Evacuation of Finnish signals intelligence establishment to Sweden, 1944
Operation Stella Polaris was the cover name for an operation in which Finnish signals intelligence records, equipment and personnel were transported to Sweden in late September 1944 after the end of combat on the Finnish-Soviet front in World War II. The purpose was to enable the signals intelligence activities against the advancing Russians to continue in Sweden and to prevent the equipment falling into the hands of the Soviet Union. A Soviet invasion was considered likely and plans were made to support guerrilla warfare in Finland after a possible occupation.
https://en.wikipedia.org/wiki/Operation_Stella_Polaris