Just War Theory Principles (Part 2)

PMT 2013-006b by Kenneth L. Gentry, Jr.

Below is a study of the biblical principles of Just War.

In my last non-eschatology blog article I opened the question of Just War Theory. There I focused briefly on Scripture and war. In this issue I will summarily state the principles of Just War Theory and provide biblical references backing them up.

In keeping with the peaceable intentions of the Christian faith, Just War Theory posits the following principles:

(1) The Principle of Just Cause. A just war can only be fought to redress a grievous wrong suffered and must be engaged with a view to redressing that injury. The right to personal self-defense is always just. We see this legally stated on the personal level in God’s Law: “If the thief is caught while breaking in, and is struck so that he dies, there will be no blood guiltiness on his account” (Exo. 22:2). We see it on the social level in granting the magistrate the right to capital punishment for prescribed crimes: “He who strikes a man so that he dies shall surely be put to death” (Exo. 21:12).

God condemns “princes [who] are like wolves tearing the prey, by shedding blood and destroying lives in order to get dishonest gain” (Eze. 22:27). The encoding of legislation in the Law regarding national armies takes the right to self defense from the personal and local levels to the national level: “Then Amalek came and fought against Israel at Rephidim. So Moses said to Joshua, ‘Choose men for us, and go out, fight against Amalek’” (Exo. 17:8-9; cp. 1 Sam. 30:3, 18-19). The blessings of God include victory against the enemy who assails: “The Lord will cause your enemies who rise up against you to be defeated before you; they shall come out against you one way and shall flee before you seven ways” (Deut. 28:7). Even the New Testament commends just war by placing in the “Hall of Faith” those who “became mighty in war, put foreign armies to flight” (Heb. 11:34).

(2) The Principle of Last Resort. In matters of national relations where tensions are raised, Just War Theory seeks to insure peace and safety. Therefore, just war can only be waged as a last resort requiring that all reasonable non-violent options must be exhausted before the use of force can be justified. Even regarding cities that threatened Israel we read: “When thou comest nigh unto a city to fight against it, then proclaim peace unto it. And it shall be, if it make thee answer of peace, and open unto thee, then it shall be, that all the people that is found therein shall be tributaries unto thee, and they shall serve thee. And if it will make no peace with thee, but will make war against thee, then thou shalt besiege it” (Deut. 20:10-12).1

(3) The Principle of Legitimate Authority. A war is just only if it is waged by a legitimate authority. Vigilante justice and gang warfare are not God-ordained means of social conduct. In fact, these are debilitating features of social chaos evidencing the breakdown of moral order. Even just causes require just means of resolution. To plan war is to plan death, which requires duly sanctioned moral authority. This is possessed only by the civil magistrate who is ordained to wield the sword in providing for the defense of its citizenry.

According to Romans 12:19 vengeance belongs to God who will repay the evildoer (Rom. 12:19). Just three verses later Paul begins pointing out that God has given the right to avenge wrongdoing to the civil magistrate who is the “minister of God” in this respect (Rom. 13:1-4). “Governors [are] sent by him for the punishment of evildoers and the praise of those who do right” (1 Peter 2:14), which includes punishment of whole nations that threaten evil against another nation.

(4) The Principle of Successful Prospect. A war can only be just if it is fought with a reasonable chance of success. Human life is precious, in that man is created in the image of God (Gen. 1:26-27). God has a special concern for man, his highest creature: “What is man, that Thou dost take thought of him? And the son of man, that Thou dost care for him?” (Psa. 8:4). God ordains the protection of human life: “Whoever sheds man’s blood by man his blood shall be shed, for in the image of God He made man” (Gen. 9:6). This, of course, prohibits suicide, even at the national level.

In a parable, Jesus touches on this principle of war: “Or what king, when he sets out to meet another king in battle, will not first sit down and take counsel whether he is strong enough with ten thousand men to encounter the one coming against him with twenty thousand?” (Luke 14:31). David expresses such a concern regarding the prospect of utter defeat: “David inquired of the Lord, saying, ‘Shall I pursue this band? Shall I overtake them?’ And He said to him, ‘Pursue, for you shall surely overtake them, and you shall surely rescue all’” (1 Sam. 30:8). The righteous seek safety, not destruction: “My God, my rock, in whom I take refuge; my shield and the horn of my salvation, my stronghold and my refuge; my savior, thou dost save me from violence. . . I am saved from my enemies” (2 Sam. 22:3-4). Consequently, wide scale deaths and injury incurred in a hopeless cause are not morally justifiable, being a form of national suicide.

(5) The Principle of Peaceful Objectives. The ultimate goal of a just war is to re-establish peace and safety. The historical goal of the kingdom of God clearly teaches this primary historical objective:  “He will judge between the nations and will render decisions for many peoples; and they will hammer their swords into plowshares, and their spears into pruning hooks. Nation will not lift up sword against nation, and never again will they learn war” (Isa. 2:4). As a counter example, Islam as a religion and culture has from its founding in Muhammad until the present been in a constant state of war with other cultures.

