The film begins with old footage in World War II with a narrator explaining that Germany produced hundreds of U-boats to control the Atlantic. In 1942, groups of U-boats known as "wolfpacks" sink over 1,000 Allied ships. The Germans began winning the war and if they continue destroying the Allies, Europe will fall. In 1943, Franklin D. Roosevelt and Winston Churchill declared that stopping the U-boats was their main priority. With new technology and the United States committed to the war, the Allies begin destroying the U-boats, bringing a rapid end to the wolfpacks.