The Winter Fortress

How the Nazis were stopped from obtaining "heavy water", an ingredient key in making an atomic bomb.
01 June 2016




The Winter Fortress charts an epic scientific adventure and spy story about the greatest act of sabotage in all of World War II. Here is an excerpt from the opening of the book, chronicling the heroic efforts to destroy Nazi access to deuterium oxide--"heavy water"--an essential ingredient in their plans to build a weapon that could decide the war.

On February 14, 1940, Jacques Allier, a middle-aged, nattily dressed banker, hurried through the doors of the Hotel Majestic, on rue la Perouse. Situated near the Arc de Triomphe, the landmark hotel had welcomed everyone from diplomats attending the Versailles peace talks in 1919 to the influx of artists who made the City of Light famous in the decade that followed. Now, with all of France braced for a German invasion, likely to begin with a thrust through Belgium, and Paris largely evacuated, a shell of its former self, conversation at the hotel was once again all about war. Allier crossed the lobby. He was not there on bank business but rather as an agent of the Deuxieme Bureau, the French internal spy agency. Raoul Dautry, the minister of armaments, and physicist Frederic Joliot-Curie were waiting for him, and their discussion involved the waging of a very different kind of war.

Joliot-Curie, who with his wife, Irene, had won the Nobel Prize for the discovery that stable elements could be made radioactive by artificial or induced methods, explained to Allier that he was now in the middle of constructing a machine to exploit the energy release when atoms split (or fission). Most likely this machine would serve to power submarines, but it had the potential for developing an unsurpassed explosive. He needed Allier's help. It was the same pitch Joliot-Curie had given Dautry months before, one made all the more forceful by the suggestion that the energy held within an ordinary kitchen table, if unlocked, could turn the world into a ball of fire. Allier offered to do whatever he could to help the scientist.

pipesJoliot-Curie explained that he needed a special ingredient for his experiments -- heavy water. While most hydrogen atoms consist of a single electron orbiting a single proton in the atom's nucleus, there was a variant, or isotope, of hydrogen that carried a neutron in its nucleus as well. He called this isotope deuterium, or heavy hydrogen, because its atomic weight (the sum of an atom's protons and neutrons) was 2 instead of 1. The isotope was extremely rare in nature (.015 percent of all hydrogen), and there was just one molecule of heavy water (D2O) for every 41 million molecules of ordinary water (H2O). What made heavy water so important, Joliot-Curie explained, was its rare ability to help foster an atomic chain reaction.

The physicist continued that there was only one company in the world that produced heavy water to any quantity: Norsk Hydro, in Norway. As an official at the Banque de Paris et des Pays-Bas, which owned a majority stake in the Norwegian concern, Allier was ideally positioned to obtain whatever supplies Norsk Hydro had at its Vemork plant as quickly and discreetly as possible. The French prime minister himself, Edouard Daladier, had already signed off on the mission.

There was one problem, Allier said. Only a month before, the chief lawyer for Norsk Hydro, Bjarne Eriksen, had visited him in his Paris office. According to Eriksen, the Germans were also interested in the production at Vemork. They had placed a number of orders and had suggested that they might need as much as two tons of heavy water in the near future. Startled by the demand for such vast quantities -- and denied any information about how the material might be used -- Norsk Hydro had yet to fulfill more than twenty-five kilograms of these orders.

This report troubled Dautry and Joliot-Curie deeply. The Germans must be on the same track with their atomic research. Allier needed to move -- and fast -- to secure the stock before the Germans did. If there was trouble in bringing it out of Norway, he was to see that the heavy water was contaminated, thus rendered useless for experiments.

Two weeks later, Allier headed across the vast hall of Paris's Gare du Nord and boarded a train to Amsterdam. He was traveling under his mother's maiden name, Freiss. Concealed in his briefcase were two documents. One was a letter of credit for up to 1.5 million kroner for the heavy water. The other gave him the authority to recruit any French agents required in smuggling out the supply. Short of the false beard, Allier felt like he had all the accouterments of a hero in the spy novels he loved.

From Amsterdam he flew to Malmo, Sweden, then took a train to Stockholm. There he sat down with three French intelligence agents, tasking them to meet him in Oslo a few days later. Early on March 4, Allier traveled by train to the Norwegian capital, arriving into Eastern Central Station. At the French Legation, he learned that his cover was already blown. An intercepted message from Berlin's spy agency, the Abwehr, had been deciphered. "At any price," it read, "stop a suspect Frenchman traveling under the name of Freiss."

