High Quality Content by WIKIPEDIA articles! German U-boat bases in occupied Norway existed between 1940 and 1945, when the German Navy, the Kriegsmarine, converted several naval bases in Norway into Submarine bases. Norwegian coastal cities became available to the German Navy after the invasion of Denmark and Norway in April 1940. Following the conclusion of the Norwegian Campaign, the occupying German forces began to transfer U-boats stationed in Germany to many Norwegian port cities such as Bergen, Narvik, Trondheim, Hammerfest and Kirkenes. Initial planning for many U-boat bunkers began in late 1940 and starting in 1941, the Todt Organisation began the construction of bunkers in Bergen and Trondheim. These bunkers were completed between 1942 and 1943.