about 11:30, and waited for the change of sentry on the suspension bridge which was due at midnight.
The group separated at 00:30. The sabotage team cut through the flimsy chain on the fence around the plant and headed for the heavy water concentration cells in the basement. They split into two pairs as they tried to find a way in. Rønneberg and Kayser eventually gained access via a narrow cable shaft, surprising the nightwatchman inside. Kayser covered the nightwatchman with his gun, as Rønneberg started to place charges.
He was about half way through when Strømsheim crashed in through a window. He and Idland had tried to get in through the door on the ground floor, but had found it locked. Unable to find any other way in, they had decided to risk a noisy break-in. Kayser instinctively swung his gun from the nightwatchman to the window. ‘I almost killed him,’ Kayser said later, ‘If there had been a bullet in the chamber of my gun, I probably would have. I recognised him just in time’.
Idland kept watch outside the broken window as Rønneberg and Strømsheim placed the last of the charges. They had set the fuses when they were interrupted by a plant foreman. Rønneberg lit the fuses and Kayser suggested to their two captives that they head upstairs as quickly as possible. By his reckoning, they should be able to get to the second floor before the explosion. The saboteurs left by a cellar door, and were no more than twenty metres from the building when they heard a muffled explosion.
‘The explosion itself was not very loud,’ Poulsson later recalled, ‘It sounded like two or three cars crashing in Piccadilly Circus’. Inside the building it was a different matter, with one plant engineer who had been up on the third floor remarking: ‘The explosion was tremendous, the power of it reverberated throughout the entire building’.
The sabotage party took cover as Haukelid and the covering team prepared for the appearance of German troops from the nearby barracks. But outside the explosion had not been loud, and small explosions from the plant’s combustion equipment (called ‘cannons’ because of their shape) were not unusual. A single guard appeared, flashed a torchlight inches above Haukelid’s head, and went back inside.
The covering and sabotage parties reunited. They began their retreat back along the railway line, and then back down the ravine. They were crossing the now rapidly thawing river at the bottom when they heard the first sounds of sirens. Rønneberg had feared they would be trapped in the ravine, picked out by searchlights with no means of escape. But the Germans were busy searching the plant itself, convinced the saboteurs were still somewhere on the premises. They knew nobody had passed the sentries on the bridge, and as far as they were concerned that was the only way out.
The raid had been a success, and now the party’s main concern was for their own safety. They scrambled up the other side of the ravine. The road from Rjukan was now busy with traffic, including trucks carrying more German troops. Across the ravine they could see flashlights darting through the night as Germans traced their retreat along the railway line. They didn’t have much time.
They followed the power line towards Rjukan, and then climbed up a road that zig-zagged beneath a cableway. The cableway had been built before the war to allow the citizens of Rjukan an opportunity to escape the gloom of winter during its four long months of perpetual darkness. It was now discontinued for public use. The road led up to the top of the cableway at the edge of the Hardanger Plateau.
There had been no exchange of fire. Aside from a couple of Norwegian workers at the plant, nobody had seen the raiders enter or leave. Between four and five months’ production of heavy water – about 500 kilos – washed uselessly over the basement floor.
General Wilhelm Rediess, head of the Gestapo in Norway, decided that this was the action of British Intelligence and the Norwegian resistance, and threatened to execute ten of Rjukan’s leading citizens in reprisal. Arriving on the scene shortly afterwards, Generaloberst Nikolaus von Falkenhorst, commander-in-chief of the German forces in Norway, decided instead that this had been a military operation, carried out by uniformed British soldiers. He called it ‘the finest coup I have seen in this war,’ and ordered that the Rjukan citizens be released. Falkenhorst was tried for war crimes in July-August 1945. He was found guilty of seven (of nine) charges, including a charge relating to the murder of nine commandos of Operation Freshman. His initial death sentence was commuted to twenty years’ imprisonment. He was released on the grounds of ill-health in 1953, and died in 1968. Rediess committed suicide in May 1945.
