The Telemark Raids

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Podcast Transcript

During World War II, one of the biggest concerns of the Allies was the development of a German atomic bomb. 

As such, the allies and various partisan groups in occupied countries made the destruction of anything related to the Nazi atomic program a high priority.

One place, in particular, was subject to allied bombing, commando missions, and partisan sabotage throughout the war. 

Learn more about the Telemark Raids and how Norway became an important front in the Second World War on this episode of Everything Everywhere Daily.


I previously did an episode on the Nazi atomic weapons program, or the lack thereof. 

The allies, working on their own atomic weapon, were concerned about the Nazis developing their own weapon. Before the war, many of the world’s greatest physicists were German, and the allies were certain that they were in a race to build an atomic bomb. 

It wasn’t that the Germans weren’t thinking about it, it was just that they never quite got as far as the allies thought they did by the end of the war. 

When the Americans built their atomic bomb, they did so through the separation of uranium isotopes. They went through the extremely difficult and expensive process of separating Uranium-235 isotopes from Uranium-238 isotopes. 

German physicists such as Werner Heisenberg knew of this option but figured it was far too difficult and expensive actually to do. In fact, after the Americans dropped the atomic bomb on Hiroshima, Heisenberg didn’t initially believe it because he thought the separation of Uranium isotopes would have been too hard to do.

German research pursued another option which was still difficult but not nearly as difficult as the path the Americans took.

Instead of separating uranium isotopes, you can put them in what is called a neutron moderator.  A neutron moderator is a substance that can slow down neutrons emitted via radiation. When the neutrons are slowed, they are more likely to produce fission. 

One of the best neutron moderators is heavy water. 

Heavy water is H2O but with the hydrogen atoms consisting of the isotope deuterium. Deuterium is a hydrogen atom with a neutron in the nucleus, whereas regular hydrogen doesn’t have one. 

If you can make a heavy water reactor, then you can produce plutonium which is much easier to separate chemically from uranium than trying to separate different uranium isotopes. 

Creating heavy water involves separating naturally occurring deuterium, which is found in very small amounts of water molecules. There are approximately 156 deuterium atoms per million hydrogen atoms.

Separating deuterium from regular hydrogen in water takes a lot of electricity. You basically perform electrolysis on water over and over as you separate out the heavier molecules. 

One of the best places in Europe to do this, where you can find ample amounts of electricity and water, was at the Vemork hydroelectric plant in the Telemark region of Norway. 

The Norwegians began the creation of heavy water there in 1935 before the war started. It was the only place in the world that was creating heavy water before the war started. 

Heavy water wasn’t something that could be created at a large scale. Even with one of the world’s largest hydroelectric plants, the amount of heavy water it could create was limited. In 1940, before the Germans invaded Norway, Vemork could only produce 10 kilograms or 22 pounds of heavy water per month.

The various world powers realized the value of heavy water and also the threat from Germany. 

Just prior to the invasion of Norway in early 1940, the director of the Vemork facility agreed to lend France 185 kilograms or 408 pounds of heavy water for the duration of the war. This was the entire supply of heavy water in the world at the time. 

This was in response to German companies offering to buy Vemork’s entire production of heavy water. In fact, they requested ten times the amount that they were producing at the time.

That water found its way to France, and then after the German invasion of France, found its way to Britain. 

When Germany invaded Norway in April of 1940, they found themselves in control of the only heavy water production facility in the world. 

German control of this facility deeply concerned the allies. They knew very well what heavy water could be used for, and eliminating the German production of heavy water became a top priority. 

The initial allied plan was to do what the allies did best: bomb it. 

The problem was the facility was not a very good target for bombing. 

As I mentioned in previous episodes, strategic bombing in World War II was extremely inaccurate. Hitting a concrete facility on the side of a mountain in an occupied territory would be much harder than trying to bomb a regular factory in Germany.

It was eventually decided to scrap the bombing mission and try a covert mission where they could destroy the facility from the inside. 

The mission took almost two years to plan. 

The first mission was a reconnaissance mission that took place in March of 1942. A single man, Einar Skinnarland, had sailed to Britain, received intense training for ten days, and then was parachuted back into Norway. 

He had contacts at the Vemork facility and was able to get an idea of what the defenses were like.

That summer, a four-man team of Norwegians commandos was trained in the UK. Everyone on the team was from that area of Norway, and they were trained in outdoor survival, sabotage, covert radio communications, and guerilla warfare.

This was given the codename: Operation Grouse.

On October 18, 1942, the four Norwegians were parachuted into Norway. They were actually dropped pretty far away from the target area so they would escape detection by the Germans. It took them two weeks to ski and walk cross country to get into position.

The Norwegians eventually made contact with the British, which would begin the next phase. 

They actually found the Vemork facility to be less heavily guarded than in earlier reports. The Germans most had older Austrian men guarding, and their numbers appeared to have been cut in half. 

On November 19, 1942, the British initiated Operation Freshman. This was to drop in British commandos and heavy equipment on a glider that would land on a nearby frozen lake. 

