The raid on Vemork

Shortly before noon on 16 November 1943, American heavy bombers appeared over the valley of the Måna river in Telemark, Norway. Their target was the Vemork hydroelectric power station and the adjoining hydrogen plant owned by Norsk Hydro – the only place in the world where heavy water, which German physicists needed to build a nuclear reactor, was produced on an industrial scale. According to the most frequently cited figures, between about 140 and more than 160 aircraft of the Eighth Air Force reached the target and dropped more than 700 bombs. The power station was badly damaged, but the heavy water installation in the basement survived. More than twenty Norwegian civilians were killed, among them women and children, and the Norwegian government in London, which no one had warned of the raid, protested to the Allies. Even so, the attack achieved its purpose: the Germans decided to abandon production at Vemork and ship what remained to the Reich.

Heavy water after Gunnerside

On the night of 27–28 February 1943 Norwegian commandos in Operation Gunnerside blew up the electrolysis cells at Vemork and destroyed the stock of heavy water. The Germans, who had controlled the plant since the invasion of Norway in April 1940, quickly rebuilt it, however. The country was then ruled by the German Reich Commissioner Josef Terboven and, formally from 1942, also by the collaborationist government of Vidkun Quisling. According to most sources the installation was working again from April, and by the summer of 1943 it had regained full capacity. For Germany, whose research programme – the Uranverein – had staked everything on a reactor moderated by heavy water, Vemork was the only realistic source of the substance.

The Allies knew from Norwegian intelligence that production had resumed. In London and Washington it was still unclear how far the German physicists had progressed, and the fear that Hitler might be the first to obtain an atomic weapon drove both the Manhattan Project and the attacks on Vemork. General Leslie Groves, head of the American atomic programme, pressed for the plant to be destroyed. Since another sabotage operation seemed too difficult – after Gunnerside the Germans had greatly strengthened the plant’s guard – it was decided to use air power.

The Norwegians working with the British Special Operations Executive (SOE) objected to this solution. Professor Leif Tronstad, a chemist who before the war had helped set up heavy water production at Vemork and who in London was the mastermind of the operations against the plant, warned that the installation in the factory basement was protected by thick concrete, that bombs would not reach it, and that local people would be killed instead. His objections did not prevail.

The raid of 16 November

The raid on Norway was a major operation by the American strategic air forces, which since the summer of 1943 had been attacking targets in Europe ever more boldly and paying a high price for it – as over Schweinfurt on Black Thursday a month earlier. According to some accounts, almost 400 B-17 Flying Fortresses and B-24 Liberators took off from English airfields that day. Roughly half were bound for Vemork; the rest were to attack Kjeller airfield near Oslo and the Knaben molybdenum mine in the south of the country, which mattered to the German armaments industry. The flights lasted 9–10 hours; for some bomb groups they were the longest missions in their history to date.

The attack on Vemork was timed for the lunch break, when the fewest workers were expected to be in the plant. The first bombs fell at around 11.40 a.m. Sources differ on the number of aircraft: Norwegian studies most often speak of 143 B-17s dropping 711 bombs, while others state that about 160 B-17s and B-24s attacked Vemork and that a dozen or so Liberators which had lost their way bombed the nitrate factory in Rjukan itself instead. The figure of “160 bombers” therefore lies within the range given by historians. Accuracy was poor: wind, smoke and cloud meant that, by Norwegian estimates, at least 600 of the more than 700 bombs fell outside the plant, and no more than a dozen or so struck its buildings.

Those hits were enough to cause serious damage to the power station: the penstocks carrying water to the turbines were severed, the suspension bridge was destroyed, the generators were damaged and the upper floors of the hydrogen plant were reduced to rubble. Just as Tronstad had predicted, however, the high-concentration installation in the basement, where the heavy water was made, suffered no serious damage. The nitrate factory in Rjukan, which produced fertiliser, was on the other hand heavily damaged.

The victims

The most tragic consequence of the raid fell on the local population. One bomb scored a direct hit on a newly built air-raid shelter at Vemork. According to accounts gathered by historians, sixteen people died in it – most of them women, as well as children. Further victims were claimed by the bombing of Rjukan and of nearby houses. Sources put the total number of Norwegians killed at 21 or 22; several homes were also destroyed.

The government of Johan Nygaardsvold, in exile in London, learned of the raid after the fact. The operation had not been agreed with it, even though it concerned a target on Norwegian territory and carried an obvious risk to civilians. The Norwegians protested, and the affair grew into a serious diplomatic dispute with the Allies. The destruction of the factory in Rjukan caused particular outrage, since according to the Norwegians it produced mainly fertiliser for Norwegian agriculture and was of no significance to the German war effort. The dispute touched on a wider question: how to bomb industrial targets in an occupied, allied country without killing its citizens – the same problem that accompanied Allied raids on France, Belgium and the Netherlands.

The German decision

Although the heavy water installation itself had survived, the raid destroyed what it depended on – the supply of electricity from the power station. The Germans also concluded that the plant would henceforth be the target of regular air attacks and that defending so remote a site was impossible. They therefore decided to abandon heavy water production at Vemork, dismantle the most important equipment and ship the accumulated stock to the Reich – several hundred kilograms of solution of varying, mostly low, concentration.

For the Norwegian resistance this meant a new task. On orders from London, Knut Haukelid, one of the Gunnerside team who had stayed in the area, prepared an attack on the shipment. On the night of 19–20 February 1944 an explosive charge planted in the hull of the railway ferry Hydro sank her in the deep waters of Lake Tinnsjå, together with the barrels of heavy water. Fourteen Norwegians, passengers among them, and four Germans were killed. This operation, together with Gunnerside and the raid of 16 November, makes up what is known as the heavy water sabotage campaign.

Place in the war

The raid on Vemork was one of the few occasions on which the race for the atomic bomb took the form of open military action. In hindsight its military significance is debatable. After the war it emerged that the German atomic programme had been very far from building a bomb – as early as 1942 Albert Speer had judged it a long-term undertaking, and German physicists never managed to achieve a self-sustaining chain reaction before the war ended. According to Norwegian historians, even uninterrupted supplies from Vemork would have changed little. The Allies, however, could not be certain. British physicists had concluded by the summer of 1943 that the German work posed no immediate threat, but the intelligence picture was unclear, and the Americans – Groves above all – were unwilling to take the risk.

The people of Vemork and Rjukan paid for that uncertainty. The dispute with the Norwegian government also exposed the limits of a bombing strategy in occupied countries: bombs dropped from several kilometres up into a narrow valley killed civilians and failed to hit the target itself. Sabotage – Gunnerside and the sinking of the Hydro – achieved more at the cost of far fewer lives. In the end the Germans never obtained enough heavy water from Norway to build a working reactor, and the first atomic bomb was built by the Americans in 1945.