Falkenhorst’s admiration spilled over into the mainstream media. A report on Swedish radio on 1 March 1943 claimed that the sabotage of the heavy water facility at Rjukan was intended to disrupt production of ‘high quality explosives’. A garbled account appeared in the Daily Mail on 2 March, submitted by the Mail’s correspondent in Stockholm. This account contained no reference to heavy water. A further report in the Svenska Dagbladet linked the raid with a ‘secret weapon’ based on heavy water. The Times reported on the raid on 4 April. On the same day the story made its way into the New York Times, which made a muddled connection between heavy water and atomic energy. To General Leslie Groves, appointed as the military head of the Manhattan project and an Anglophobe, these press reports were examples of lax security.
Escape from Norway
After successfully completing their sabotage mission, the Norwegian commandos of Swallow and Gunnerside went separate ways, as Falkenhorst and Reichskommisar Josef Terboven ordered a massive search. Rønneberg led Idland, Kayser, Strømsheim, and Storhaug north towards the Swedish border. They arrived on Swedish soil fifteen days later, exhausted from a 400-kilometre trek that had not been without incident but which had been relatively straightforward.
Poulsson and Helberg headed for Oslo, intending to lay low for a while before making contact with the Norwegian resistance. From Oslo Poulsson escaped into Sweden before returning to Britain for a short while. Helberg, who had done time in a Swedish prison and was therefore known to the authorities, planned to head back to the Hardanger Plateau when the dust had settled. Acting on incorrect advice, on 25 March 1943 he arrived back in an area that was still crawling with German troops. Realising he had been spotted, he set off on skis as three German soldiers gave chase. Two gave up after an hour. After two hours, Helberg turned and faced his lone pursuer. The German emptied his Luger, missing with every shot. Helberg gave chase, bringing the German down with a single shot from his Colt .32.
More adventures were to follow. In darkness, Helberg fell over a precipice and broke his left shoulder. He reached his destination, a house he knew in the village of Rauland, only to find it full of German troops. He bluffed his way through the next two nights, drinking and playing cards with the troops, and even managed to get medical attention for his shoulder. He moved to a hotel in Dalen, where he was unfortunate to get caught up in an altercation between Terboven, who was staying in the next room, and a young, attractive Norwegian woman who had spurned Terboven’s amorous advances. Helberg was rounded up with the other Norwegians in the hotel on the orders of a now incensed Terboven, and was told they were all to be sent to Grini concentration camp. Helberg jumped from the bus on the way to Oslo, avoiding grenades and pistol shots. He eventually managed to get to Sweden, avoided imprisonment, and boarded a plane bound for Britain on 2 June.
Haugland and Skinnarland relocated their makeshift wireless operation to a location high in the mountains. They took cover under the snow and watched the German troops make a mess of the search on the Hardanger Plateau. Haugland completed Skinnarland’s wireless training before joining his brother, who he was surprised to find leading the resistance in Oslo. He provided the resistance with further SOE-style training in the use of explosives.
Haukelid and Kjelstrup headed west on the Hardanger Plateau, where they stayed for much of the summer of 1943. Kjelstrup’s health began to suffer, and he returned to Britain to recuperate.
Bombing Raid
Gunnerside had been successful, but Tronstad was greatly concerned by news that the Germans had managed to get the heavy water plant up and running again unexpectedly quickly. Skinnarland, reporting from a makeshift radio station on the Hardanger Plateau, had estimated that the plant would return to full production by mid-August. Tronstad was also concerned that a new ‘combustion’ method of separation could, if adopted at Vemork, lead to production at a much accelerated rate. The job that the SOE had set out to do was clearly not yet done. Production was again delayed by small, limited acts of sabotage, but another way had to be found to take the plant more fully out of commission.
