World War II Day by Day

Vemork/Rjukan, German-Occupied Norway • February 27, 1943

Following Germany’s invasion of Norway in April 1940, German autho­rities took con­trol of Norsk Hydro’s Vemork hydro­elec­trical and chemi­cal facil­ity just outs­ide Rjukan in Tele­mark County. Vemork lay 100 miles/­161 km west of Oslo, Nor­way’s capi­tal. Although orig­i­nally designed to zap descending moun­tain water with an elec­tric cur­rent (elec­trol­y­sis) to pro­duce ammo­nia for nitro­gen fer­ti­li­zer, Vemork had recently become the world’s first indus­trial-scale pro­duc­tion site of “heavy water,” or deu­te­rium oxide (D₂O). (Heavy water refers to water con­taining a large pro­por­tion of deu­te­rium oxide com­pared with ordi­nary water.) The plant was set up to pro­duce many hun­dreds of kilo­grams of heavy water per year. Indeed, by May 1942 Vemork was pro­ducing 286 lb/­130 kg of heavy water a month. German scien­tists, unlike their Amer­i­can contem­po­raries who were also involved in nuclear wea­pons research, had decided to use heavy water as a “moder­a­tor” in their nuclear reactor, not the more readily avail­able graphite with which the Amer­i­cans were experi­menting. (A moder­a­tor slows down the bom­bard­ment of neu­trons and the fis­sion pro­cess [i.e., the split­ting of atoms], which releases huge amounts of energy.)

Now none of this physics talk ever reached the ears of the nine Nor­we­gian com­man­dos who infil­tra­ted the Vemork plant on this date, the evening of Febru­ary 27, 1943. They were neither told by their British SOE (Spe­cial Oper­a­tions Exe­cu­tive) handlers what the Germans intended to do with all the thou­sands of kilo­grams of heavy water they suddenly needed nor told what effect their covert oper­a­tion, if suc­cess­ful, might have on the out­come of the war. What the com­man­dos knew for cer­tain was that Oper­a­tion Gunner­side, their planned sabo­tage of the crit­i­cal water cells in the plant base­ment where the heavy water was manu­fac­tured, followed on the heels of two earlier SOE-spon­sored covert oper­a­tions. A recon­nais­sance team of four Norse soldiers (Oper­a­tion Grouse/­Swallow, October–Novem­ber 1942) was air­dropped to pre­pare the way for an attack on the plant by a party of 30 British com­man­dos, whose mili­tary gliders crash-landed miles short of their tar­geted landing site (Oper­­ation Fresh­man, Novem­ber 19, 1942). Twenty-three men who sur­vived the crashes were tortured and killed by the Gestapo (German Secret State Police).

Given the urgency to put the Fresh­man fiasco in the past, the British dropped six Gunner­side para­chu­tists into Norway on Febru­ary 17, 1943. Metic­u­lous planning, addi­tional details of the plant lay­out, and good luck were the rea­sons given by the Gunner­side com­man­dos for the suc­cess of their covert mis­sion. Ten days after inser­tion, now rein­forced by three Swal­low scouts, a nine-mem­ber sabo­tage squad led by Lt. Joachim Rønne­berg reached the Vemork plant with­out being detected by German and Nor­we­gian guards. Four men from the five-man demo­li­tion squad, also directed by Rønne­berg, daisy-changed deto­na­tor cords and charges next to the deli­cate base­ment machin­ery and lit the 30‑second fuses before making a clean get­away. The pyro­tech­nics were lethal: all 18 4‑ft‑tall/­1.2‑m‑tall ultra­fil­tra­tion cells were blown apart, their con­tents, mixed with the plant’s over­head cooling water, running into floor drains. Seeking revenge, 12,000 enemy troops swept the Vemork area, to no avail. After skiing more than 200 miles/­322 km, the Gunner­side crew reached safety in neutral Sweden, then England, where they were joined by the Swallow quartet.

