Assessing the Accuracy of U-Boat War Diaries: A Case Study of U-156's Fourth Patrol and World War II Navigation Techniques.

This article analyzes the accuracy of positional data recorded in the Kriegstagebücher (KTB), or war diaries, of German U-boats during World War II, focusing on U-156’s fourth patrol. It evaluates navigational methods used—celestial navigation, dead reckoning, and radio direction-finding—and compares 106 paired latitude-longitude coordinates with corresponding German naval grid squares, finding an 89.6% match within a 5-nautical-mile tolerance but only 55.7% exact matches. The study identifies errors stemming from recording mistakes and map-reading challenges under operational conditions, and notes discrepancies in reported meeting positions with other U-boats. The findings highlight the inherent limitations of World War II navigation technology and advise caution when using U-boat war diaries as precise historical location sources.