Gerbert d’Aurillac, later Pope Sylvester II, reigned as pope for only four years, from 999 until 1003, but he represents not only an excellent example of how the papacy sought to maximize its authority, but also how it viewed the role of warfare. Gerbert’s life, career, and political activities, in fact, demonstrate a good baseline of acceptable clerical behavior vis-a-vis warfare for the start of our period of study, at least from the perspective of a man well connected to papal politics. Gerbert was a scholar, an abbot, an archbishop, and eventually a pope. His actions were dictated by a sense of political expediency and are demonstrative of the importance of political pragmatism in determining licit behavior among the higher clergy. Gerbert was fully immersed in the secular affairs of his region and period, and his letters give us insight into the value of warfare to the clergy. What emerges, in brief, is that clergy (including Gerbert) could be comfortable taking on leading military roles in those violent times. This should not be surprising as we have already seen efforts and exhortations of some of the clerical reformers directed against just such behavior. Through the use of his letters, written either in his own name or on behalf of others such as Archbishop Adalbero, we see that Gerbert not only tailored his responses based on what was likely to best serve him politically, but that he also utilized violence and military action to achieve his political goals and those of his allies and friends.

Major clerics, including Gerbert himself, played leading roles in the warfare raging in France and Germany during this period. Between 985 and 990, many of Gerbert’s letters are concerned with the incessant warfare between Lothair of France, Hugh Capet, Otto of Germany, as well as numerous other lords, such as Count Godfrey of Verdun and Duke Thierry of Upper Lorraine, and many prelates, including Adalbero, bishop-elect of Verdun (and son of Count Godfrey) and Adalbero, archbishop of Metz (and brother to Duke Thierry). The clerics in particular were seen as vital to the wars, as Gerbert addressed letters specifically to them, including one in which he exhorted bishop-elect Adalbero, in the name of his father, to ‘guard all strongholds from the enemy’ and manfully to resist the Franks wherever he could.