During the nineteenth century, Ashkenazi Jewish society in Europe underwent a radical transformation. Until this point, the Jews had constituted a religious-national minority, divided into local communities with more or less homogenous social and religious institutions. Now, large sectors of the Jewish public reorganized themselves into new social frameworks and divided into religious streams. The beginnings of this process can be seen already in the second half of the eighteenth century with the rise of Hasidism, but it was only during the next hundred years that the trend became more institutionalized and variegated. The main currents that crystallized included Reform, Orthodox and Conservative Judaism. Each current encompassed sub-groups which resulted from the various social and historical contexts in which these streams developed. The process included internal splits and competition as well as independent developments within each movement. Beginning in Germany at the start of the nineteenth century, the phenomenon spread to Bohemia, Hungary, England and the United States, reaching Eastern Europe toward the end of the century.

Whereas the Reform and Conservative movements have basked in the historiographical limelight for decades, Orthodoxy has received serious attention as a subject worthy of historical research only during the last twenty years. The late Prof. Jacob Katz defined the phenomenon and encouraged his students to investigate it. In his opinion, Jewish Orthodoxy emerged at the end of the eighteenth century as a response to the challenges of modernity in general, and to the other Jewish religious currents in particular. The strengthening of Orthodoxy in recent years has stimulated research into its historical roots.

Over the years, Orthodoxy itself evolved and became more diversified in its responses to the challenges presented by other Jewish religious trends (Reform and Positive-Historical Judaism in Germany, Neologism in Hungary) and Jewish social movements, especially in Eastern Europe (Zionism and Jewish Socialism). Zionism added a new aspect to the problem of modernity: the question of how to relate to Zionist activity in the Land of Israel and specifically whether to cooperate with “errant” Jews in this regard. In addition, Zionism invested messianic aspirations with new meaning. At the same time, Orthodoxy was essentially a reaction to the secularization of Jewish society, a subject which has not yet been sufficiently analysed and evaluated in historical research.