At the end of the Second World War, the German armed forces had large quantities of ammunition in Norway. It was stored in various units and large warehouses.

In addition, there were explosives belonging to the police and Organisation Todt – a German semi-military organization involved in construction and engineering. There were also components and ammunition stored at the ammunition factory Raufoss ammunisjonsfabrikker.

But how much ammunition was there, actually, and what should done with it?

One of the few people who had some sort of overview was Colonel Büttner, who in the summer of 1945 was interned in a prison camp in Lillehammer. In a letter to the Norwegian authorities dated 18 August 1945, he described the situation regarding the ammunition.

At the end of the war, the German army and coastal artillery troops had 90,000 tonnes of ammunition stored in Norway, not including munitions from the other branches such as the navy and Luftwaffe.

The stockpiles Büttner knew of included everything from small arms to large artillery shells. The colonel estimated their value at NOK 780 million, which corresponds to NOK 21.3 billion in today’s money. Could it have been possible for him and other Germans to assist Norway in handling and dismantling this ammunition?

On 19 September 1945, the Army Ordnance Corps stated that it would be too dangerous to use Norwegian workers for dismantling ammunition. Norway also lacked people with the right expertise. However, if the Germans could do the work, it would save a lot of steel and other materials.

In October 1945, the Norwegian High Command concluded that they did not want to pursue the proposal. The ammunition was to be handled and dumped in accordance with the guidelines set by the Allies. In addition, Norway needed all the Norwegian workers it could get to help rebuild the country.

The assessment of whether German soldiers could be used for dangerous work was also sensitive due to the Geneva Convention.

“Norway used German soldiers to clear minefields and dump explosives in fjords and lakes. This was dangerous work that resulted in many deaths,” said Professor Mats Ingulstad at the Norwegian University of Science and Technology (NTNU).

In the book Da freden brøt løs (When peace broke out), Trond Risto Nilssen writes that 170 Germans died in this mine-clearing work.

Büttner referred to Germany’s experiences from the First World War, noting that there was always a risk that ammunition dumped in natural environments might resurface. Ingulstad explains that the Norwegian Armed Forces had observed the same phenomenon, for example around the Trondheim fjord in the summer of 1945. Hand grenades and other explosives had been dumped here and could now be reached at low tide or washed ashore elsewhere.

The ammunition contained valuable metals, but instead of recycling it, the authorities chose to dump it in Lake Mjøsa, other lakes, and the sea.

In the Mission Mjøsa research project based at NTNU Gjøvik, the history of the dumping is being charted as part of the ongoing work. Ingulstad believes that pollution from military activity and ammunition dumping, which is now being discovered in several places in Norway, could challenge the defence industry and the need for rearmament. There will be more about this towards the end of the article.

Master’s students, PhD research fellows and postdoctoral fellows are currently working to map the causes, extent and consequences of the dumping in Lake Mjøsa and other locations in Norway. The letter from Büttner was discovered by a master’s student at the Department of Historical Sciences.

“This is a type of research we could call applied environmental history,” said Ingulstad, who believes that the study of history is important for understanding the origin and scale of major societal problems, and for helping solve them together with researchers from other fields of study.

Raufoss ammunisjonsfabrikker (RA) became part of a national rearmament strategy. What consequences did this have for the surrounding inhabitants, local development and the environment? In a new four-year project called Eksplosiv Arv (Explosive Legacy), NTNU, Mjøsmuseet – the Mjøsa Museum and Vestre Toten Municipality will collaborate to find answers.

Why was Büttner so focused on recycling the ammunition that he contacted the Norwegian authorities?

“We can only speculate, but we are now trying to find more information about him in German archives. Perhaps he was thinking as an environmentalist who realized that recycling metals was a sensible solution. The Germans were very focused on this, even though dumping was easier. In addition, he was of the opinion that he spoke reasonably good Norwegian, having been in the country since 1940. Meanwhile, large parts of Germany lay in ruins. He probably also knew that he risked a prolonged stay in a prison camp. If he came from one of the areas occupied by the Soviet Union, what later became East Germany, it may well be that continuing to work in Norway was more appealing, even if it was dangerous,” explained Ingulstad.

