'Freshman' was a Free Norwegian special forces attack on the Vemork 'heavy water' (deuterium oxide) manufacturing facility in Norway (19/20 November 1942).

'Freshman' was the first of a series of undertakings by the Norwegian resistance movement to prevent the Germans from acquiring heavy water for use in their atomic research programmes, the other elements being 'Grouse' (i), 'Grouse' (ii) and 'Gunnerside'.

In 1934, the first industrial facility had been built at the Norsk Hydro plant at Vermork to produce fertiliser, and a by-product of this process was heavy water, of which 12 tons were created each year. During World War II, to prevent Germany from developing nuclear weapons, the Allies decided to destroy the heavy water plant by targeting the 60-MW hydro-electric plant at the Rjukan falls in Telemark.

Before the German invasion of Norway on 9 April 1940, the Deuxième Bureau (French military intelligence) had removed almost 410 lb (185 kg) of heavy water from what was then neutral Norway. The facility’s director had agreed to the transfer for the duration of the war. The capability for the production of more heavy water still remained, however, and the Germans began to exploit this fact. This caused considerable worry among the Allies, who therefore endeavoured to destroy or, at the very least, to disable the facility.

When Germany started to consider the possibility of building an atomic bomb it found that the most difficult problem to be overcome was how to obtain sufficient 'weapons grade' material, which comprised particular isotopes of uranium and plutonium. In order to produce these materials, which only uranium is found in nature, and then only in tiny quantities, it is necessary either to extract the uranium from natural ore or to 'breed' plutonium from uranium in a nuclear reactor. The German scientists decided to use plutonium as the critical mass required is smaller than that of uranium.

Unable to perfect a graphite-moderated reactor for plutonium production, the German scientists explored a design based on the use of heavy water. Such a reactor could have been used to undertake bomb research, and, ultimately, to breed the plutonium from which a bomb could have been manufactured.

The need to destroy the Norsk Hydro plant was agreed by President Franklin D. Roosevelt and Prime Minister Winston Churchill in 1942, and between 1942 and 1944 a sequence of sabotage actions by the Norwegian resistance movement, as well as Allied bombing, ensured the effective destruction of the plant and the loss of the heavy water which had been produced.

The initial attempt to destroy the Vemork facility, 'Freshman' was the first gliderborne operation conceived and executed in the UK, and was mounted by Admiral the Lord Louis Mountbatten’s Combined Operations Headquarters in November 1942. The plan consisted of two operations: the first would drop a number of Norwegian locals into the area as an advance force, and once this was ready a party of British engineers would be landed by glider to attack the plant itself.

On 19 October 1942 a four-man team of Free Norwegian special forces trained by the Special Operations Executive was parachuted into Norway. From their drop point in a remote area the men had to ski a long distance to the plant, so considerable time was allocated to the completion of this 'Grouse' part of the mission.

The next phase of the plan went ahead on 19 November, this 'Freshman' involving the gliderborne landing on the frozen Lake Møsvatn near the plant. But the 34 Royal Engineers of Major General F. A. M. Browning’s British 1^st Airborne Division, together with the crews of two Airspeed Horsa gliders and one Handley Page Halifax four-engined glider tug, died when their aircraft crashed into mountains as a result of poor visibility. The Norwegians were unable to reach the crash site before the Germans. Of the soldiers captured from the first glider, the four injured men were later poisoned by a German doctor under orders from the Gestapo, and on 18 January 1943 the five uninjured men were shot by the Gestapo agents in accordance with Adolf Hitler’s 'Commando Order' of 18 October 1942. The survivors of the second glider were executed within a few hours of their capture at the German barracks at Bekkebo, their bodies being stripped and thrown into an unmarked grave. Although the local Norwegian population could not prevent the prisoners being executed, they later recovered their remains and reinterred them in marked graves.

The Norwegian 'Grouse' team thereafter had a long and very hungry wait in their mountain hideaway. The British were aware of the continued existence of the 'Grouse' team and decided to undertake another operation with it. By this time the original 'Grouse' team had been redesignated as 'Swallow'. In February 1943 'Gunnerside' used another Halifax bomber, of No. 138 Squadron tasked with the support of special operations, to drop another six Norwegian commandos into Norway. This six-man team arrived successfully and linked up with the 'Swallow' team after a few days of searching. The combined team then made final preparations for their assault on the night of 27 February. After the failure of the 'Freshman' attempt, the Germans had set mines, floodlights and additional guards round the Vemork plant.

During the winter, however, the locally high state of readiness had declined significantly, although this did little to reduce the difficulty of reaching the plant, which required movement over a 80-yard (75-m) bridge spanning the deep ravine at whose bottom, 655 ft (200 m) below the bridge, ran the Man river. The attackers decided to climb down into the ravine, ford the river and then climb up the far side. The winter level of the water was very low and on the far side the men followed the single railway track straight into the facility without encountering any guards.

Even before 'Grouse' had landed in Norway, the SOE had placed in the facility a Norwegian agent who had supplied detailed plans and schedule information. The demolition party used this information to enter the main basement. No one interfered with the completion of the attack and the party’s escape: in order to persuade the German that this had been a British attack and not an undertaking by the local resistance forces, which would have resulted in reprisals against the local population, a British weapon was deliberately left at the site. All 10 men made good their escape, and while six of them skied 250 miles (400 km) to Sweden, the other four remained in Norway for further work with the resistance.

The damage to the plant had been repaired by April, however, and the SOE concluded that a repeat raid would be extremely hard to effect successfully as German security had been tightened and strengthened.

In November a daylight precision attack on the plant was undertaken by 143 Boeing B-17 Flying Fortress four-engined heavy bombers of the USAAF. The attackers dropped 711 bombs, of which at least 600 missed the plant. The damage caused by the others was quite extensive, and succeeded in halting production for a short time. Almost as soon as production resumed, the USAAF started a series of raids on the facility. The Germans were convinced that this would eventually result in some success, and therefore opted to abandon the plant and move remaining stocks and critical components to Germany in 1944.

Knut Haukelid learned of the plan and decided to sabotage the ferry carrying the railway tankers with the heavy water across Lake Tinnsjø. Haukelid slipped into the ship and planted a bomb, with 8.8 lb (4 kg) of explosives, on the keel of the ferry Hydro, after which he escaped. On 20 February, just after midnight, the ferry and its cargo sank in deep water shortly after sailing, effectively halting Germany’s atomic weapon development programme.

Unknown to the saboteurs, SOE had already prepared a back-up plan, designating a second team to attack the shipment at Herøya should the first attempt fail.

The disassembled factory was later found in southern Germany during the closing stages of the war by members of 'Alsos' nuclear seizure force.