sentences:  His novel was followed by a non-fiction work, "U-Boot-Krieg" (U-Boat War) in 1976, which became the first part of a trilogy, together with "U-Boot-Fahrer" (U-Boat Sailors, 1985), and "Zu Tode Gesiegt" (Victory in the Face of Death, 1988).The trilogy includes over 5,000 photographs taken during World War II.He is also the author of the novels "Die Festung" (The Fortress, 1995), based on travels home across France in 1944, and "Der Abschied" (The Parting, 2000), about the nuclear-powered cargo vessel NS "Otto Hahn".