Tronstad tried to devise further large-scale sabotage operations, but the defences at the plant had been greatly strengthened. Vemork was now surrounded by barbed wire fences and minefields, and the garrisons at Vemork and Rjukan had been substantially increased. A further commando raid seemed out the question. The only alternative appeared to be a bombing raid. Tronstad and Wilson remained firmly opposed.
But Groves was insistent. He did not trust the British. He had not been informed of the failed Freshman raid until after it had ended in disaster. He had learned of the Gunnerside raid through a casual remark made by a British contact in January. He now urged the British to agree appropriate action.
In fact, an SOE memorandum of 20 August 1943 had acknowledged that a bombing raid was the only viable option and should be given active consideration. The memo also advised that the Norwegian High Command and Norwegian government-in-exile should not be informed of such plans. By mid-October, a full-scale ground assault or a further sabotage raid had been firmly ruled out.
Groves was not prepared to take the risk that the German programme might be successful, if not in producing a bomb, then perhaps some sort of radiation weapon. He ordered a bombing raid, his first combat decision after 25 years in uniform.
A force of about three hundred B-17 Flying Fortresses and B-24 Liberators of the American Eighth Air Force took off from airfields in East Anglia just before dawn on 16 November 1943, in poor weather conditions. Part of this force headed for targets near Stavanger and Oslo to divert German fighters away from the main force heading for Vemork. The raid had been carefully timed to coincide with the lunch break, between 11:30 am and noon, when most of the plant’s workforce would be off-site.
No fighters were encountered and the bombers arrived at the Norwegian coastline twenty minutes too early. The commander, Major John M. Bennett, ordered the fleet to circle back out over the sea and return for the bombing run at the right time. The decision traded civilian casualties for military: as the bombers returned to the coastline one was shot down by anti-aircraft fire from the now fully alert coastal defences. The crew of a second parachuted into the sea as their plane spun out of the air with an engine on fire.
From their vantage point on the Hardanger Plateau, Haukelid and Skinnarland both watched as: ‘Scores of American bombers were flying across Norway in broad daylight as if no German anti-aircraft defences existed. They began to circle over us and then proceed in an easterly direction, towards Rjukan’.
In the first wave of the attack about 145 bombers dropped more than seven hundred 1,000-pound high explosive bombs on the Vemork plant. Fifteen minutes later a second wave of about forty bombers dropped 295 500-pound bombs on Rjukan. But in World War II so-called precision bombing was far from precise. The bombs fell everywhere. The plant itself received just two hits, damaging the top floors but leaving the electrolysis cells, in the basement, completely unharmed. The plant’s power station was hit, as was the nitrate plant in Rjukan. Twenty-two civilians were killed.
The Norwegians were absolutely furious, and lodged formal protests with both the British and American governments. They argued that the attack ‘seems out of all proportion to the objective sought’. Tronstad pointed out that he had given all the reasons why a bombing raid would not be successful four months before.
And yet the raid was successful, if not quite in the manner intended. The Germans had finally got the message that the Vemork plant was not secure; that the Allies would continue to attack it until it was utterly destroyed. Production of heavy water at Vemork was stopped and plans were laid to build a plant in Germany.
Sinking the Hydro
The last of the heavy water was to be transported to Germany by sea, under armed guard. The SOE was alerted early in January 1944, and Haukelid was asked to look at ways to prevent the heavy water from leaving Rjukan.
A one-man attack on the plant itself was impossible, so Haukelid turned his attention to the transport arrangements. The drums containing the heavy water, labelled ‘Potash-lye’, were to be moved by train from Vemork to the Hydro, a ferry that would cross Lake Tinnsjø, and thence by rail to a port and a waiting ship to Germany. The ferry itself was the least guarded and offered the prospect of minimising civilian casualties. On 9 February he sent a telegram back to London suggesting sabotage of the ferry. Although the saboteurs went on to express their misgivings that the operation was not worth the risk of reprisals that would certainly follow, the response from London was clear. The heavy water had to be destroyed.
