It was not just torpedoes that required regular attention and maintenance. With frequent submergence, there was a strong risk of corrosion and malfunction of the 8.8cm deck cannon. Thick coats of grease were applied whenever necessary. Here Bootsmaat Karl-Ernst Thiel and Reinhard Suhren, who began his U-boat career as an artillery officer, are working on the weapon’s starboard sighting mechanism. The delicate sight itself was detachable, and was usually removed prior to diving.

Photo & Caption featured in U-Boat War Patrol: The Hidden Photographic Diary of U564 by Lawrence Patterson