Christianity had, from its earliest days, an uneasy relationship with violence. Christ preached turning the other cheek to one’s enemy, but he also drove the moneychangers forcibly out of the Temple. While many Christians subscribed to a prescriptive condemnation of clerics who actively fought or engaged in military battles and campaigns, there were always clerics who ignored these prescripts and took on such roles, with greater or lesser relish depending on the cleric in question. This chapter surveys the most important texts, trends, and laws of the church as they pertained to military activity and the use of arms by clerics over the first thousand years of Christianity. The goal is to illuminate the creation of a set of prescriptive rules for the military behavior of clerics, with the tacit understanding that the reality of clerical behavior was far different. What will be shown is that, while military force by clerics was never openly accepted within the canonical tradition, there was much more ambivalence over it in the broader cultural discourse than has normally been considered. The debate over whether violence was licit for Christians, let alone clerics, was well under way in the period prior to the acceptance of Christianity by Constantine. After the adoption of Christianity by the Roman Empire, military activity by Christians had to become legitimated (though this did not necessarily have to extend to clerics). Early councils, in fact, legislated against the participation of clerics in warfare, though with the dissolution of Roman, and later Carolingian, power, clerics nevertheless took on a larger role in defending their regions and in carving out noble holdings, both of which often involved the use of military power.

The presumed ideals of the Christian church were, on the surface, antithetical to an embrace of violent warfare, thus the early arguments in the church were over whether Christians in general could be soldiers. Many modern historians portray the early church as uniformly pacifist, or nearly so, and that with the embrace of the religion by Constantine and the Roman government, accommodations had to be made by the religion regarding violence.