NEW YORK — There was no Google Earth, no Gore-Tex, and only a modest measure of hope on the February night in 1943 when six Norwegians parachuted into the remote and frigid Telemark region of their home country for an outdoor challenge like few others.
They had skis and explosives and a destination: the German-controlled Norsk Hydro facility, high on an isolated and snowy ridge. The Norwegians intended to destroy equipment inside that the Germans were using to produce what is known as heavy water, a crucial ingredient in making a nuclear weapon and one they feared the Nazis would use to build an atomic bomb. One of the demolitions experts on the team, Birger Stromsheim, died Nov. 10 in Oslo at 101.
It was not the first attempt to destroy the heavy water equipment. Just a few months earlier another group of four Norwegians became stranded in the area after British soldiers for whom they were doing advance work were captured, tortured, and eventually killed. That first group hunkered down for the winter in an abandoned cabin, built a makeshift radio from a car battery and stolen fishing rods and began planning their own rescue and another assault on Norsk Hydro. They ate lichen that they scraped from rocks, killed an occasional reindeer for meat, and avoided detection by the occupying Germans.
The second effort did not fail. After parachuting to a plateau, the second group skied in subzero temperatures for several days before uniting with the four stranded soldiers. The combined group then made its way to the opposite side of a steep gorge from the Norsk Hydro facility. With the only bridge across guarded by Nazis, they descended to the bottom and climbed to the top on the other side.
Mr. Stromsheim was 31 at the time of the assault, the oldest member of the mission. He was particularly respected for his expertise in explosives and for his ability to stay calm.
‘We didn’t think about whether it was dangerous or not.’
‘‘We didn’t think about whether it was dangerous or not,’’ Joachim Ronneberg, the leader of the mission, recalled in an interview in The Telegraph of London in 2010.
A Norwegian caretaker, a civilian, was the only person in the room where the heavy water was produced, and he quickly agreed to cooperate. Ronneberg said that setting the dynamite proved to be easy, but the men still worried that they would be detected. They lighted a 30-second fuse and ran.
‘‘They didn’t reckon that they would get out alive,’’ Mr. Stromsheim’s son, also named Birger, recalled.
Stormy conditions helped muffle the explosion inside the building, and the men made it safely back across the gorge before the Germans realized what had happened. Many years later, experts determined that the Nazis were far from being able to build a nuclear weapon.
Mr. Stromsheim, who grew up skiing, hiking, and bicycling, was among several soldiers who made it to safety by skiing more than 200 miles to Sweden.
Birger Edvin Martin Stromsheim was born Oct. 11, 1911, in Alesund, Norway. His parents had a small farm. In addition to his son, he leaves a daughter, Liv Kristen Oygard; four grandchildren; and three great-grandchildren. His wife, Aase Liv, died in 1997.