This book is about the submarine war unleashed by Nazi Germany against the Western Allies and the USSR. It tells about the underwater forces of the German Navy, a lot of attention is paid to the "gray wolves" - submariners and the fate of "steel coffins" - submarines that have become a ruthless murder weapon. All the characters in the book are real faces, most of whom found their death on the ocean floor. The book publishes unique reference material about all German submarines of World War II.