—the  Alderney concentration camps —and named them after the  Frisian Islands :  Lager Norderney ,  Lager Borkum ,  Lager Sylt  and  Lager Helgoland . The  Nazi   Organisation Todt  operated each subcamp and used forced labour  to build  bunkers , gun emplacements, air-raid shelters, and concrete fortifications. The Alderney concentration camps