The Heroes of Telemark

The Heroes of Telemark is a British 1965 Eastman Color war film directed by Anthony Mann based on the true story of the Norwegian heavy water sabotage during World War II. It was filmed on location in Norway.

Kirk Douglas plays Rolf Pedersen, a Norwegian physics professor, who, though originally content to wait out the war, is soon pulled into the struggle by local resistance leader Knut Straud based on Knut Haukelid, portrayed by Richard Harris.They are both smuggled to Britain to have microfilmed plans of the hydroelectric plant examined, and then return to Norway to plan a commando raid. When a force of Royal Engineers, who were to carry it out, are all killed, Pedersen and Straud lead a small force of saboteurs into the plant. The raid is successful, but the Germans quickly repair the equipment. ........

Source: Wikipedia