Antisemitism emerged toward the end of the nineteenth century as a powerful political movement with broad popular appeal. It promoted a vision of the world in which a closely-knit tribe called “the Jews” conspired to dominate the globe through control of international finance at the highest levels of commerce and money lending in the towns and villages. This tribe at the same time maneuvered to destroy the very capitalist system it was said to control through its devotion to the cause of revolution. It is easy to draw a straight line from this turn-of-the-century paranoid thinking to the murderous delusions of twentieth-century fascism. Yet the line was not straight. Antisemitism as a political weapon did not stand unchallenged, even in Eastern Europe, where its consequences were particularly dire. In this region, Jewish leaders mobilized across national borders and in alliance with non-Jewish public figures on behalf of Jewish rights and in opposition to anti-Jewish violence. Antisemites were called to account and forced on the defensive. In Imperial and then Soviet Russia, in newly emerging Poland, and in aspiring Ukraine—notorious in the West as antisemitic hotbeds—antisemitism was sometimes a moral and political liability. These intriguing essays explore the reasons why, and they offer lessons from surprising places on how we can continue to fight antisemitism in our times.