During the first months of the First Crusade, groups of crusaders attacked the Jewish communities in the Rhineland, forcing them to choose between death and conversion. Many converted, but others chose to die as martyrs. Among these, some were killed by the crusaders, some killed themselves, each other, or even their own children in order to prevent forcible conversion. These events are described in a number of Latin accounts, but also in three Hebrew chronicles and in a number of Hebrew liturgical poems. These Hebrew chronicles introduce many new ideas connected to martyrdom which are not found in earlier Jewish martyr texts. They also differ considerably from contemporary texts on martyrdom, written by Jews living under Muslim rule. The purpose of the present study is as follows: to outline the most salient features of this new ideology of martyrdom found in the Hebrew Crusade Chronicles and how it differs from earlier Jewish tradition; to try to trace the roots of these new ideas, both by showing how the Chroniclers develop earlier Jewish ideas and also how they borrow notions and concepts from their Christian surroundings; to show what rhetorical means the Chroniclers use in order to present these innovations as firmly anchored in tradition; to attempt to explain why this ideology develops at this particular time and place, and thereby contribute some further methodological reflections on the nature of religious change, especially in a situation of persecution and oppression; to challenge the old paradigm that the Ashkenazic Jewish communities lived in isolation from their non-Jewish surroundings, and to suggest that a serious study of any medieval Jewish text must take into consideration the culture and current notions of the non-Jewish community in which the text was composed.