Haukelid, Skinnarland, and Sørlie planned to sink the ferry at the deepest point in the lake, sending the drums of heavy water to the bottom. The battle for heavy water was about to claim its last casualties.
Armed with sten guns, pistols, and grenades, Haukelid and Sørlie smuggled themselves aboard the ferry in the early morning of Sunday, 20 February. On the inside of the hull they placed nineteen pounds of plastic explosive, high-speed fuses, detonators and timers hastily assembled from old alarm clocks. They set the clocks for 10:45 am, before making their escape.
The Hydro sailed on time at 10:00 am carrying 53 passengers, crew, and German guards, and 39 drums containing over 3,600 gallons of heavy water. The explosion ripped a hole eleven feet square out of the side of the 493-ton ferry. It sank within three minutes. Twenty-six drowned, including fourteen civilians, among them a couple and their three-year old daughter. The other 27 managed to jump from the ferry as it sank, and were rescued from the icy water by local farmers and fishermen.
Some partially-filled drums remained floating, but most of the heavy water sank to the bottom of Lake Tinnsjø, where it remains today.
Poulsson and Helberg returned to the Hardanger Plateau in October 1944, where they joined Tronstad in Operation Sunshine, an attempt to preserve industrial infrastructure by frustrating Nazi ‘scorched earth’ practices as they retreated from Norway. Tronstad was killed on 11 March 1945 during a struggle with Nazi collaborators Torgeir and Johans Lognvik. He was given a military funeral, and received medals and awards from Norway, France, Britain, and the US.
Commemorations
A 1948 Norwegian-French film, Operation Swallow: The Battle for Heavy Water, was made on location in Norway and featured many of the participants playing themselves, including Haukelid, Helberg, Kayser, Kjelstrup, Poulsson, Storhaug, Torstein Skinnarland, Sørlie, and Storhaug. It also featured Frederic Joliot-Curie and Lew Kowarski, from Part 1 of this essay. It was the second-most popular film at the French box office that year. The 1965 British film The Heroes of Telemark, based in part on Haukelid’s 1954 memoir Skis Again the Atom, featured Kirk Douglas as the fictional Dr Rolf Pedersen, and Richard Harris as Knut Straud, based loosely on Haukelid. It takes a Hollywood-style approach to historical fact. ‘I hear they are spending 5 million dollars,’ said Haukelid during filming, ‘so it’s got to be spectacular and that means more fiction and less fact’.
In the BBC book accompanying Ray Mears’ 2003 documentary series The Real Heroes of Telemark, he explains that the 1965 film is a ‘travesty of the truth’, and that ‘the truth is far more captivating’. The six-episode TV drama Kampen om tungtvannet (The Heavy Water War or, alternatively, The Saboteurs) was produced by the Norwegian Broadcasting Company and first aired in 2015. The series was acclaimed for its quality of acting, cinematography, production, and direction and, though more accurate in its portrayal of events, it took enough licence likely to enrage a few historians.
Earlier this year, the efforts of the Norwegian commandos of Swallow and Gunnerside, and those who lost their lives in the failed Freshman operation, were commemorated by Princess Anne, who laid flowers at a memorial stone erected at Vemork after the war. She was accompanied by Jostein Rønneberg, son of Joachim, who had died in 2018 at the age of 99.
Jim Baggott is an award-winning science writer. This post is based in part on extracts from his book Atomic: The First War of Physics and the Secret History of the Atom Bomb 1939-49, first published in the UK by Icon Books and as The First War of Physics by Pegasus Press in the US. Atomic | Jim Baggott
Very riveting! Once I started reading I couldn’t stop.
Wow, that was even more exciting than Part 1. I thoroughly enjoyed this and throughout kept thinking the dramatic structure was perfect for a film or TV adaptation without changing a single fact. It has everything you could want for a WWII action/spy story.