This work takes a look at the formidable U-boat bases and bunkers built on the French coast (Brest, Lorient, St Nazaire, La Pallice, Bourdeaux), in Norway (Bergen, Trondheim), and Germany (Keil, Hamburg, Helgoland), and also focuses on the huge Valentin factory complex at Bremen, which manufactured the new type XXI electro-boats. Bunker protective systems, such as camouflage, light and heavy flak installations and nearby air cover are also covered.