During the occupation, several of the nation's naval ports were turned into U-boat bases that were used to harass Allied shipping in the North Atlantic and Arctic Oceans. These included Bergen, Narvik, Trondheim, Hammerfest and Kirkenes. Over 240 U-boats were stationed in Norway at various times during the war, most of them were members of the 11th U-boat Flotilla which had 190 U-boats in its fleet during the flotilla's career.