I know my great-grandfather died at Gallipoli, but we can't find any records of him because nobody in the Ottoman Empire had surnames. How does a bureaucracy operate without surnames to simplify census taking and tax collecting?
hi! You might consider x-posting this to /r/geneaology: they'll have lots of experience using and navigating official records from various cultures. (And incidentally, there are still cultures that don't use surnames, so this isn't necessarily an issue of the past)