Assessing the Accuracy of U-Boat War Diaries: A Case Study of <i>U-156</i>’s Fourth Patrol and World War II Navigation Techniques

This study examines the accuracy of positional data recorded in the war diaries ( Kriegstagebücher or KTB) of German U-boats during World War II, with a focus on U-156’s fourth patrol. U-boat navigational methods, including celestial navigation, dead reckoning, and radio direction-finding, are analyzed to assess their precision. U-156’s KTB is scrutinized, comparing 106 recorded latitude and longitude coordinates with corresponding naval grid squares, revealing an 89.6 percent match rate within a 5-nautical-mile tolerance but only 55.7 percent within exact grid squares. The study identifies errors in the KTB due to recording inaccuracies and map reading challenges, exacerbated by operational conditions. Encounters with other U-boats and distress calls provide additional data points, confirming discrepancies. The findings underscore the inherent limitations of World War II navigational technology and suggest a need for caution when using these historical records for precise location verification. This analysis contributes to a nuanced understanding of maritime navigational accuracy during the war, highlighting both the strengths and pitfalls of U-boat war diaries as historical sources.