On 18 October 1942, a party of Norwegian agents were dropped into Telemark, Norway, for Operation Grouse. They were part of a mission to sabotage the German nuclear weapons programme by disrupting the stockpiling of heavy water at Vemork Norsk Hydro chemical plant. Arthur Herman is on Warfare today to explore the stories of these brave Norwegians. Why were they best suited to the job? And do their actions reveal anything about the so called Viking hearts of Scandinavia?