Operation Gunnerside

Despite the failure of Operation Freshman, the British and Americans remained determined to destroy the installation at Vemork. Following the suggestion of former plant manager Jomar Brun, who had meanwhile fled to Great Britain, the British decided the next attack could be best carried out by a small group of Norwegian saboteurs. Lieutenant Joachim Rönneberg was appointed leader of the operation; he was selected by S.O.E. for his balanced personality and good qualities of leadership. He was to recruit a group of five volunteers from Kompanie Linge in Glenmore camp, an army unit consisting of Norwegians who had fled their home country. He selected Lieutenant Knut Haukelid, Sergeant Fredrik Kayser, Lieutenant Kasper Idland, Sergeant Hans Storhaug and Sergeant Birger Strömsheim. They were given special training for which even a scale model of the electrolysis plant was built at the S.O.E. facility in Brickendonbury Manor in Hertfordshire. They had to learn every detail by heart. After the war, Rönneberg declared about this: "With the arrival of Jomar Brun, all blueprints of the factory had also arrived and I can safely state that not a single operation that has been carried out from England in this period, had so many details at its disposal than ours. Not one of us had ever been inside the plant but when we left England, we knew more about it than anyone else."

The drop in connection with Operation Gunnerside was postponed frequently because of bad weather. On one occasion, they had departed but had flown back to Scotland because the navigator could not find the drop zone. For the next drop, it was agreed upon the men would jump anyway, even if there was no contact with the reception committee. On February 16th, the weather was favorable. Tronstadt addressed the men shortly before departure: "Unfortunately I cannot tell you why this mission is so important but if you succeed, you will live forever in Norwegian history, so good luck and be strong." Prior to departure, they were each handed a suicide capsule. The drop proceeded very well. They came down at Lake Stricken, some 31.07 miles from the Fetter cabin. They recovered the supplies from the 11 containers that were dropped with them. They took some of it along and buried the rest on the spot. They found shelter in a cabin, designated the Jansbu cabin, standing at some miles from the lake. They did not know exactly where they were. The area was difficult to identify as everything was covered by a thick layer of snow. The next day the men tried to contact Poulsson but they had to abort the attempt because of a snow storm. This storm lasted no less than five days. Only then could the group embark on the journey to the Fetter cabin. A local poacher acted as their guide.

As soon as Poulssons and Rönnebergs men had met they started preparing for the operation. The team was split in two, one would occupy itself with the sabotage, the other was to provide cover. Haugland and Skinnarland left for the Jansbu cabin in order to maintain radio contact with London. There were a few ways to approach the plant. They could take the route across the suspension bridge but it was heavily guarded. They also could use a narrow trail that ran around the mountain via which they could reach the factory from above. This route was also rejected because of the presence of mine fields. After a reconnaissance, Helberg came up with a new idea. He suggested to descend into the valley, climb the hill on the other side and then enter the building by way of an unguarded railway entrance. The ravine measured some 656 feet in depth. Helberg reconnoitered the route through the valley. He discovered both slopes were covered in trees and bushes and contained many fissures. Experienced as they were they should be able to descend and climb these slopes. Helbergs idea was accepted. They depended heavily on the weather. If much snow would fall, their supports on the slopes would disappear. In case a warm squall would blow through the valley, the mission would have to be cancelled also because of the amount of melting water streaming down the slope.

Shortly before departure, Poulsson drew the mens attention to Hitlers Kommandobefehl. He advised them to commit suicide if they risked being taken prisoner. In the night of February 27th, 1943, the sabotage team left the Fjosbudalen cabin on skis, which had been chosen as the spring board for the operation. They took a steep downhill route. Poulsson noticed from the warm and humid air a squall was approaching. If it really started blowing, this would make the snow soft and slushy, making skiing difficult. Frozen rivers would be covered in water making crossing them even more difficult. The team of skiers were already impeded by the bad snow conditions. On a few occasions they sank down to their waist. At their depot near a dirt road, they left their skis, coveralls and rucksacks behind. They were now dressed in British uniforms. They hoped the raid on the installation would be considered a British operation and so prevent reprisals against the local population. The men were armed with a Thompson submachine gun, a Colt .32 of .45 caliber pistol and hand grenades. Two of them carried the explosives. When they descended into the valley, they saw thaw had set in, melting water was coming down the slopes and there was water on the frozen lake. They climbed the 656 feet high slope on the other side. After an exhausting trip of three hours they reached the railway line and approached the plant in a spread out formation.

At 00:30 hours, the sabotage team had reached the entrance to the plants premises. Kjelstrup broke the padlock of the gate that gave access to the railway line. The others waited a few hundred yards away. After this was completed, Kjelstrup left the premises to keep an eye on the German guards near the locks, some 300 yards up the mountain. Helberg took the watch near the gates to cover the withdrawal. Storhaug kept an eye on the guards near the bridge. Haukelid and Poulsson went to the German barracks adjacent to the plant and hid behind a few storage tanks. Should the Germans come out in case of an alarm, they would open fire on them. Rönneberg, Kayser, Strömsheim and Idland approached the building housing the electrolysis plant. The door was locked but Rönneberg and Kayser managed to enter the building through a cable duct. Brun had drawn their attention to the existence of this inspection duct one man at a time could crawl through. They lowered themselves through a man hole. They found the door to the electrolysis tank unlocked. A Norwegian worker was overwhelmed and he handed them the key of the door to the inner yard. The commandoes had to leave the plant by this door after their sabotage. Strömsheim and Idland failed to find the inspection duct. In order to gain access to the building, they smashed a basement window. This caused some consternation because Rönneberg initially thought they had been discovered by the Germans. When this proved not to be the case, the operation was continued. 20 packs of 9.92 lbs nitroglycerine, also known as bread rolls, were placed on the electrolysis tanks by Rönneberg and Strömsheim.

