Diana Preston - Before the Fallout

Haukelid and his colleagues managed to discover that the Germans intended to transport the heavy water by rail from Vemork to the northern end of a long, narrow inland lake called Tinnsjo. Here, on Sunday, 20 February 1944, they would load the railcars onto the ferry sailing south down the lake to connect with the railhead at Tinnoset, whence the railcars with their cargo of heavy water would continue their journey to the coast for shipment to Germany. Three weeks before the shipment was due the Norwegians believed they had the answer. Haukelid radioed London that the most reliable solution would be to sink the ferry. Lake Tinnsjo was almost thirteen hundred feet deep, and it would be impossible for the Germans to retrieve the drums from its frigid depths.

They also warned London that “we must expect reprisals.” A special army detachment together with a company of S.S. had been called in to guard the shipment—a sign both of how seriously the Germans regarded the transport and of their likely response if thwarted. Indeed, the resistance were so worried about what the Germans might do to the civilian population that on 10 February they sent a further message, urgently querying whether the importance of the operation justified the potential consequences. London replied the same day. The answer was perhaps tactlessly breezy but also unequivocal: “Matter has been considered. It is thought very important that the heavy water shall be destroyed. Hope it can be done without too disastrous results. Send our best wishes for success in the work. Greetings.”

Haukelid reviewed the options again. Even putting thoughts of reprisals aside, the dangers to innocent passengers aboard the ferry were hard for him to stomach, but there seemed no choice. Disguised as a workman, he made a reconnaissance trip. He carefully timed how long the ferry took to reach the deepest part of the lake. The answer was twenty minutes. He knew that he and his fellow saboteurs would have to be very careful getting to the ferry and boarding it. The Germans were on high alert: “There were more Germans than Norwegians in the whole valley…. German police stopped everyone that looked suspicious and checked their identity cards and parcels they carried.” On another scouting mission, this time in Rjukan during a local music festival, Haukelid disguised himself as a musician, concealing his machine gun in a violin case like any Chicago gangster.

On the evening of 19 February, twelve hours before the ferry was due to depart, Haukelid and two companions, Rolf Sorlie and Knut Lier-Hansen, dodged through the shadows down to the landing where the ferry was moored for the night: “The bitterly cold night set everything creaking and crackling; the ice on the road snapped sharply as we went over it. When we came out on the bridge by the ferry station, there was as much noise as if a whole company was on the march.” While his comrades covered him, Hauke­lid, encumbered by a sack of explosives and detonators as well as his weapons, crept up the ferry gangplank. To his surprise, all seemed quiet apart from the voices of the crew playing poker belowdecks. The Germans had failed to place guards on the ferry—the most vulnerable link in the whole heavy water transport route.

Haukelid signaled to Sorlie and Lier-Hansen to follow him aboard. The trio crept below to the third-class accommodation and found a hatchway leading down to the bilges. However, before they could raise the steel hatch they heard footsteps and hastily took cover. It was the ferry watchman. According to Haukelid, they told him they were seeking a suitable place to hide. The man replied that he had several times helped conceal “illicit things” on the ferry and showed them the hatch. While Haukelid and Sorlie climbed down and got busily to work fixing the explosives, Lier-Hansen kept the watchman engaged in conversation.

“It was,” Haukelid later wrote, “an anxious job and it took time. The charge and the wire had to be connected; then the detonators had to be connected to the wire and the ignition mechanism. Everything had to be put together and properly laid. It was cramped and uncomfortable down there under the deck, and about a foot of water was standing in the bilge.” It was important that the ferry should sink quickly enough; Lake Tinnsjo was so narrow that unless the boat sank within five minutes, the captain might be able to beach her. Haukelid therefore laid the charge, consisting of nineteen pounds of sausage-shaped high explosive, toward the bows. On his reckoning, the blast would punch a hole about eleven feet square in the ship’s side, and the ferry would sink rapidly by the bows. The railway trucks holding the heavy water would roll off the deck and go to the bottom first. To be absolutely certain that the explosion occurred where the lake was deepest, Haukelid positioned two alarm clocks on a spar of the hull and wired them to the charge. He timed them to go off at 10:45 a.m. the next morning.

The saboteurs withdrew, telling the watchman that they had a few things to fetch and would be back on board in good time before the ferry sailed. Haukelid worried about the man who had been so cooperative and whom the Germans would be bound to interrogate after the ferry was sunk. The fate of two Norwegian guards at the Vemork heavy water plant, sent to Grini concentration camp after the February 1943 raid, still weighed on his conscience. Yet if they warned the watchman and he was absent when the ferry sailed, this would raise German suspicions. Haukelid contented himself with “shaking hands with the watchman and thanking him—which obviously puzzled him.”

As the three men ran from the ferry, they heard the rumble of the approaching train bringing the heavy water. Haukelid and Sorlie fled at once, Sorlie up into the mountains and Haukelid to catch a train the next day to Oslo and thence to ski to Sweden. Lier-Hansen was determined to remain behind to check that the ferry actually sailed. If there was any delay, he would defuse the bomb to prevent a premature explosion. The next morning on the train to Oslo Haukelid consulted his watch yet again. It showed 10:45. a.m. If all had gone according to plan, the ferry should now be sinking. A newspaper headline the next day—“Railway Ferry ‘Hydro’ Sunk in the Tinnsjo”—told him that the mission had, indeed, succeeded, though at a cost. Of the fifty-three people aboard, only twenty-seven survived. However, the canisters containing more than 1,300 pounds of heavy water lay beyond Nazi reach at the bottom of Lake Tinnsjo.

Despite an initial wave of arrests, the reprisals the Norwegian resistance had so feared did not materialize. General von Falkenhorst found it less embarrassing to maintain the fiction that the ferry’s boilers had exploded than to acknowledge another brilliant act of Allied sabotage and another example of German incompetence and carelessness.

THE ALLIES HOPED that they had significantly disrupted Germany’s bomb project. However, in the spring of 1944 their own experienced a crisis. One of the greatest scientific challenges was how to configure the bombs to ensure an explosion of the right force at the right time. Until then, the assumption had been that the two types of atomic weapon on which they were working concurrently—the uranium-fueled bomb, originally nicknamed “Thin Man” for Roosevelt but renamed “Little Boy” when the proposed gun barrel was shortened, and the plutonium bomb, nicknamed once and for all “Fat Man” for Churchill—would both be detonated by a high-velocity gun. This would fire one subcritical piece of fissile material into another, thereby creating a critical mass, initiating an uncontrolled chain reaction and producing the desired explosion. However, samples of plutonium produced by the Du Pont pilot plant at Oak Ridge, which began reaching Los Alamos at the rate of a gram a day from April 1944, showed an alarming capacity to fission spontaneously. The phenomenon was not entirely unexpected; the possibility of spontaneous fission had been raised in 1939 during discussions about how much material would be required to produce an atomic weapon. However, what worried the scientists was that these samples appeared five times more likely to fission spontaneously than plutonium hitherto produced for experimental purposes in cyclotrons. It was a rate never observed before.