The Christianization of Scandinavia in the High Middle Ages is a central event in the historical experience of the societies living in northern Europe. It marked an important step in the integration of the Scandinavian territories into the dynamics of European history. Since the beginning of modern historiography, in the nineteenth century, the study of this phenomenon has been the subject of many studies. When dealing with the written evidence of what has sometimes been called the process of conversion but which we call the Christianization process, historians traditionally separated the sources into two major groups: those Scandinavian in origin, and those composed by “outsiders,” who observed or commented from a distance. Since both types of source tend to present narratives from quite different perspectives, modern historiography has also varied its interpretation of the historical experience according to the credibility attributed to the sources analyzed. Consequently, the Christianization process in northern Europe has given birth to many different narratives—both medieval and modern—concerning how it happened, most of which conflict with each other. Medieval chroniclers, Scandinavian saga writers, runestone carvers, modern antiquarians, historians, archaeologists, linguists: all have presented their different views on when and how Christianity was introduced and became dominant in northern Europe. Therefore, to some degree, modern interpretations have varied depending on whether their selected sources confirmed or opposed current tendencies and historiographical agendas. One of these sources is the Gesta Hammaburgensis ecclesiae Pontificum of Adam of Bremen, with which this book deals.

The Gesta Hammaburgensis is a historical narrative of the deeds of the archbishops of Hamburg–Bremen in the Early and High Middle Ages. It was composed by Adam, a magister scholarum, that is, an intellectual linked to the diocese of Hamburg–Bremen, in the middle of the eleventh century. Adam’s account is divided into four books, each of which deals with different epochs and circumstances regarding the archdiocese’s past and present. In the first book, the scholar narrates the events leading to the foundation of the diocese under the missionary bishop Ansgar, up to the episcopacy of Unni, who resumed missionary activity in Scandinavia at the beginning of the tenth century. The second book presents the deeds of the archbishops during the tenth and the beginning of the eleventh centuries.