During the eleventh and twelfth centuries, Norman expansion throughout Europe and the Mediterranean inspired the composition of historical texts and the production of cartularies. Norman writers attempted to explain the legitimacy of these conquests and the nature of Norman rule. The explosion of cartularies during the twelfth century attempted simultaneously to fortify old claims to land while expanding ownership to new territories. The most important sites of historical work in southern Italy were in the great monastic houses of the Monastery of Saint Benedict at Monte Cassino, Santa Sophia in Benevento, Sant’Angelo in Formis and San Vincenzo al Volturno, all of which were founded in the Lombard period (774–1076) or earlier and were extremely wealthy under the Lombard princes. For centuries these monastic houses had important connections to popes, emperors and princes from across Europe and the Mediterranean. All these houses faced new challenges in the Norman period, and they composed histories and cartularies in order to address the presence of the Normans in the region and the changing religious landscape. Central to these narratives and collections of documents were concerns about property and independence. These collections responded to serious legal threats and in doing so they explored the nature of political and religious authority within the region and the role that monastic houses played in building connections between outside powers and southern Italy.

Monte Cassino’s register was subtly different from the other collections, preserving not a record of the monastery or its abbots but instead the political landscape of southern Italy. The monastery of Saint Benedict, owing to its religious importance and geographical position, acted as a powerful political broker in the region, leading the community to amass hundreds of documents from Lombard princes, German emperors, Byzantine officials, regional Italian kings, Norman conquerors and popes. The validity of these documents and the cartulary more generally has been called into question because of the role of Peter the Deacon in its production. Peter the Deacon is widely considered to be one of the most brazen forgers in the Middle Ages, and scholars have been reluctant to use the register owing to questions surrounding the validity of documents. I argue that Peter the Deacon, because he was a forger, was keenly attuned to what gave documents power and to the mechanics of political rule in meridional Italy.