Theology of War and Peace

Within Christianity several different theological traditions of war and peace have developed during the last two millennia.


Practicing love as Jesus taught and rejecting violence, the Christian church was largely pacifist for its first 300 years.

The tone was set by Jesus’ original disciples who adhered to their master’s teaching even though it cost them their lives. King Herod had James, one of the sons of Zebedee, killed with a sword (Acts 12:2). Tradition holds that nine others were martyred for their faith and that only John lived to old age. An exception, of course, was Judas the betrayer who hanged himself (Matthew 27:3-5).

Although some early Christians may have served in the Roman army, most did not. They refused to bow before the Roman emperor and Roman gods and to pledge allegiance to the Roman state. As a result, they experienced waves of persecution. As this occurred, they did their best to follow Jesus’ teaching about forgiveness and love for enemy.

However, this changed after Roman Emperor Constantine (who reigned from 306 to 337 CE) became a Christian convert. He allowed Christians to practice their faith without persecution, supported the church financially, built basilicas, appointed Christians to high office, and convened an ecumenical council at Nicaea to settle doctrinal disputes. With this close association of church and state, pacifism receded as the dominant doctrine.

Nevertheless, commitment to pacifism continued in religious orders, most notably with Francis of Assisi (1182-1226), and among other Catholic clergy and laity. It gained expression as three peace churches formed: Mennonites in 1540s, Society of Friends (Quakers) around 1650, and Church of the Brethren in 1708. Pacifists are found today as a minority in Protestant denominations and within Roman Catholic and Orthodox churches.

Just War

In the fourth century CE as church and state became closer together, the issue arose of when it was justifiable for the state to go to war.  Taking the lead, Augustine (354-430), bishop of Hippo, started with the idea that in a sinful world it is necessary to prevent aggression against innocent victims. Drawing ideas from Roman moral law and Bishop Ambrose of Milan (340-397), Augustine developed criteria on when it is permissible to go to war and on conduct in the course of war. This was further developed by other theologians, notably Thomas Aquinas (1225-1274).

Just war principles, as explained by the U.S. Conference of Catholic Bishops in The Challenge of Peace (1983), provide criteria when recourse to war is permissible, including:

  • Just cause, such as to protect innocent life, to secure basic human rights.
  • Declared by competent authority.
  • Last resort only when all peaceful alternatives have been exhausted.
  • Probability of success.

Criteria for conduct of war include:

  • Damage inflicted and costs incurred by war must be proportionate to the good of taking up arms.
  • The lives of innocent persons may never be taken directly.

As Protestant churches split off from the Catholic Church, some of them, such as the Lutherans, retained just war principles. Others made modifications without becoming wholly pacifist.


The Catholic Church itself abandoned just war principles during Crusades of the 11th to 13th centuries. It was military action initiated by the Church itself. The major goal was to assure free access to Jerusalem which had been under the control of a succession of Muslim rulers since 636 C.E. Smaller crusades campaigned against pagans and heretics in Western Europe.

The First Crusade, proclaimed by Pope Urban II in 1095, set the tone. Kings and nobles from Western Europe raised funds and recruited soldiers, especially from the peasantry who lacked military discipline. On the way to Jerusalem they pillaged cities. They laid siege to Antioch, stormed the city, massacred Muslim inhabitants. The same occurred when they entered Jerusalem in July 1099, killed thousands of Muslim and Jewish civilians, and destroyed mosques.

Muslims fought back and regained control of Jerusalem in 1187. The Third Crusade (1189-1192) led to a truce which gave Christians access to holy sites. The Fourth Crusade (1202-04) never reached Jerusalem and instead redirected its efforts to conquer and occupy Constantinople, the seat of the Eastern Orthodox Church which had split from the Roman Church in 1054.  Other crusades ensued until the fall of Acre, the last Christian stronghold, in 1291.

Eastern Orthodox

Within Christendom the just war theory never caught on in the east as it did in the west.  As the Eastern Orthodox Church divided from Rome, it adopted its own approach to war and peace.

As explained by Fr. Philip LeMasters: “Orthodoxy has neither a crusade ethic nor an explicit just war theory. Instead, the church tolerates war as an inevitable, tragic necessity for the protection of the innocent and the vindication of justice.

“The canons of the church suggest a period of repentance for those who have killed in war, which indicates both that taking life is spiritually damaging and that bloodshed falls short of Christ’s normative way of non-resistant, non-violent love.

“Peacemaking is the common vocation of all Christians, but the pursuit of peace in a corrupt world at times inevitably requires the use of force. In such circumstances, the church provides spiritual therapy for healing from the damaging effects of taking life” (“Orthodox Perspectives on Peace, War and Violence” in Ecumenical Review, March 2011).

Although Protestant denominations aren’t in the direct lineage of Eastern Orthodoxy, some of them take a similar regretful-but-sometimes-necessary approach to war.  Within their membership they recognize both conscientious objectors and those who participate in war.

Just Peace

In the last 25 years a new emphasis has developed within Protestantism that seeks to go beyond the pacifism-just war debate, promotes conflict prevention and resolution, and makes a strong connection between peace and justice.

In the 1990s Professor Glenn Stassen from Fuller Theological Seminary and other scholars developed a The Just Peacemaking Paradigm with focus upon nonviolent direct action, threat reduction, conflict resolution, human rights, just economics, and strengthened international cooperation (http:/ practices/).

In 2011 the World Council of Churches issued An Ecumenical Call to Just Peace that makes justice the inseparable companion of peace.Nonviolent resistance is central to the Way of Just Peace.” So are efforts to transform conflict. Even so, “There are extreme circumstances where, as the last resort and the lesser evil, the lawful use of armed forces may become necessary in order to protect vulnerable groups or people exposed to imminent lethal threats.” This would be an expression of the “responsibility to protect”, including “just policing”. But this would exclude other justifications of the use of military power. Just Peace also emphasizes caring for creation.


These several perspectives on war and peace challenge us as we seek to live in God’s kingdom here and now. It seems clear that the aggressive warfare of Joshua’s conquest of Canaan and the Crusades have no proper place in God’s kingdom on earth. For many Christians Jesus’ command to love our enemies precludes them from participating in war. You’re not loving your enemies if you are trying to kill them.

Other committed Christians sincerely believe that war is necessary in some circumstances to resist aggression and protect the innocent. But in spite of these differences, we can all believe that peace is the preferred alternative. Therefore, we are all called to be peacemakers, which is the focus of another section.