The Channel Islands were the only part of the British Commonwealth occupied by Nazi Germany. The Germans built four camps, two of which later became Neuengamme subcamps on Alderney Island. The Alderney camps were named after the Frisian Islands: Lager Norderney, Lager Borkum, Lager Sylt and Lager Helgoland. The Nazi Organisation Todt (OT) operated each subcamp and used forced labourers to build bunkers, gun emplacements, air-raid shelters, and concrete fortifications. The Alderney camps had a total inmate population of about 6,000.