How open-source naval information circulated during war

A German officer reportedly objected that the annual had recorded his U-boat as sunk. Books sold through neutral countries such as Switzerland could circulate beyond their country of publication and into enemy hands. The surrounding report compares German Schnellboote with British motor gun boats and motor torpedo boats, notes their fighting in the Channel and North Sea, and records that German surface raiders had become less prominent during 1942. The error and response expose the uncertainty of wartime loss lists and the reach of commercially published naval information. Openly published technical and operational details could become part of an international feedback loop.