While historians of Christianity have generally acknowledged some degree of Germanic influence in the development of early medieval Christianity, Russell goes further, arguing for a fundamental Germanic transformation of Christianity. This first full-scale treatment of the subject follows a truly interdisciplinary approach, applying to the early medieval period a sociohistorical method similar to that which has already proven fruitful in explicating the history of Early Christianity and Late Antiquity. The encounter of the Germanic peoples with Christianity is studied from within the larger context of the encounter of a predominantly "world-accepting" Indo-European folk-religiosity with predominantly "world-rejecting" religious movements. While the first part of the book develops a general model of religious transformation for such encounters, the second part applies this model to the Germano-Christian scenario. Russell shows how a Christian missionary policy of temporary accommodation inadvertently contributed to a reciprocal Germanization of Christianity. Applying insights from the behavioral sciences and Indo-European studies to analyze this pivotal transformation of the West, this book will interest students and scholars of religion, history, sociology, and social psychology, as well as those who wish to further their understanding of the history of Christianity and of Western civilization.