War is one of those topics that doesn’t come with a neat and tidy answer.
It raises big, emotional questions for people of faith: Should Christians ever support war? Can violence ever be justified? Is there such a thing as a righteous battle?
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Those aren’t just modern questions — they’ve been around for centuries. And out of that wrestling came the concept of the “just war.” It’s not about glorifying war or making excuses for bloodshed. It’s about drawing moral boundaries in a fallen world where evil sometimes needs to be resisted.
Let’s walk through what the “just war” doctrine is all about, where it came from, and how we as believers, can respond in our complicated world today.
What is the “Just War” theory?
The idea of a “just war” is a moral framework for evaluating whether entering into war is ethically permissible — and, if so, how that war should be conducted. It’s not uniquely Christian, but it was deeply shaped by early Christian thinkers trying to reconcile Jesus’ call to peace with the reality of injustice in the world.
This doctrine seeks to answer two main questions:
1. Is it just to go to war? (jus ad bellum)
2. Is it just to fight in this way? (jus in bello)
In other words, it addresses both the reason for the war and the methods used within it.
Where did the doctrine come from?
(Here’s a hat tip to Google, for doing some heavy lifting here.)
The roots of the “just war” theory go back to St. Augustine of Hippo (354–430 AD), one of the most influential Christian theologians. Augustine struggled with the question of how Christians, called to love their enemies, could ever participate in violence. He concluded that war might be permissible if it served to prevent a greater evil and was carried out with the right intentions — namely, love for neighbor and the desire to restore peace.
Later, St. Thomas Aquinas (1225–1274) expanded on Augustine’s thinking in his work Summa Theologica, where he laid out three criteria for a just war:
- It must be declared by a legitimate authority.
- It must have a just cause (such as self-defense or protecting the innocent).
- It must be fought with right intention — not out of hatred or revenge.
These ideas were further refined over the centuries, influencing both secular and religious approaches to war. Today, elements of just war theory are reflected in international law, including the Geneva Conventions.
For a deeper dive, scholars often cite:
- Augustine’s “City of God“ (Book 19)
- Aquinas’ “Summa Theologica” (II-II, Q. 40)
- “Just and Unjust Wars” by Michael Walzer (a modern ethical perspective)
What does the Bible say?
The Bible doesn’t give us a cut-and-dry manual on warfare.
On one hand, you’ve got Jesus preaching peace and turning the other cheek (Matthew 5:38–48). On the other, the Old Testament is full of military campaigns, many of them initiated by God Himself.
Romans 13:4 describes government as “God’s servant for your good… an avenger who carries out God’s wrath on the wrongdoer.” This verse has been used to support the idea that a government has the right — and sometimes the duty — to use force to restrain evil.
And yet, the same Paul who wrote that also urged us to “live peaceably with all” and not to repay evil for evil (Romans 12:17–21). So the tension remains.
Maybe that’s the point. The Bible invites us into the hard middle ground — where we seek peace and recognize the need for justice.
What should we do?
In today’s world, war isn’t just something that happens in history books or on the other side of the planet. Whether it’s Ukraine, the Middle East, or the latest headlines, conflict is always somewhere on the horizon. So how do we, as followers of Jesus, respond?
Here are a few thoughts:
1. Pray first, always
Prayer is not passive. It’s our first line of defense — and our greatest weapon for peace. Pray for leaders. Pray for peace. Pray for wisdom. Pray for soldiers and civilians alike. We can’t control world events, but we can bring them to the One who does.
2. Speak peace, stand for justice
Supporting peace doesn’t mean we ignore injustice. We can call out evil while still believing that war should always be a last resort. Christians can be voices of reason in a world that often rushes to retaliation.
3. Honor the sacrifice
Many believers have served faithfully in the military with a clear conscience, believing they were protecting others. Let’s not judge them harshly. And if you’re a veteran or have family who served, thank you. Courage and sacrifice are godly virtues.
4. Keep a soft heart
War — even “just” war — leaves scars. Stay sensitive. Let your compassion outweigh your politics. Don’t let a hard world make your heart cold.
In the End…
The doctrine of “just war” doesn’t solve every dilemma. It simply tries to bring ethics into an area often ruled by power and fear. As Christians, we’re called to live in the tension — longing for the day when swords will be beaten into plowshares (Isaiah 2:4), but sometimes having to make hard calls in the meantime.
Until that day comes, let’s be people who pray hard, speak gently, act justly and walk humbly with our God.
EDITOR’S NOTE — This story was written by Tony Martin and originally published by the Baptist Record.
