The Norwegian heavy water sabotage was a group of Allied missions in World War II. The target of the missions was the 60 megawatt Vemork power station. This power station produced a type of water that is named heavy water. Heavy water is based on a hydrogen isotope called deuterium. The missions were to stop Germany from making heavy water. Germany needed the heavy water to understand and help make an atomic bombs. The attacks started in February 1942 by Norwegian Commandos and Allied bombers. The missions were code named Grouse, Freshman, and Gunnerside. The missions were successful and the Vemork power plant was no longer working by 1943.