accelerated in the next few weeks.
The memorandum goes on to criticize the handling of production “entirely by large companies” — the Hungarian threnody Szilard and Wigner also sounded — and to propose a crash program directed by Urey and Fermi to build heavy-water piles. Nothing seems to have come of the Bethe-Teller proposal — Hitler's secret weapons proved to be the V-l and V-2 rockets then in development at Peenemunde, the first of which crossed the English coast on June 13, 1944 — but it captures the mid-war mood.
Less worrisome was radioactive dusting. Conant's subcommittee considered the possibilities and concluded that they were “rather remote.” Conant emphasized that he thought it
It was easier for Americans guarded by the wide moat of the Atlantic than for the British to dismiss the possibility of radioactive attack. Sir John Anderson, Chancellor of the Exchequer, a scientist and the member of Churchill's cabinet responsible for the Tube Alloys program, discussed the question with Conant at lunch at the Cosmos Club in Washington in August 1943. He was concerned particularly about German heavy-water production because British scientists believed they had found a way to separate light from heavy water at five times the efficiency of existing processes and feared their German counterparts might have made the same discovery. Heavy water would certainly work to moderate a chain-reacting pile. And such a machine might be used to breed radioactive isotopes for dusting London.
The British therefore kept closer watch on the High Concentration Plant at Vemork in Norway. It had not been damaged beyond repair. To the contrary, intelligence sources reported that summer, it had begun production again in April; German scientists had shipped heavy water from laboratory stocks in Germany to refill the various cells and speed restoration of the cascade.
When Niels Bohr escaped from Stockholm to Scotland on October 6, 1943, he carried with him Werner Heisenberg's drawing of an experimental heavy-water reactor. Bohr met more than once in London that autumn with Sir John Anderson; Anderson matched up Bohr's information with the Conant subcommittee's radioactive- warfare study and the Norwegian underground's news of Vemork's renewed production and concluded that the plant once again urgently required attack. The Nazis had significantly increased security at Vemork, which ruled out another commando raid. After British and American representatives discussed the problem in Washington George Marshall authorized precision bombing.
American Eighth Air Force B-17's climbed northeast from British bases before dawn on the morning of November 16. To minimize Norwegian casualties the aircraft were scheduled to drop their bombs during the Norsk Hydro lunch period, between 11:30 a.m. and noon. No German fighters came up from the defensive airfields of western Norway to delay them and they elected to circle over the North Sea to kill time before penetrating the Scandinavian peninsula. That alerted German flak, which took a limited toll as the bombers crossed the coast. One hundred forty got through to Vemork and released more than seven hundred 500-pound bombs. None hit the aiming point but four destroyed the power station and two damaged the electrolysis unit that supplied hydrogen to the High Concentration Plant, effectively shutting it down.
Abraham Esau of the Reich Research Council decided then to rebuild in Germany. To expedite construction the council planned to dismantle the Vemork plant and remove it to the Reich. The Norwegian underground reported that decision to London. Anderson was less concerned with the plant itself — Germany had only limited hydroelectricity to divert to its operation — than with the heavy water preserved in its cascade. British intelligence asked the Norwegians to keep watch.
Word came by way of clandestine shortwave radio from the Rjukan area on February 9, 1944, that the heavy water would be transported under guard to Germany within a week or two — not enough warning to prepare and drop in a squad of saboteurs. Knut Haukelid, who had spent the past year living on the land and organizing future military operations, was the only trained commando in the area except for the radio operator. He would have to destroy the heavy water alone with whatever amateur help he could assemble.
Haukelid slipped into Rjukan at night and met secretly with the new chief engineer at Vemork, Alf Larsen. Larsen agreed to help and they discussed possible operations. The heavy water, of enrichments varying from 97.6 down to 1.1 percent, would be transferred to some thirty-nine drums labeled potash-lye. “A one-man attack on Vemork,” writes Haukelid, “I considered out of the question… The only practical possibility, therefore, was to try to carry out an attack on the transport in one way or another.” He and Larsen, joined later by the Vemork transport engineer, considered the various stages of the journey. The drums of water would go by train from Rjukan to the head of Lake Tinnsjo. From there the cars would be run onto a rail ferry to travel the length of the lake, proceeding beyond Tinnsjo again by train to the port where they would be loaded aboard a ship bound for Germany. Blowing up the trains would be difficult and bloody, since they would be crowded with Norwegian passengers; Haukelid finally decided to attempt to sink the ferry, which also carried passengers, into the 1,300-foot lake. The transport engineer agreed to arrange to dispatch the heavy water on a Sunday morning, when the ferry was usually least crowded.
Sabotaging the boat would almost certainly mean the deaths of some of the shipment's German guards, which would call down heavy reprisals in the Tinnsjo area against the Norwegian population. Haukelid radioed London for permission, emphasizing that his engineer compatriots had questioned if the results were worth the reprisals:
The fact that the Germans were using heavy water for atomic experiments, and that an atomic explosion might possibly be brought about, was a thing we now talked of openly. At Rjukan they doubted very much whether the Germans had come in sight of a solution. They also doubted whether an explosion of the kind could be brought about at all.
The British begged to differ:
The answer came from London the same day:
“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.”
So Knut Haukelid laid his plans. He put on workman's clothes, packed his Sten gun into a violin case, identified which ferry would make the run on Sunday, February 20, 1944, the appointed day, and rode it with one eye on his watch. The
Months earlier the British had dropped supplies to the Norwegian commando that included sticks of plastic explosive. Haukelid strung the stubby sticks together to make a circumferential loop to cut a hole in the bottom of the ferry. “As the Tinnsjo is narrow, the ferry must sink in less than five minutes, or else it would be possible to beach her. I… spent many hours sitting and calculating how large the hole must be for the ferry to sink quickly enough.” To test his timing mechanism he hooked up a few spare detonators at his cabin on the mountain above Rjukan after a long night's work, set the alarm for evening and lay down to sleep. The detonators went off on schedule; he bolted bewildered from bed, grabbed the nearest gun and reflexively covered the door. “The timing apparatus seemed to be working properly.”
On Saturday Haukelid and a local compatriot, Rolf Sortie, slipped into Rjukan. It was crowded with German soldiers and SS police. An hour before midnight “Rolf and I went over to the bridge which crossed the river Maan and had a look at our target.” The freight cars “had been run up under some lamps, and were guarded… The train was to go at eight next morning, and the ferry was due to leave… at ten.”
