If Just War Theory is the definition of what is minimally acceptable (which is the point), then we should take seriously when the ancient saints and fathers spoke emphatically that military service was, in fact, in opposition to the Christian way. St. Martin of Tours, for example, when he was being pressed into military service emphatically said that, as a soldier of Christ he was not permitted to fight. St. Marcellus of Tangiers cast off his military belt in front of the emperor, which ultimately gave him his martyr's crown. St. Hippolytus in his Apostolic Traditions writes that a catechumen/baptismal candidate who does not cast aside his military belt and oath is to be rejected.
The fathers are not mild in their opposition to war and violence, they are exceptionally clear. Just War Theory did not exist until Christians started having political power as magistrates and emperors. Which is why St. Augustine, for example, bothered at all to try to craft a Just War Theory. Just War Theory is, itself, a compromise. There was no such thing as a Just War Theory for the fathers who lived before the Edict of Toleration. Just War Theory is a response and reaction to a brand new event in the history of the Church: Christians in positions of political power, Christianity as the favored, and later official religion of the Empire.
And there is valid, patristic, reason to challenge that co-mingling of Church and State that was forged, ultimately, under Theodosius I. After all, it doesn't take a genius to see that the collusion of Church and State was a miserable failure. Whether we are talking Byzantine or Western political power. The Church has always been most faithful when she is not in charge of the world, but when she is suffering in it. And this can be seen throughout history, whether we are talking the Holy Martyrs of Nagasaki, the precious saints who came through the Diocletian persecution, or both Protestant and Catholic martyrs in the post-Reformation era.
Embracing the State as anything more than a public necessity for the organization of human civilization has consistently resulted in the compromise of the Christian faith. Crusades, pogroms, the holocaust, it is all the collaborative guilt of us, as Christ's people in the world. Our failure to be faithful disciples. Such things should drive us to our knees in repentance. It's why St. Pope John Paul II actively devoted himself to a ministry of reconciliation and repentance. That's what it means to fear God. Which Christians in the modern era have forgotten. Especially in their love of political power.
-CryptoLutheran