Missionaries are people who operate on the border between their own community and another. The confessional frontier between the Christian and the Jewish communities in Prussia offers a privileged vantage-point from which to analyze the relationship between them. This study makes comprehensive use of the archives and publications of the various Prussian institutions and societies which set out to convert Jews to Christianity. Spanning over two centuries of Protestant missionary activity, this book examines the ways in which theological, social, and racial themes intertwined in the relationship between the Christian majority in Prussia and the Jewish minority in its midst. This study sheds light on a facet of Jewish-German history which has been overshadowed by the ultimate tragedy of the Holocaust.