The Arctic Circle defining the "midnight sun" encompasses the Atlantic Ocean from the northern edge of Iceland to the Bering Strait. The area is often considered part of the Battle of the Atlantic or the European Theatre of World War II. Pre-war navigation focused on fishing and the international ore trade from Narvik and Petsamo. Soviet settlements along the coast and rivers of the Barents Sea and Kara Sea relied upon summer coastal shipping for supplies from railheads at Arkhangelsk and Murmansk. The Soviet Union extended the Northern Sea Route past the Taymyr Peninsula to the Bering Strait in 1935.