You are now listening to World War 2 Stories. I'm your host Steve Matthews. Today, I'll take you into the heart of one of the most consequential covert operations of the entire war - a mission so audacious and against such impossible odds that it reads like fiction. Yet every word of this story is true.

February 1943. While battles rage across Europe and the Pacific, a small group of Norwegian commandos are about to embark on a mission that might determine whether Hitler acquires the most devastating weapon ever conceived: the atomic bomb.

Their target: the Vemork heavy water plant, nestled in a nearly impenetrable mountain fortress in Nazi-occupied Norway. Their odds of success: virtually none. Their margin for error: absolutely zero. This is Operation Gunnerside - the remarkable sabotage mission that may have changed the course of history itself.