Over the nearly fifty years since his death in 1970, Herbert Grundmann’s formative influence on the field of medieval religious history has become increasingly evident. Renowned for his innovative and scrupulous research into the beliefs, ideas, practices and processes that shaped religious worlds from the twelfth to the sixteenth centuries, Grundmann revealed entirely new vistas of the medieval past. Generations of scholars have since approached their research from vantage points shaped by his arguments, whether those points of view were attained via personal contact, by reading his many publications or inherited through doctoral work and other secondary scholarship. Central to this gradually widening circle of influence were his German students, whom he mentored up until his death.

By the last decades of the twentieth century, this secular, source-based and cultural-historical approach had rippled through French, Italian, British and other European scholarship, producing in its wake research on a wide range of topics: monasticism, education, literacy, universities, theology, apostolic life, women's religious communities and expression, heresy and inquisition, popular or lay religious life, apocalyptic thought and prophecy and so on. American scholars inspired by Grundmann's methods soon generated their own studies of the medieval religious landscape, in turn introducing their own doctoral students to the ‘Grundmann’sche’ model. That Grundmann opened his door to foreign graduate students both at home and at the Monumenta Germaniae Historica suggests awareness of, and perhaps a sense of kinship with, these far-flung circles of medieval scholarship.

By the time of this publication, Grundmann's influence has been incorporated, whether consciously or not, into the research of hundreds of medievalists around the globe. Yet, for those without skill in reading German, the precise and subtle distinctions of Grundmann's arguments have been largely inaccessible. The 1995 English translation of his masterwork Religiose Bewegungen into Religious Movements of the Middle Ages was an invaluable contribution to that audience and generated new waves of engagement with Grundmann's complex and wide-ranging theses.