Nazi-occupied Norway, February 27, 1943

In a staggered line, they cut across the mountain on their skis. Dressed in white camouflage suits over British Army uniforms, the young men threaded through the stands of pine and moved down the sharp, uneven ground. The silence was broken only by the swoosh of skis and the occasional slap of a pole against a branch. The warm, steady wind that blew through Vestfjord Valley dampened even these sounds. This was the same wind that would eventually, hopefully, blow their tracks away.

A mile into their trek, the woods became too dense and steep to descend by any means other than by foot. The nine Norwegian commandos took off their skis and balanced them on their shoulders. Then they slid and trudged down through the wet and heavy snow. They carried thirty-five-pound backpacks filled with survival gear, submachine guns, grenades, pistols, explosives, and knives. Each one also had a cyanide pill in case of capture by the enemy. Often the weight of their equipment made them sink to their waists in the snow.

Suddenly, the forest cleared, and they came upon the road. Ahead of them, on the other side of a terrifying gorge, stood Vemork, their target. The enormous power station, and the eight-story hydrogen plant in front of it, were built on a rocky shelf that extended over the gorge. Below it, the Måna River snaked through a valley so deep that the sun rarely reached its base. Despite the distance across the gorge, and the wind singing in their ears, the commandos could hear the station’s low hum.

Before Hitler invaded Norway and the Germans seized control of the plant, Vemork would have been lit up like a beacon. But now its windows were blacked out to discourage nighttime raids from Allied bombers. High on the icy crag, its dark silhouette looked like a winter fortress. A single-lane suspension bridge provided the only point of entry for workers and vehicles, and it was closely guarded by the Nazis. Mines littered the surrounding hillsides. Patrols swept the grounds. Searchlights, sirens, machine-gun nests, and a barrack of troops were also at the ready.

And now the commandos were going to break into it.

The young men stood mesmerized. They had been told the plant produced something called “heavy water,” and with this mysterious substance, the Nazis would be able “to blow up a good part of London.” But none of the saboteurs were there for heavy water, or for London. They had seen their country invaded by the Germans, their friends killed and humiliated, their families starved, their rights curtailed. They were there for Norway, for the freedom of its lands and people from Nazi rule.

They refastened their skis and started down the road to their mission.