By Chuck Lyons
On an overcast February night in 1943, nine British-trained commandos worked their way down the icy slope of a ravine in southern Norway. In addition to skis and packs, each man carried chloroform to silently disable any guards he came across. The wind was blowing in strong gusts.
At the bottom of the ravine, hidden in the darkness, the men could see the lights of the factory above them, a bridge over the river, even the tiny silhouettes of German guards. They crossed the Mana River at a ford that had been located earlier, slipping occasionally on ice that was hidden below the surface of the water. Once across, they started up the other side of the ravine, finally reaching an unguarded railroad track, which they followed to massive metal gates. Covered by the sounds of the factory, one of the commandos snipped the lock on the gates, and they were in.
Four of the men took positions on guard just inside the gate, with a fifth man further inside the factory. The remaining four men split into two pairs, each party carrying explosives and pre-cut fuses.
The commandos had infiltrated the Vemork chemical plant of the Norsk Hydro Company, the only facility in Europe producing heavy water (deuterium oxide), a “neutron moderator” that enhances nuclear reactions. Deuterium oxide was essential to the production of an atomic bomb, a project Germany had been working on quietly since 1939.
Prior to their occupation by the Germans on April 9, 1940, the Norwegian government contacted French military intelligence for the removal of the plant’s total inventory of heavy water, about 408 pounds. It was first shipped to Oslo, then to Scotland and, finally, to France. When Germany invaded France a month later the heavy water, along with some scientists, was hurriedly moved from France to England.
For now heavy water had been kept out of German hands—out of the Nazi atomic bomb project—but the plant remained and was still functioning. It had to be destroyed.
On October 19, 1942, a four-man team of Norwegian commandos, trained by Britain’s Special Operations Executive (SOE), gathered in London to plan an attack on the plant. Maj. Leif Tronstad, a chemistry professor in civilian life, planned the attack and the proposed sabotage. The Norwegians chosen for the mission were people local to the area and with extensive outdoors experience. SOE nonetheless put them through added outdoor training in Scotland, where they were also trained for operations in occupied territory, sabotage, radio communications, and “irregular warfare.” At first, the team leader alone was briefed on the proposed mission while the other three men then involved were led to believe they were preparing for a training mission with the Norwegian resistance codenamed Operation Grouse.
After two failed attempts—one due to severe weather and the other an airplane engine problem—the Grouse team was finally parachuted into Norway on October 18, 1942.
“We ended up in rough terrain, in boulders and rocky mountain slopes,” Claus Helberg, a member of the commando team, later wrote. “But all four of us plus our 12 containers with food, equipment, weapons, and ammunition landed nicely. Even our radio transmitter seemed to have survived the rocky landing.”
They were in Norway, but continuing harsh weather meant the drop zone was moved 60 miles from where it was originally planned.
Once on the ground, the other three members of the assault team were told the real aim of the mission: they were to hit the plant at Vemork, destroy whatever heavy water was in the plant, and do as much damage to the facility as they could.
The men then gathered the supplies and equipment that had been dropped with them. It took them two days to find everything, and on their third night they began hiking east toward the plant carrying what they could. They hid the rest of their supplies. That night the weather switched to snow, but the snow on the ground remained bad for skiing. Every day was a struggle as they each had to carry half their equipment ahead, then doubled back to get the other half.
“On good snow, an experienced skier would have covered that distance in a day or so,” Helberg wrote. It would take the commandos more than two weeks.
Near the plant, the commando team took refuge in an abandoned cabin to wait for the British engineers to be brought in by glider to do the actual demolitions. The commandos also contacted local Allied sympathizers who provided news and some needed supplies.
“We were to find a good landing site for two British gliders,” Helberg wrote, “[and] reconnoiter the plant in advance.” They found a suitable site for glider landings near the Skodal Marshes.
The German military had successfully used an airborne attack force, paratrooper, and gliders, as early as the Battle of France in 1940; their success was quickly copied by Britain with Prime Minister Winston Churchill ordering the development of a 5,000-man parachute and air attack unit. During planning for this force, it was quickly decided that gliders would be important components for moving men and heavy equipment.
Tested in November 1940, Britain’s first military glider, the Hotspur, was only able to carry eight soldiers. In February 1941, the RAF put in an initial order of 400 for the Horsa glider, which had a capacity of 30 troops. The first prototype was tested and approved in September, going into production using woodworking facilities that would not have to be diverted from other wartime uses.
