This was a British clandestine operation by the Special Operations Executive with the object of halting the flow of Swedish ferro-chrome to German-occupied Norway for shipment to Germany (17/18 April 1941).
The SOE department in neutral Sweden recruited a team of eight Swedes, who were collected from the coast in a Norwegian fishing vessel and transported to the UK for training before being delivered to Norway for 'Barbara'. Two three-man teams remained in Norway, the other two men being returned to the UK. On the night of 17/18 April one of the teams attacked the rail line linking Storlien and Trondheim, but managed to damage only one carriage. The two teams then made their way back to Sweden, where they were later arrested.