'Carolus' was the German clandestine use of special force elements of Hauptmann Dr Theodor von Hippel’s Bau-Lehr-Bataillon 'Brandenburg' zbV 800, the men wearing civilian clothes and posing as tourists, in central Norway and the island groups off that country’s west coast to secure bridges and other river crossings, clear the approach roads of mines, and block the border crossings with Sweden within the context of 'Weserübung' (5/12 April 1940).