There are six criteria that must be satisfied before entering war can be considered just:1. Just Cause-- There must be a just and proper reason for going to war. Some of the justifiable reasons include self-defense, protecting the innocent (e.g., preventing genocide), restoring human rights wrongly denied, and assisting an ally in their self-defense.2. Proportionate Cause-- The good of going to war must outweigh the destruction and death that will be caused by warfare. In other words, going to war must prevent more evil and suffering than it is expected to cause.3. Right Intention-- Our reasons and motives for engaging in warfare must noble and in line with the ethic of Christian love. We can go to war to right a wrong or restore a just peace but not to restore our "national pride" or to seek revenge against an enemy.4. Right Authority-- War can only be authorized by a legitimate governing authority. This means it has to be a governing authority we would recognize as fitting the criteria of Romans 13. But it also means that the proper governing authority has actual sovereign authorization to engage in war. For example, the President of the United States has the proper authority to initiate warfare against Canada while the governor of North Dakota does not.5. Reasonable Chance of Success-- The initiation of warfare brings violence, pain, and suffering. This cost is only worth paying if it will, as we noted, outweigh the destruction and death that will be caused by warfare. If there is no reasonable chance of success in warfare there can be no reasonable chance of using warfare to restore a just peace.6. Last Resort-- Engaging in warfare must be the last reasonable and workable option for addressing problems. Any peaceful alternatives, such as diplomacy or non-violent political pressure, must first be exhausted before going to war.Historically, Christian thinkers have proposed two primary criteria for just execution of war, discrimination and proportionality.Discrimination-- The criterion of discrimination includes two key components, "innocence" and "deliberate attack." The first rule of just warfare is that we do not target or kill the innocent. In this context, the term innocence refers to whether individuals are able cause direct harm-- whether willingly or reluctantly-- either to us or to our military forces that are engaged in just warfare. Such people are considered "noncombatants" and are immune from attack because the meet the qualification of innocence.Proportionality-- The criterion of proportionality in waging warfare is similar to the criterion of “proportionate cause” in deciding to go to war: The good of going to war must outweigh the destruction and death that will be caused by warfare. In other words, going to war must prevent more evil and suffering than it is expected to cause.
It is not the purpose of this post to get into the details of these criteria. The crucial point to be made is that in the history of the church, the burden of proof has rested on those who would wage war, not on those who oppose it. Specific criteria need to be met in order to go to war, and then once the war is being fought, it must be fought in certain ways. Any war that does not meet the criteria of the first question is unjust if war is declared, and any war is unjust if it is fought without regard to the criteria of the second question. These criteria are so important that theoretically once war is being waged, if one side realizes it cannot win the war without fighting it unjustly, the only recourse is surrender. In other words, those who embrace some aspect of the JWT theoretically are situational pacifists. If the criteria are not met, there should be no war. In other words, for pacifists and just warriors nonviolence is the default position.
I cannot speak for war in other religious traditions-- Muslims, Jews, Hindus, and others will have to speak for themselves. But what I can say is that throughout church history, the default position for Christians has always been one of nonviolence. That is the church's natural state. Peace is the normal condition.
Sadly, that has not always been so. Indeed, it seems that for much of the church in America, nonviolence is not the default position. Even from a superficial glance of the church in American history, it appears that the burden of proof no longer rests with those who are beating the drums of war, but those who are opposed. In the lead up to the War in Iraq that began in 2003, it was obvious that those who urged caution were the ones that had to explain themselves. Churches throughout America almost immediately after the drums started to beat, threw themselves into patriotic worship and casting the soon-to-be conflict in terms of holy war. Christians who objected were accused of being unpatriotic and called all manner of disparaging names by other Christians! Pope John Paul II rightly came out in opposition to the war because it did not satisfy the criteria of the JWT (the official position of the Catholic Church) to the consternation of many Catholics in America.
For many Christians today, a just war means nothing more than a war we want to fight, and fight in any way necessary to win. There is no longer any consideration that in order to stay away from noncombatants, we must be willing to sacrifice more of our combatants, not because we want to, but because to target those unarmed would be unjust. No longer is surrender an option if the war cannot be fought justly. We must win at all costs even if more harm is done in winning the war as opposed to suing for peace. Is it possible to imagine during the Gulf War, President George W. Bush going on national television to say," I have consulted with our generals and we have come to the conclusion that we cannot win this war and fight it justly. Therefore, I have sent a communique to Saddam Hussein asking him for terms of peace." Of course, that would never happen, but for those who say they take just war seriously, that truly is an option. Nonviolence is the default position.