The Gunnerside raid cost the Germans 350 kg (770 lb) of pure heavy water. The plant was decom­mis­sioned for a few months. But the spec­tac­u­lar suc­cess of the covert oper­a­tion was trumped by one of the Gunner­side’s own raiders, Knut Hau­lelid. Instead of returning to England, the Brooklyn native recruited a team of Nor­we­gian sabo­teurs to sink a ferry one week short of Gunner­side’s first anni­ver­sary. Nine­teen pounds/­8.6 kg of plastic explo­sive secreted in the bow of the SF Hydro, which was carrying semi-finished heavy water from the Vemork plant to research cen­ters in Germany, delivered the last barrels of the pre­cious stuff to the bottom of Lake Tinn (see photo essay below).

Norwegian Commandos Sabotage Germany’s Atomic Weapons Program

Left: Norsk Hydro’s Vemork hydroelectric plant near Rjukan, Norway, in 1935. At Rjukan a large water­fall was har­nessed to pro­duce chemi­cals related to the pro­duc­tion of artifi­cial ferti­lizer, including am­monia, potas­sium nitrate, heavy water (deu­terium oxide), and hydro­gen. In 1925 the plant part­nered with Germany’s IG Farben and later with Britain’s Imperial Chemi­cal Indus­tries (ICI). Starting in Decem­ber 1934, the Vemork plant was the only facil­ity in Europe that mass-pro­duced high con­cen­tra­tions of heavy water (a by­product of nitro­gen fixing) in the eight-story granite electrolysis building shown in the fore­ground of this photo­graph. The heavy­-water plant was closed in 1971. Today the origi­nal power plant is an indus­trial museum. One of its exhibi­tions covers the five sabo­tage opera­tions con­ducted by the Nor­we­gian resis­tance move­ment, British com­man­dos, and U.S. bombers between 1942 and 1944 to destroy the plant’s capa­city to aid the Nazis’ atomic bomb pro­gram, which depended on extremely scarce heavy water as a “moder­ator” in achieving a suc­cess­ful nuclear chain reaction. The Nor­we­gian Broad­casting Com­pany produced a six‑part mini­series, Kampen om tungtvannet (The Heavy Water War), about the SOE-trained sabo­teurs. The mini­series broke the record for the most highly viewed tele­vision drama in Norway. A 5‑minute trailer with English subtitles can be viewed on YouTube by clicking here.

Right: The twin-stack steam-powered railway ferry SF Hydro oper­ated on Lake Tinn (Tinnsjå, Tinnsjø). The 19‑mile‑long ferry trip made it pos­sible for Norsk Hydro to trans­port its chemi­cals from the Vemork plant at Rjukan to the coastal port at Skien. On Febru­ary 20, 1944, the ferry was blown up by the Nor­we­gian resis­tance move­ment at Lake Tinn’s deepest point (1,411 ft) with a load of semi-finished heavy water on­board, which was headed to Nazi Germany for what appeared to be a last-gasp use in that coun­try’s nuclear wea­pons pro­gram. (The Nazis had decided to abandon Vemork, their only source of heavy water, after the U.S. bombing of the facil­ity on Novem­ber 16, 1943.) The Lake Tinn book­end to Oper­a­tion Gunner­side deprived Adolf Hitler’s Third Reich of any chance, if there ever was one, of pro­ducing an atomic bomb. After the war it was con­firmed that the Germans were not even close to making an atomic bomb as the Allies had feared through­out the war. In his memoirs Nazi Minis­ter of Arma­ments and War Pro­duc­tion Albert Speer (pro­nounced “spare”) wrote: “On the sugges­tion of nuclear physi­cists we scuttled the pro­ject to develop an atom bomb by the autumn of 1942” because, as he said else­where “the tech­ni­cal pre­req­ui­sites for pro­duc­tion would take years to develop.” German war­time resources were thus allo­cated to other prior­i­ties. The wreck of the ferry and its inval­u­able con­tents were dis­covered in 1993. Sadly the sinking of the SF Hydro resulted in 4 German and 14 Nor­we­gian casual­ties. A largely fic­tional Holly­wood account of the sabo­tage, The Heroes of Tele­mark (1965), starred Richard Harris as Knut Haukelid, second in com­mand of Oper­a­tion Gunner­side. The film is prob­a­bly the best-known cine­matic repre­sen­ta­tion of one of the most heroic sabotage acts of World War II.

History of Norway-Based Efforts to Sabotage German Nuclear Weapons Program