The Horsa was first used in this ill-fated mission to drop Royal Engineers into Norway dubbed Operation Freshman. On November 19, the Royal Engineers left the RAF Skitten station in Scotland aboard two Airspeed Horsa gliders, each towed by Handley Page Halifax bombers. Each glider carried two pilots and 15 Royal Engineers of the 9th Field Company, 1st British Airborne Division. Once the planes were over Norway, weather conditions worsened with severely limited visibility, and one of the Halifax bombers crashed into a mountain dragging its glider with it.
The other Halifax arrived at the area but could not find the landing zone.The bomber pilot eventually aborted the mission and headed for home. Heavy turbulence caused the tow rope to break and the second Horsa crash landed not far from the first glider.
Twenty-three survivors from the two crashes were captured and turned over to the Gestapo. They were interrogated, tortured, and eventually executed under Hitler’s infamous Commando Order—issued a day before the original group of Norwegian commandos had landed. That order specified that all Allied commandos captured by German forces would be killed at once without trial, even if they were in uniform or tried to surrender.
When the four-man Grouse team received the news of the crashes via radio, they moved north to a second cabin hideout to await further orders. The first cabin had been only three miles from a German camp. Now they were stuck in the mountains to survive as best they could, while also dealing with German forces that were on high alert after the plane and glider crashes and were searching local villages for survivors.
For two weeks the commandos moved further into the mountains, surviving on rationed oats, margarine, sugar, and Iceland moss that they pulled from beneath the snow. On Christmas Eve one member of the party killed a reindeer, and the men celebrated the holiday with fresh meat. For the next two months, the men survived on reindeer meat.
Defenses at the Vemork plant had also been stiffened, with double the number German guards brought in to replace the Austrians who had been sentries at the facility. All were guarding the single 246-foot bridge that spanned the 660-foot-deep ravine in front of the plant, which the German command considered the only access. They further considered the ravine to be uncrossable by any other means. Additional mines and floodlights were also installed.
Finally, during Operation Gunnerside on February 16, 1943, three months after the disastrous bomber and glider mission, a second team of six Norwegian commandos was parachuted into Norway about 30 miles north of the original “Grouse” group, now referred to as the “Swallow team.” The bomber pilot was again unable to find the designated drop zone, and shortly after the commandos plummeted to ground a storm struck. The Gunnerside group, SOE-trained Norwegians chosen after the use of Royal Engineers and gliders was abandoned, took refuge in a nearby cabin before venturing out to connect with the Grouse/Swallow team.
Together, the two commando groups developed final plans for their assault. They could fight their way across the bridge, which would be noisy and would alert the Germans to their presence, or descend 600 feet into the gorge, cross the icy Mana River, and scale the cliff on the other side, a feat that local people and the Germans believed was impossible. They chose the second option, and Helberg made a lone daylight scouting foray to decide if their plan was possible and to work out a route.
On the night of February 27-28, the combined team of nine men approached the Vemork plant and the ravine. The raiders wore British uniforms and carried their skis and packs. The wind and the ice along the ravine made the going rough, but the men got down to the bottom without too much trouble. The river had risen from the time Helberg was there the day before, and the water was flowing over ice. However, the commandos managed to cross and start up the other side, making their way to the rail line Helberg had discovered and into the facility.
Once there, they split into a covering party and a demolition party. The covering party took positions from which it could attack if the Germans discovered the infiltration. If there was no discovery, the covering party was to stay in place until they heard the explosions, then withdraw. If the Germans discovered what was happening and sounded an alarm, the party was to attack the guards at once. If something unexpected happened that disrupted the attack plan, everyone was to act on his own to complete the mission as best he could.
“I was with the cover party,” Helberg wrote. “We covered the German guardhouse and the entrances of the factory. Fortunately, we did not see a single guard. The noise from the factory was quite loud, and there was no other sound. It was pitch dark, and, even if a German had come, I do not believe he would have seen us leaning against the factory wall.”
The attack party forced a second gate open and left one man on guard there. The remaining four members of the party split into two pairs, each carrying a complete set of explosives in case one of the two teams did not reach the heavy water. The men were familiar with the plant’s layout from plans that had been obtained by a collaborator and headed straight to a cellar door. They found it locked and tried an entrance on the floor above. That too was locked. The cellar door was to have been left unlocked by an agent in the plant, but he had fallen ill and did not come to work that day. The commandos could see a man working in the cellar, but no guards were visible.