The German arms industry needed metals such as copper, lead and zinc. Under the Nazi rule, recycling centres were established to reduce the need for imports. Without sufficient metals within its own borders, Germany saw the potential of recycling.

They expanded capacity, trained specialists and collected scrap from households and companies. This was a strategy they brought with them to the countries they occupied, including Norway.

Ammunition was also recycled, and any surplus was regarded as a valuable resource.
Approximately six months after the invasion of Norway, the Germans launched the Metal Mobilization initiative – a campaign to collect and recycle scrap metal. In October 1941, the Metal Central was established to organize this process more systematically.

The collection that took place in Norway was often carried out by Norwegian scrap dealers. Norwegian companies melted down scrap metal and produced new materials, although much of what was collected was sent directly to Germany. There were monthly campaigns in Norwegian cities, collecting everything from motor vehicles to cutlery.

The collection was formally overseen by the Norwegian Ministry of Trade, which was under the control of the German occupying forces.

Raufoss Ammunisjonsfabrikker (RA) was an important actor in the recycling efforts. The factory had been producing ammunition since 1896 and had its own metalworks and equipment for processing scrap metal.

“The recycling that took place at RA was coordinated by the Metal Central, and the factory regularly reported on the processing of scrap metal,” said NTNU historian Simon Renner.
RA processed scrap steel, including scrap metal from other Nazi-occupied areas. Bronze and other metals were also recycled.

The Germans almost tripled their ammunition production at RA from 1940 to 1945. They produced heavy artillery shells and ammunition for rifles such as the Krag–Jørgensen and Mauser machine guns.

At the end of October 1942, an explosion occurred during the dismantling of shells at RA, and a Norwegian worker was killed. The ammunition was from the First World War and had been brought there from Belgium. The accident occurred while workers were handling 7.5-centimetre high-explosive ammunition. The raw material in the shells was to be recycled, and the fuses had to be unscrewed.

“The work could be dangerous, and production defects and damage meant that not all ammunition could be recycled. In the spring of 1943, the Germans began dumping ammunition from RA into Lake Mjøsa,” explained Arne Julsrud Berg, Director of the Mjøsa Museum (Mjøsmuseet).

The Germans considered the work so dangerous that these shells had to be disposed of. Three German soldiers supervised as the passenger ferry Mjøsfærgen was requisitioned and employees from the Armaments Division carried out the dumping in Lake Mjøsa.

After the war, the dumping of ammunition and other military-related material from RA into Lake Mjøsa was organized systematically by the Norwegian authorities. Permission was granted by the Explosives Inspectorate and the Ministry of Justice. The Explosives Inspectorate was the precursor to what is now called the Norwegian Directorate for Civil Protection (DSB).

“It is unclear when this really began, because parts of RA’s archives have been removed,” said Ingulstad.

Quite soon after the war, local newspapers reported on children playing with German landmines on the beaches in Gjøvik, and fishermen finding ammunition in their nets.

In response, the military police said that what had been dumped was harmless. It was also stated that dumping at a depth of 420 metres in Lake Mjøsa posed no danger – nature would take care of it.

Over time, there were increasingly more media reports on the matter, and the problem was also raised in the Norwegian Parliament – the Storting. This is part of the reason why the Norwegian Defence Research Establishment and NTNU have surveyed parts of the bottom of Lake Mjøsa.

It has been widely reported that, during certain periods, three to four lorryloads of ammunition were dumped into Lake Mjøsa each week. How many weeks per year this went on for is uncertain, since the logbooks that recorded the dumping have been lost. However, it is known that the dumping took place over a period of 20 to 30 years.

