The peace testimony has the advantage of a very long history. There have been Christian pacifists throughout Christian history, but the same cannot be proven of Christian supporters of war. For the first three centuries of the church, the advice and the stories that come to us have been consistently against war. When advising people whether or not to enlist in the military, the advice was don’t. When we read of Roman soldiers becoming Christians, most often we read of these soldiers being executed for the crime of their Christianity.
The stories that the early church hand down to us are the stories of the church in conflict with the governments. Christians might have been non-violent, but the reason they were executed was for resisting the rule of the state. Christians pledged their allegiance to Christ — and would not pledge loyalty to Caesar. It is unthinkable to join the military of an enemy state — especially when it is forbidden to fight for the Kingdom where your loyalty lies. A Christian would not fight against the enemies of the Church, because the highest honor a Christian might have is to die a martyr, just as Christ did before.
As Christianity won the hearts and minds of the people, Rome began to change. In the 4th Century Constantine claimed Christianity and soldiers began to become baptized as Christians without being executed for treason. Christianity had to deal with a reality where they were no longer engaging in civil disobedience and nonviolent resistance against the government — they were now respected members of society.
This new position in society required Christian thinkers to ask questions that had never come up before. When Christians participated in ever level of society, and society was rapidly becoming Christianized — Christians had to adapt from the position that Rome was an enemy to the position that Rome was an ally. Clearly this adaptation did not include hiding the past, the stories of martyrs and opposition were still told and celebrated, but there were also new stories told of how Constantine changed Rome — and some of these new stories included soldiers fighting under the standard of Christ.
Constantine’s Rome puts Christianity in a condition where there is a spectrum of opinions on what the Christian’s role is in this world. This spectrum ranges from pacifism to the level that the person avoids any involvement with the government to having a religious nationalist militarism, seeing service to God being the same as military service to the nation. The stories told include both those who were killed by Roman soldiers — and those of Roman soldiers who fought under the Chi-Rho standard.
These competing narratives create a challenge for theologians — do the theologians give the Emperor the right to determine that something is moral in certain conditions that would be immoral under all other conditions? Do the theologians call for a return to the days when to be a Christian was to be in rebellion against the emperor — or do they seek something that is completely different.
Just War Theory is exactly that, and it is somewhat misnamed. Just war theory knows that war is evil — but it also has an element of pragmatism, recognizing that sometimes force is necessary to stop another evil. Just war theory traditionally had two sides to it. There were ethics for the person who decided that force should be used, and there were ethics for these who applied the force. Before declaring war, the government has to determine that the war is winnable, without causing more harm than the evil that it is warring against. For the person waging the just war — the rules are use as little force as possible, and don’t harm the innocents. Just war, as described, is police work at its best — it is never what we would actually call war.
Personally, I’m an advocate of the just war theory, because it calls on people at every level to be ethical. When people point out that we needed war to stop Hitler, we should realize that Hitler would not have gotten anywhere without a system of policemen who arrested falsely, judges who perverted justice while sentencing, and soldiers who never asked the question: “Is this the right thing to do?” Wherever the answers to address such evil lie, it is not maintaining the systems that enable evil. Ultimately, when people behave ethically at every level, the outcome will be peace.