Operation Gunnerside was a covert mission carried out by the Norwegian resistance during World War II. Its primary objective was to sabotage the German nuclear weapon project by targeting the heavy water production facility at Vemork, Norway. The operation took place in February 1943 and involved a small team of commandos who successfully infiltrated the facility. The mission was significant because heavy water was crucial for the Germans in their efforts to develop atomic weapons. The commandos managed to destroy the facility's production capabilities, delaying the German nuclear program and contributing to the overall Allied war effort.