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 vigilantly avoided detection by the occupying Germans.

The second effort would not fail. After parachuting to a plateau, the second group, some of whom grew up in the area, 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.