“I’m here to find an SS officer,” I told the uniformed guard outside the Berlin Archives. “He saved my mother,” I added in German. The guard handed me a visitor pass and a white plastic bag emblazoned with the German coat of arms — a black eagle with red talons — and directed me to a red brick building across a parade ground where thousands of SS officers once lined up.I registered inside. I explained to a librarian that I knew the officer was of Ukrainian background, but I did not know his name. I had already contacted archives in...