U-boat is the anglicised version of the German word U-Boot, a shortening of Unterseeboot, literally "undersea boat". While the German term refers to any submarine, the English one refers specifically to military submarines operated by Germany, particularly in the First and Second World Wars. 

During World War II, U-boat warfare was the major component of the Battle of the Atlantic, which lasted the duration of the war. Germany had the largest submarine fleet in World War II, since the Treaty of Versailles had limited the surface navy of Germany to six battleships, six cruisers, and 12 destroyers but nothing on undersea boats. Prime Minister Winston Churchill wrote "The only thing that really frightened me during the war was the U-boat peril."

On April 6, 1945, a German navy submarine named the U-1206 departed from the port city of Kristiansand, in Nazi-occupied Norway, and began its first combat patrol with it’s captain Karl-Adolf Schlitt. Assigned to the waters of the North Atlantic, its mission was to seek out and destroy British and American ships on the high seas. (MORE ON THE PODCAST)