Having read the book 'Operation Hannibal' by M. Eggleston and F. Rogers describing this operation, which being well written, there was however only detailed mentioning of the land war and German naval organized surface efforts. These already being well documented due to the appalling loss of life. I recalled the subject being looked at back, way back as it turned out to November 2008 where only a few U-boats involved were listed. However of the sites recommended for reference, two provided larger numbers of U-boats, which listed between 49 and 52 plus UD4, these undertook 61 and 66 evacuations, of which sadly two U-boats were lost [U923 and U3520. Lately with more time free due to lock down I decided to look further into this operation and identified more boats, taking the total up to 66 + UD4 confirmed as carrying 'passengers' in over 92 sailings between them.
However during this I listed another 108 boats with 132 sailings during the same period [Jan - Apr], yet none are listed as if they carried anyone besides the crews. This seems highly unlikely with other boats sailing same days from the same ports laden with military and refugees onboard. I appreciate record keeping at this time was chaotic, but is any research being undertaken on this impressive undertaking by the U-boats? John