This introduction opens with a story about a Jewish relief worker writing home. The reader is then introduced to the vast suffering of Jews in the Great War. Together, the war experience, American ascendancy, the Balfour Declaration, the Russian Revolution, the new states of East Central Europe, and new migration restrictions completely transformed Jewish life across Europe, the Middle East, and the Americas. The chapter then provides a European, American, and Jewish genealogy for the emergence of American Jewish humanitarianism prompted by the war. It summarizes the narrative arc of the book, chapter by chapter, from relief to the Eastern war zones during American neutrality, to postwar emergency relief with other American organizations, to the development of several thematic forms of long-term relief across East Central Europe, the Soviet Union, and the Eastern Mediterranean. Several characteristics of international Jewish humanitarianism in this era are explained, such as its grounding in American pluralism, welfare state Progressivism, and diaspora connections. This history is both a Jewish intervention into the field of humanitarianism history and a rethinking of the master narrative of humanitarianism via the Jews.