There is no denying that the early Catholic Church grew up in a climate predominated by a rich and broad religious pantheon. Emerging at first as a perceived outgrowth of Judaism, Christianity was exposed to, among other things, Roman culture. Roman religious practice, which was typically very open to adopting foreign cults, felt threatened by Christianity, resulting in periods of persecution. As a result, the early Christian community had a very complicated relationship with Imperial Rome. The Church stressed non-collaboration, but evidence points that there was a divide between teachings and practice on the topic of military service. The patristic writings of the Early Church fathers are noticeably sparse until Ambrose and Augustine, who present what can generally be called a theory of just war. They also waver between support and condemnation, reflecting the needs of their congregations.
Despite this relative absence of discussion, the prevailing attitude in the historical scholarship of the Early Church was that the pre-Constantine Church pushed for non-collaboration with Roman society, i.e. not serving in public office or the army. After Constantine, that same scholarship points towards an about-face in Church teachings, and a co-opting of the burgeoning Christian community. What this paper seeks to address is that Roman iustum bellum, and Christian just war, were developments specific to their contemporary societies and, while there is definitely a link, the two form distinct systems of thought. One might even say that iustum bellum was more concerned with justifying war, than the moral quandaries of Christian just war.