There was one more alternative. The diagrams of the plant showed a narrow shaft into the cellar the commandos had been told to use as a last resort. They found the hatch to the shaft, and it had been left unlocked as they had been promised. One of the two pairs of saboteurs entered the shaft and crawled forward over a mass of wires and pipes, pushing their sacks of explosives ahead of them. At the end of the shaft, they found a ladder and slipped into the plant’s basement.
There they encountered a frightened night watchman, who was held at gunpoint by one member of the demolition party as the other man placed the explosives they had brought. Meanwhile, the second team had found a window into the area, broken the glass, and entered. The men finished setting their charges and shortened their planned fuse time of 2 minutes to 30 seconds, fearing they wouldn’t hear the explosion if they got too far away. A Thompson submachine gun was purposely left behind as a sign the sabotage was done by British commandos in hopes of mitigating any reprisals against the local community. The night watchman was told to run upstairs as fast as he could, and the saboteurs rushed back through the steel cellar door into the night. They were about 20 yards away when they heard an explosion muffled by the noise of the power station and the thick concrete walls.
“[It] was not very loud,” recalled one of the men. “It sounded like two or three cars crashing in Piccadilly Circus.”
But the plant’s entire inventory of heavy water, some 1,102 pounds, was flooding the basement and flowing toward the drains. The essential electrolysis chambers that produced the heavy water were also severely damaged. Meanwhile, the four members of the covering party who had been left on guard waited for a German reaction. They saw only a single German soldier appear in the doorway of a nearby hut. He swept the area with a light, which came dangerously close to the Norwegians, turned, and went back into the hut. Unknown to the saboteurs at the time, dull thuds such as that caused by the explosives were common at the installation. Small explosions occasionally were caused by the machinery, and cracking ice or thawing snow near the plant caused similar noises.
Eventually, the damage was discovered, and 3,000 German soldiers were dispatched to search the area for the commandos. But the entire commando party was able to escape, five of the men skiing 249 miles to Sweden wearing British uniforms and carrying British weapons. Another member of the team went alone to Oslo and then on to Sweden and England. Two others went west and set up a headquarters for resistance forces in the Vinje region; one of those men was back in England by Christmas, while the other stayed in Norway until the end of the war. Another member of the group set up a radio station in the Hamre Mountains and ran it for the rest of the war.
The sabotage mission had succeeded, but the damage was repaired. By April, the Vemork plant was back in operation. And by the fall, the Allies were ready to hit it again. This time they came by air. The need for ground assaults was reduced from a year earlier as there was now the alternative of night bombing, which had previously been unrealistic owing to German air supremacy. Several Allied bombing raids were launched against the plant, including a massed daylight raid of 143 U.S. Army Air Forces Boeing B-17 Flying Fortress heavy bombers that unloaded 711 bombs on the plant and its vicinity. Only 18 of these bombs hit the Vemork facility, but it was enough to heavily damage the plant and its power station. The bombs also destroyed about 132 pounds of heavy water, a little less than a month’s production. Twenty-two civilians were killed, and six civilian residences destroyed.
On November 16 and 18, 1943, a total of 35 American Consolidated B-24 Liberator bombers attacked the hydroelectric power station at Rjukan, an attack that convinced the Germans that the Vemork facility was vulnerable to future air attacks. In early 1944, they decided to abandon the plant and move its remaining stocks of heavy water and critical manufacturing components to Germany. Resistance fighters also attacked a shipment of deuterium oxide sent from the plant as it was ferried across Lake Tinn, sinking the ferry and its cargo in 1,400 feet of water on February 20, 1944.
Nazi plans for an atomic bomb were all but scuttled. The project sputtered along before finally stalling completely. The electrolysis equipment from the Vemork plant was found disassembled in Germany after the war.
“In modern history, there are few examples of such small works of sabotage leading to such dramatic effect,” one historian wrote. “Had the Nazis worked [on an atomic bomb] unhindered, the world’s first atomic mushroom cloud may have loomed over London by the mid-1940s.”
Chuck Lyons has written for WWII History and numerous other periodicals as well. He lives in Rochester, New York.
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