When Is a War Just?

Most Christians agree that it is sometimes right for Christians to serve in the military. This consensus is based on the fact that the New Testament declares the legitimacy of government, the necessity of its use of force against evil (Romans 13:3-4; 1 Peter 2:13-14), and the responsibility of Christians to cooperate with the legitimate power of government (Matthew 8:5-9; Luke 3:14; 6:15; 14:31; Acts 10-11).

During the church’s first 300 years, very few Christians served in the military. The obvious reason for their reluctance to serve was that the Roman government was corrupt, and the military was often used to persecute their own fellow believers. The questions of the degree to which Christians should support war, or the standards by which they should determine whether any particular war is just or unjust only became major issues after the conversion of Constantine and his endorsement of Christianity as the empire’s dominant religion. Following the Edict of Milan (ad 313), Christians began to share in the power of government, and the church’s association with political power soon brought corruption. Rather than continuing to view the teachings of Jesus Christ as their ethical model, many Christians began to look to the Old Testament for analogies that falsely identified Rome with Israel and viewed its wars against pagan enemies as a continuation of Israel’s wars against the Canaanites.

Thoughtful Christians like the influential Augustine of Hippo stood against such rationalizations and declared: “War should be waged reluctantly and with tears in one’s eyes.” Following Augustine,1 the church fathers carefully developed a set of standards for a “just war” based on biblical principles. Here is a summary of these principles:2

Just War Principles

War cannot be just unless all nonviolent options have been tried and have failed.

Just war can only be waged by legitimate authorities, not private individuals and groups.

Just war can be waged only in response to an injury suffered (e.g., an enemy attack) with the motivation of appropriate compensation for the wrong suffered. (In other words, an aggressive war of conquest is by definition unjust.)

War can be just only if there is a reasonable degree of likelihood of victory. To shed blood in unwinnable conflicts is never just.

A war can be considered just only when the peace it seeks to establish will be better than the peace that already exists.

A war is just only when violence committed against the enemy is proportional to the violence suffered at the enemy’s hands. Excessive force is never just.

Just wars never target civilians. The deaths of civilians in a just war must be the unavoidable consequence of attacks on military targets.

Just war principles have always been violated in war. Soldiers caught up in the emotions of battle and hatred of the enemy have murdered, pillaged, and raped. However, Christian just war principles at least tempered the effects of war in the West until modern times.

Tragically, with the rise of secular national states, “just war” theory was swept aside on a massive scale, first in Europe during the Napoleonic conquests, and then in North America during the Civil War. The scale of national violence continued to mount through the 20th century, and Christians have become accustomed to participation in wars that have little concern for justice, proportionality, and safety of civilian populations.

The writer of the epistle of James stated:

What causes wars, and what causes fighting among you? Is it not your passions that are at war in your members? You desire and do not have; so you kill. And you covet and cannot obtain; so you fight and wage war. You do not have, because you do not ask. You ask and do not receive, because you ask wrongly, to spend it on your passions. Unfaithful creatures! Do you not know that friendship with the world is enmity with God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God (4:1-4).

Christians must guard against allowing earlier Christian collaboration with unjust war to serve as a precedent for their own support of unwarranted violence. Great wars have always involved the tragically flawed decisions of men who turned away from peaceful options, and the violations of just war principles that occurred in these wars always set the stage for further escalation of evil.

It is tempting for Christian citizens of powerful nations to shrug their shoulders and say: “Times have changed. Modern weapons and terrorism have made the principles of just war untenable.” Tragically, many evangelicals have become so accustomed to “total war” that they assume any war their government initiates is necessary.

As we exit a century that has been savaged by human violence and atrocity on a scale far greater than anything the world had seen before3 and enter a new century with even more potential for conflict and destruction, it is high time that evangelical Christians repent their blind nationalism and worship of Caesar and return to their calling as peacemakers (Matthew 5:9; Philippians 2:15; James 3:17-18).

Genuine patriots have never offered unquestioning, unqualified support to leaders who lead them into war. Jesus’ simple statement to Peter in the Garden of Gethsemane still applies to individuals and to nations of our day: “Put your sword back in its place, . . . for all who draw the sword will die by the sword” (Matthew 26:52).

  1. In his treatise Against Faustus the Manichean, Augustine declared: “The real evils in war are the love of violence, the cruel passion for revenge, the blind hatred of the enemy, the sometimes insane uncontrolled resistance to attack, the lust for power and other things of this sort.” Back To Article
  2. “The just-war tradition is as old as warfare itself. Early records of collective fighting indicate that warriors used some moral considerations. They may have involved consideration of women and children or the treatment of prisoners. Commonly they invoked considerations of honor: some acts in war have always been deemed dishonorable, whilst others have been deemed honorable. Whilst the specifics of what is honorable differ with time and place, the very fact of one moral virtue has been sufficient to infuse warfare with moral concerns. The just war theory also has a long history. Whilst parts of the Bible hint at ethical behavior in war and concepts of just cause, the most systematic exposition is given by Saint Thomas Aquinas. In the Summa Theologicae, Aquinas presents the general outline of what becomes the just war theory. He discusses not only the justification of war, but also the kinds of activity that are permissible in war. Aquinas’s thoughts become the model for later Scholastics and Jurists to expand. The most important of these are: Francisco de Vitoria (1486-1546), Francisco Suarez (1548-1617), Hugo Grotius (1583-1645), Samuel Pufendorf (1632-1704), Christian Wolff (1679-1754), and Emerich de Vattel (1714-1767).” (“Just War Theory,” The Internet Encyclopedia of Philosophy) Back To Article
  3. Zbigniew Brzezinski estimated that during the past century, 167,000,000 to 175,000,000 lives were “deliberately extinguished by politically motivated carnage.” See the Discovery Series booklet, Violence: Why It Happens Back To Article
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