This was the first time the British had ever used a glider like this before.  Two bombers towing two gliders took off from Scotland. 

From the start, things didn’t go well. One of the bombers crashed into a mountain in southwest Norway, killing everyone on board. Their glider managed to avoid the mountain but still crashed, killing several. 

The other bomber couldn’t find the landing site because the radio beacons had failed. They eventually ran low on fuel and aborted the mission, but the tow rope of the glider broke, and it crashed not far from the location of the other glider. 

The Norwegians couldn’t get to the crash site, and the crash alerted the Germans. Eventually, all the surviving British commandos were captured and executed. 

In addition to losing all the commandos from Operation Freshman, it also alerted the Germans to the fact that the British were interested in the heavy water facility. 

While Operation Freshman was a disaster, all was not lost. The team from Operation Grouse was still on the ground. 

The British launched Operation Gunnerside on February 16, 1943. This abandoned the gliders and went back to what they knew worked: parachutes. 

Six more Norwegian commandos were parachuted in, along with additional supplies.  They eventually found the Operation Grouse team, who had been hiding for several months in the wilderness during the Norwegian winter.

Now with eleven Norwegian commandos on the ground, they had a team that could assault the facility. 

The problem was the Germans had improved security. They placed mines around the facility as well as searchlights. 

Thankfully, the Norwegians had an inside man in the facility who managed to get them inside via a tunnel for cables and then through a window. 

Once inside, they didn’t encounter anyone other than a custodian who was happy to help the Norwegian commandos.

They planted bombs on the electrolysis tanks with a delayed fuse and left various British items, including weapons, on the site so it would appear as if it were a British action. This way, the Germans wouldn’t take it out on locals if they thought it was Norwegians who were part of the raid. 

They managed to blow up all the tanks and their entire 500-kilogram supply of heavy water. The German ability to produce heavy water was crippled. 

The Norwegian commandos managed to escape without notice. Five of them managed to ski to safety in Sweden, two went to Oslo, and four stayed in the area to continue working on sabotage. 

The problem was the damage they did was only temporary. By April, the Germans had the facility back up and running. 

The British felt another commando raid wouldn’t work with increased security around the facility. They decided to give bombing missions another try. 

The Americans began running bombing missions over the city of Rjukan, where the facility was located. 

In early November, there was a massive daylight bombing raid of 143 bombers who dropped over 700 bombs. The earlier concerns about the effectiveness of bombers proved correct. 600 of the bombs missed, and while damage was done to the facility, it wasn’t enough to shut down operations. 

Further nighttime raids that month eventually convinced the Germans to end heavy water production at the facility. Norway simply couldn’t be defended as well from air attacks as Germany could. So to that extent, the raids were a success. 

However, 20 Norwegians were killed in the bombing. 

The Germans were going to take all the equipment and the heavy water which they had produced and ship it back to Germany. 

Word of this eventually made it to Knut Haukelid, who was the only commando still on the ground in the area. 

He devised a plan to sink a ferry that would be transporting the rail cars across nearby Lake Tinn as they were en route to Germany. Lake Tinn is one of the deepest lakes in all of Europe. 

Haukelid recruited two locals to help with the mission. One of them knew one of the crew on the ferry, the SF Hydro. He managed to sneak on board and planted 8.5 kilograms of plastic explosives on the keel of the ship. 

A little after midnight on February 20, 1944, the ferry pulled out of port and the bomb was detonated. The ship sank to the bottom of the lake along with all of the heavy water onboard. 

This mission came at a steep cost, however. 14 Norwegians were killed along with four German soldiers. 

This pretty much ended Germany’s heavy water program and any attempts at developing a nuclear reactor. 

In 2004, divers went down to the wreck of the SF Hydro and found the still sealed barrels of heavy water. They tested the water and found that it didn’t have near the levels of deuterium that the previous heavy water had. 

Even if it was at the appropriate quality, it turned out that the Nazis only had about 10% of the amount of heavy water necessary to create a nuclear fission reactor.

Today, you can visit the city of Rjukan and the Vemork Facility. I visited several years ago, and there is actually a lot of history in the region. The Vemork plant was actually the largest hydroelectric plant in the world when it opened, and it was one of the first places to produce fertilizer based on the Haber-Bosh Process. 

You can also take a very similar ferry ride on Lake Tinn as the SF Hydro took, and they have an extensive museum that gives background on the raids. 


It is about a 2.5-hour drive from Oslo if you are in the region. 

The Telemark Raids have been popularized in media. Several movies and documentaries have been made, most popularly “The Heroes of Telemark” from 1965, starring Kirk Douglas and Richard Harris.  

While Operation Freshman was a disaster, Operation Gunnerside was one of the most successful commando raids in World War II. It remains the most celebrated Norwegian military operation of the entire war. 

Its success was all due to a team of Norwegians who were willing to pay the ultimate sacrifice to prevent Nazi Germany from developing the ultimate weapon.