Rönneberg left a few parachutist badges and a Tommy gun behind to create the impression, the raid had been carried out by British commandoes. When Rönneberg was about to light the fuse, he heard foot steps. It turned out to be the foreman of the night inspection team. This man was terrified when confronted with the commandoes but did not raise the alarm though. The saboteurs ordered the two employees to go to the second floor. Rönneberg lighted the fuse and the commandoes left. After two minutes, at about 01:15, the charges exploded. The force of the explosion was exactly right: all 18 production tanks were destroyed. The bottom had been blown out, the electrode heads were completely destroyed and the walls of the tanks had been torn open. All tanks would have to be replaced. As a result of the explosion, the stock of about 132.06 gallons of heavy water had also been lost. Alf Larsen, chief engineer of the plant, described the situation as follows: "When I entered, I noticed that all cells had been blown and that the bottoms had been blown out. The entire room was filled with water vapor, also because all water pipes had sprung leaks from flying shrapnel. It felt like standing in a shower."

The men embarked on their return journey. The trip through the valley went well. Crossing the river was tricky because of the floating chunks of ice. Rönneberg and his team had to step from one ice floe onto the other.

The Germans were not alerted immediately. The guards were used to explosions as hydrogen gas was sometimes ignited in connection with experiments to acquire heavy hydrogen. Only after the men had crossed the river, the alarm was raised. The Germans assumed the men were still inside or around the factory. They considered it impossible the saboteurs had come through the valley. A search was started in which 3,000 soldiers participated.

It was intended the saboteurs should try to reach Sweden after the raid. Helberg, Kjelstrup, Haugelid and Haugland would stay behind in Norway and go into hiding. They returned to the Fetter cabin. Rönneberg, Idland, Strömsheim, Storhaug and Kayser would go to Sweden. They took a trip of 248.55 miles through inhospitable country. They were forced to spent several nights in the open in wet sleeping bags and were faced with shortage of food and bad snow conditions, making skiing difficult. Nonetheless, they reached Sweden after 18 days. They told Swedish authorities they belonged to a resistance group and risked being taken prisoner. Their story met a lot of disbelief. In particular the fact they were wearing identical clothes and shoes raised suspicion but they were admitted nonetheless. Rönneberg and his team were flown to Great Britain, Poulsson and Helberg went to Oslo separately. Haugland, Haukelid and Kjelstrup remained on the Hardanger plateau.

The Germans assumed, the raid had been carried out by British commandoes in cooperation with the Norwegian resistance. Wilhelm Redies, the Gestapo chief in Norway, threatened with reprisals. He had 10 hostages taken among the civil inhabitants of Rjukan. Generaloberst Nikolaus von Falkenhorst (Bio Von Falkenhorst), commander of German armed forces in Norway prohibited this however. He considered the sabotage a military operation and "a beautiful piece of craftsmanship", so it was said. The commander of the guards of the Vemork installation was transferred to the eastern front though by personal order of Von Falkenhorst. A few additional protective measures were taken. The Rjukan railway was closed to civilian traffic because the Germans thought the saboteurs had made use of it. Roadblocks were erected on the highway to Vemork. The mine fields were expanded and the guard around the factory was doubled. A curfew was proclaimed in Rjukan and a license was required henceforth to make phone calls within the region.

A sudden storm prevented the Germans from launching a massive search on the plateau, although they did make plans. The Norwegian commandoes who had stayed behind in the region were tipped off by the resistance about the imminent German search. Therefore they moved to one of the most inaccessible areas of the mountain range. The German search was carried out with little coordination though.

Helberg decided to travel to Rjukan from Oslo in order to retrieve weapons and explosives that had been left over from Operation Gunnerside and hide them in another location. During his ski trip across the Hardanger plateau, he was discovered by the Germans. A pursuit lasting several hours ensued. Helberg managed to evade a number of soldiers. He managed to inflict serious injuries on his last pursuer, enabling him to escape. Owing to his exhaustion, he fell into a ravine though, breaking his left arm in the process. He found shelter with a shop keeper he knew. He accosted a German Feldwebel and told him he had voluntarily assisted in the German search and had broken his arm. The Feldwebel sent him to a military physician, who gave him an emergency band aid and sent him off to Oslo. Helberg and other guests of Hotel Bandaksli in Dalen, where he was staying, were arrested later on and deported to Grini concentration camp by the Germans. Helberg managed to escape from the bus. He found shelter with a family. The next day he went to a hospital in Drammen where he remained for a few weeks. In April he fled to Sweden.