The Nazis never got close to building the bomb, but they understood the science and knew what was coming. A top-secret raid led by Norwegian resistance fighter Roachim Ronneberg destroyed a heavy water-producing plant in Rjukan, Telemark in 1943, was a key event that put Nazi nuke research to bed. Ronneberg died this week at 99.
The following year, Ronneberg chose a team of five other commandos in an Allied operation codenamed Gunnerside.
"We were a gang of friends doing a job together," he told the BBC during the 70th anniversary of the mission.
The men parachuted on to a plateau, skied across country, descended into a ravine and crossed an icy river before using the railway line to get into the plant and set their explosives.
"We very often thought that this was a one way trip," he said.
After the explosion, the men escaped into neighbouring Sweden by skiing 320km (200 miles) across Telemark - despite being chased by some 3,000 German soldiers.
With a wry smile, Ronneberg described it as "the best skiing weekend I ever had".
The Nazis had no real hope of getting nukes: they'd effectively purged academia of physicists years earlier, and many who remained were drafted to the army in non-research roles. When reading elaborate counterfactual histories concerning different outcomes to World War II, remember that in all of them Germany gets nukes for Christmas in 1945.
Ronneberg told a BBC interviewer that he only realised the importance of the mission after the bomb on Hiroshima.
