Drawing on the variety of archival sources in the host of European and Oriental languages, the book focuses on the history, ethnography, and convoluted ethnic identity of the Polish-Lithuanian Karaites. The vanishing community of the Karaites, a non-Talmudic Turkic-speaking Jewish minority that had been living in Eastern Europe since the late Middle Ages, developed a unique ethnographic culture and religious tradition. The book offers the first comprehensive study of the dramatic history of the Polish-Lithuanian Karaite community in the twentieth century. Especially important is the analysis of the dejudaization (or Turkicization) of the community that saved the Karaites from horrors of the Holocaust.