Hi John

It often depends on the source of the data used by the different authors to compile the list of U-boat patrols. The movements were recorded in the BdU/FdU and Flotilla KTBs and it was easier to collect the data from these sources than to do this with the KTBs of all U-boats. However, it also made it difficult to distinguish the sailings between war patrols, aborted patrols, trials or transfers. Moreover the number of war patrols made by certain U-boats sometimes differ even in original documents (for example when U-boats on transfer were redirected to defensive patrols en route or it is difficult to define when a "patrol" began and ended for U-boats on escort duty in home waters).

Generally we chain sailings if a patrol was aborted and continued after a few days, the same is done if U-boats made a stopover in Norway or other forward bases to refuel and resupply before continuing to their patrol area. To analyze and correct the patrol data for such occurrences is a time consuming process that hasn't a high priority, but I correct them whenever I come across one.

Best regards
Rainer

Crew member of uboat.net