AUDIE CORNISH, HOST:
In 1943, a daring mission put the brakes on Nazi Germany's atomic weapons plans. Norwegian saboteurs pulled it off and with no casualties.
AILSA CHANG, HOST:
The last surviving member of that team died Sunday. Joachim Ronneberg was 99.
CORNISH: When British intelligence learned that a plant in Nazi-occupied Norway was making heavy water, a necessary ingredient for atomic weapons, they had to take action.
NEAL BASCOMB: The big question was how to attack this plant.
CORNISH: Neal Bascomb wrote a book on the raid called "The Winter Fortress: The Epic Mission To Sabotage Hitler's Atomic Bomb."
BASCOMB: It was in this sort of slot valley, which made it very difficult to bomb.
CHANG: An aerial assault was attempted and failed. So the British turned to Joachim Ronneberg and eight others. Team members dropped by parachute 40 miles from the target. They had to ski to the site in a blizzard. The plant was heavily guarded and reachable only, or so the Germans thought, over a narrow suspension bridge.
BASCOMB: There were minefields surrounding it. The single-lane suspension bridge was armed by two sets of guards 24 hours a day. So it was impenetrable.
CORNISH: Or so it seemed. Ronneberg and his team found a perilous way in.
BASCOMB: They decided that the only way to approach this plant was to climb this cliffside in the middle of night in the middle of winter - about a 500-foot cliff - that the Germans never thought that anyone would be able to mount.
CORNISH: They got in, planted explosives and destroyed the heavy water plant. The team escaped and skied 200 miles to Sweden. And Berlin's nuclear weapon quest was substantially slowed.
CHANG: As for Joachim Ronneberg - well, he had more missions in the war, but only when he learned of American atomic bombs dropped on Japan two years later did he fully understand what his mission had prevented. Author Neal Bascomb feels the young Norwegian saboteur deserves a lot of credit.
BASCOMB: Joachim Ronneberg had no military experience. He was 23 years old. He was put in charge of a team of all individuals who were not only older than him but had more experience than him. And yet he managed to assemble them into a team that was extraordinarily effective. And it was just a remarkable accomplishment.
CORNISH: On the 70th anniversary of the mission, Ronneberg spoke to the BBC.
(SOUNDBITE OF ARCHIVED RECORDING)
JOACHIM RONNEBERG: We were a gang of friends doing a job together. Somehow, we were lucky all the way. All the things we were afraid of came out to our benefit.
CHANG: All the things we were afraid of came out to our benefit. Joachim Ronneberg never had to chew the cyanide suicide pill he took on that mission. He enjoyed another 75 years of life hailed as a hero in Norway and died Sunday at age 99. Transcript provided by NPR, Copyright NPR.