Allier was undeterred. He left the legation and rang Norsk Hydro from a public phone booth. Within the hour, he entered the company headquarters at Solligata 7, a short distance from the royal residence of King Haakon VII. In a meeting with Dr. Axel Aubert, Allier made his offer to buy the company's stocks of heavy water. He said nothing about their intended use, unsure that he could trust Aubert. The tough, long-standing director general, who looked like he chewed stones for breakfast, was clear: his sympathies were with France; he had refused the Germans any great quantities of heavy water, and he would provide Allier with whatever he needed.

VermokThe next day, Allier traveled by car to Vemork, one hundred miles west from the Norwegian capital. Aubert followed. Their arrival at the plant, a fortress of concrete and steel set at the edge of a steep icebound precipice, was unannounced. Inside, Aubert led the meeting with Vemork's lead engineer, Jomar Brun. Allier was simply introduced as an official with Banque de Paris. From previously unsold supplies and the restart of production, the plant had a total of 185 kilograms at hand. All of it, Aubert told Brun, needed to be transported secretly to Oslo by truck. Brun asked to know why, just as he had asked why when Aubert had quietly told him earlier in the year to explore a fivefold increase in production to 50 kilograms a month. As before, Aubert declined to answer any questions and instructed that not a word of this special order was to be mentioned to anyone.

After settling these arrangements and finding a Rjukan welder to make twenty-six stainless-steel flasks that would fit neatly into suitcases, Allier returned to Oslo with Aubert to conclude their negotiations and prepare for spiriting the flasks out of Norway. The Norsk Hydro director general offered to give France the heavy water on loan, with no price attached, and told Allier that Norsk Hydro would provide France with first claim on what was produced in the future. Impressed by this generosity -- and the alacrity with which Aubert had moved -- Allier opened up about the intended use of the heavy water by Frederic Joliot-Curie and his team.

On March 9, two trucks departed Vemork down the road. Brun rode in the first truck. At a nondescript house in Oslo, they unloaded the twenty-six flasks and entrusted them to Allier's care. The house was owned by the French government and was a stone's throw from an Abwehr safe house, but sometimes it was best to hide in plain sight.

To smuggle out the supply, Allier had grand visions of a submarine sneaking into Oslofjord and spiriting it away, but instead he settled for the old "bait and switch," supported by the three French spies he had recruited in Stockholm. Through several ticket agents and under various assumed names, they booked flights on two planes leaving Oslo's Fornebu airport at roughly the same time on the morning of March 12. One was headed to Amsterdam, the other to Perth, in Scotland. In case anything went wrong, they also bought seats on the same flights for two consecutive days after that.

At dawn on March 12, a frigid and cloudless morning, Allier and a fellow spy, Fernand Mosse, took a taxi three miles south of the city center to Fornebu. Dressed as businessmen, they made a big show of their upcoming trip to Amsterdam in front of the gate agents and baggage handlers who took their several large, heavy suitcases. Soon enough, they were crossing the tarmac toward the Junkers Ju-52 aircraft designated for their flight. Adjacent to their plane was an identical one, destined for Perth.

Once they were sure their baggage was loaded onto the Amsterdam-bound plane and its propellers began to spin, they readied to board. At that moment, a taxi drove onto the tarmac. Its passenger, Jehan Knall-Demars, another of Allier's team, had pleaded with the gate agent to let him through in the taxi so he could make his plane to Amsterdam. The spy had the taxi park between the two Junkers, out of view of the Fornebu terminal. From the trunk, he unloaded several suitcases, together containing thirteen of the heavy-water flasks. These were hauled into the baggage hold of the Scottish-bound plane, which Allier and Mosse boarded, instead of the one to Amsterdam. Knall-Demars left in the taxi, hiding in the back as he passed through the gate.

Minutes later, the plane to Amsterdam barreled down the runway and lifted into the sky. As it headed south over the Skagerrak, the strait of sea between Norway and Denmark, a pair of Luftwaffe fighters drew alongside. They ordered its pilots to divert their course to Hamburg. When the plane landed in Germany, Abwehr agents busted open the cargo hold. Rummaging through the suitcases, they found a few that were particularly heavy. Inside them? Granite rubble.

Meanwhile, Allier and Mosse landed safely in Scotland with their stash. The following day, Knall-Demars arrived with the other thirteen flasks.

By March 18, all twenty-six flasks were stored in the old stone-arched cellars of the de France in Paris. The first battle of heavy water was won. The next, however, was all too shortly to begin when the Germans invaded Norway and took control of Vemork straightaway. Ultimately, it would take a brilliant Norwegian scientist and a band of British-trained commandos to win the war of heavy water.


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