During the war, some merchant ships were converted into "auxiliary cruisers" and nine were used as commerce raiders sailing under false flags to avoid detection, and operated in all oceans with considerable effect. The German designation for the ships was 'Handelstörkreuzer' thus the HSK serial assigned. Each had as well an administrative label more commonly used, e.g. Schiff 16 = Atlantis, Schiff 41 = Kormoran, etc.