Ingulstad hopes that the media attention and the discussion about whether to press charges, which Gjøvik municipal executive committee is currently considering, may lead to the documents resurfacing. He also encourages the leadership of today’s Nammo to make it clear to former RA employees and others in the local community that speaking out about the dumping is both important and the correct thing to do.

“We need to understand the extent and know where to search in order to be able to find the ammunition. The understanding of environmental impacts was different back then. The purpose of the research and investigations is not to discredit those who were acting on the basis of a completely different platform of knowledge. Instead, addressing past misjudgements will be important for ensuring the industry’s legitimacy going forwards. A detailed survey is now required to assess potential risks of pollution and accidents in the future.

Researchers estimate that between 2000 and 3000 tonnes of ammunition have been dumped at the bottom of Norway’s largest lake. This estimate is based on the section of the lakebed that has been surveyed so far. Not all of Lake Mjøsa has been surveyed yet, and Mats Ingulstad and Arne Julsrud Berg therefore believe that the actual figure could be significantly higher.

Is it dangerous that there is ammunition down there?

“More research needs to be done before we are able to give an accurate answer as to what should be recovered and what it is safest to leave in situ. “The ammunition can corrode, become more unstable and harder to handle. Sediments on the lakebed can cover the objects, but this depends on the conditions at the bottom of the lake and in the water column above. Ammunition that has been lying in water for 80 years can still be just as dangerous as when it was first dumped, and in some cases, it may be more liable to detonate than it was in 1945. We also see clear signs of corrosion, even in freshwater, which makes the ammunition unstable and unpredictable,” explained Ingulstad.

In addition, no one knows the amount of heavy metals potentially leaching into Lake Mjøsa, which is a source of drinking water for 150,000 people. The water from Lake Mjøsa flows downstream into the Vorma and Glomma rivers, and on into the sea.

In the research part of the Mission Mjøsa project that focuses on technology, samples are being taken this autumn from the lakebed around the artillery shells. The goal is to investigate how much the ammunition has deteriorated and whether it poses a pollution risk.

The dumping of ammunition must be viewed in light of the knowledge and attitudes that existed immediately after the war. At that time, there were different rules and expectations regarding the natural environment and risk.

The dumping was carried out from a private boat that Raufoss ammunisjonsfabrikk had rented. The Mjøsfærgen ferry was also used for dumping, until passengers began expressing concerns about safety. As a result, the factory started using its own boat.

Traces at the dumping sites – such as marks left by grappling hooks – suggest that there have been attempts to retrieve the ammunition.

“We see signs and have indications that certain groups are actively trying to retrieve military equipment and explosives,” said Ingulstad.

He believes this makes the dumping relevant in the current debate about weapons production:

“Thousands of tonnes of ammunition in Lake Mjøsa and other lakes are a societal problem that will not become easier to resolve over time – quite the opposite. This historical legacy must be taken into account when discussing the defence industry and the ongoing military rearmament. You could call it an explosive legacy,” said the professor.

“The main task of the Norwegian Armed Forces has been to carry out their military mission. But neither they nor society at large have paid enough attention to the environmental problems associated with war and ammunition production,” emphasized Ingulstad.

Clean water is also a matter of emergency preparedness. War and military activity pollute the environment, contribute to climate change, and increase the risk of natural hazards in the areas where the Norwegian Armed Forces operate. They also impact the security of local and global supply chains.

“This challenges both military logistics and operations, and has previously been under-communicated. Not taking the environment into account can also undermine the legitimacy of the Norwegian Armed Forces. So far, neither the state nor the Norwegian Armed Forces have properly acknowledged responsibility for the dumping or allocated sufficient resources for any type of clean-up operation. The new wave of military rearmament we are currently seeing will affect the environment through growing demand for materials, transportation, land use and the handling of defective ammunition. These environmental challenges can also be seen in Ukraine. We must try to better understand the extent to which war and military rearmament have long-term impacts on our environment. If we don’t, we risk failing to do enough to prevent war in the future,” concluded Ingulstad.

This article was first published in Aftenposten Historie Issue 2, 2026.