High Quality Content by WIKIPEDIA articles! The Shetland Bus was the nickname of a clandestine special operations group that made a permanent link between Shetland, Scotland, and German-occupied Norway from 1941 until the German occupation ended on 8 May 1945. From mid-1942 the official name of the group was "Norwegian Naval Independent Unit" (NNIU). In October 1943 it became an official part of the Royal Norwegian Navy, and was renamed the "Royal Norwegian Naval Special Unit" (RNNSU). The unit was operated initially by a large number of small fishing boats, and later augmented by three fast and well-armed submarine chasers ? Vigra, Hessa and Hitra. Crossings were mostly made during the winter under the cover of darkness. This meant that the crews and passengers had to endure very heavy North Sea conditions, with no lights, and constant risk of discovery by German aircraft or patrol boats. There was also the possibility of being captured whilst carrying out the mission on the Norwegian coast.