The just war goal of securing peace embodies the biblical principle that we should “not be overcome by evil, but overcome evil with good” (Rom. 12:21). David, though a “man of war” (1 Chron. 28:3), exhibits his righteous desire for peace: “Too long has my soul had its dwelling with those who hate peace. I am for peace, but when I speak, they are for war” (Psa. 120:6-7). Rushdoony observes: “Even in wartime, God’s purpose, the furthering of life for the purposes of godly dominion, must be obeyed.” 2

(6) The Principle of Proportionate Means. Just war is God-sanctioned violence. But the violence meted out in war must be proportional to the injury suffered. For instance, the laws governing capital punishment constrain the state by not allowing the magistrate to capitally punish a thief (Exo. 22:7) or to put to death the murderer’s family: “Fathers shall not be put to death for their sons, nor shall sons be put to death for their fathers; everyone shall be put to death for his own sin” (Deut. 24:16).3 Likewise, the aim of war must be constrained by principles of proportionality, according to the lex talionis principle of  “an eye for an eye” (Exo. 21:24; Lev. 24:20f).

Rushdoony observes that “total war is prohibited, either against man or against his land.” 4 Napoleon’s utter humiliation of his enemies led to Prussian military instructor, Karl von Clausewitz,  developing the concept of “total war.” But God’s Law forbids total war: “When you besiege a city a long time, to make war against it in order to capture it, you shall not destroy its trees by swinging an axe against them; for you may eat from them, and you shall not cut them down. For is the tree of the field a man, that it should be besieged by you? Only the trees which you know are not fruit trees you shall destroy and cut down, that you may construct siegeworks against the city that is making war with you until it falls” (Deut. 20:19-20).

(7) The Principle of Civilian Immunity. When just war is engaged the military plans and actions must discriminate between combatants and non-combatants. Unarmed civilians are never legitimate targets of war, and every reasonable effort must be taken to avoid killing them. Civilian deaths are tolerable only as accidental, unavoidable collateral damage resulting from an attack on a legitimate military target.

The Scriptures reflect this principle in various places. Armed combatants are the target of just war: “Let not him who bends his bow bend it, nor let him rise up in his scale-armor; so do not spare her young men; devote all her army to destruction” (Jer. 51:3). “When the Lord your God gives it into your hand, you shall strike all the men in it with the edge of the sword. Only the women and the children and the animals and all that is in the city, all its spoil, you shall take as booty for yourself; and you shall use the spoil of your enemies which the Lord your God has given you” (Deut. 20:13-14). Again, this embodies the principle of man being the image of God and under his protections.


These principles, long maintained in Christian culture and established in biblical law, must guide us in one of the most fearsome powers of government: the right to wage war. God’s Word directs us in all of life, and is especially important in governing that which can end life and culture.


  1. Israel had God-defined borders (Gen. 15:18; Exo. 23:31; etc.) and could never legitimately possess imperialistic pretensions. This passage is not dealing with the special, limited Holy War which secured the Promised Land: “Thus you shall do to all the cities that are very far from you, which are not of the cities of these nations nearby” (Deut. 20:15).
  2. R. J. Rushdoony, Institutes of Biblical Law (Vallecito, Calif.: Ross, 1973), 1:355.
  3. Those who claim court governed capital punishment is merely revenge encoded in law must recognize severe limits on the offended: they cannot punishment the criminal immediately (without trial), torture him, punish his family, or do anything beyond the limits of the law. Capital punishment actually curtails personal revenge.
  4. Rushdoony, Institutes, 1:355.

Helpful studies

Christ of the Covenants (book)
by O. Palmer Robertson
For more information or to order: click here

Classic study of covenant theology. Presents the richness of a covenantal approach to understanding the Bible. Treats the Old Testament covenants from a successive standpoint. This book shows how the covenants (and not dispensations) structure Scripture. Indeed without understanding the covenants, one will inevitably fail to understand much of Scripture.

O. Palmer Robertson (B.D., Westminster Theological Seminary; Th.M., Th.D., Union Theological Seminary, Virginia) is director and principal of African Bible College, Uganda. He previously taught at Reformed, Westminster, Covenant, and Knox Theological Seminaries, has served as pastor of four congregations, and has also lectured in Asia, Europe, and Latin America.

Three Views on the Millennium and Beyond
ed. by Darrell L. Bock
For more information or to order: click here

Gentry, Craig Blaising, and Robert Strimple present three views on the millennium: progressive dispensationalist, amillennialist, and reconstructionist postmillennialist viewpoints. Includes separate responses to each view.

330pp. Zondervan. 3rd Printing. Paper. Edited by Darrell L. Bock

“A meaty book amply sprayed with biblical texts, not one of those pop quickies about the Kosovo conflict” (Associated Press).

“The religionists seem to be a bit more responsible and less adventuresome than their secular counterparts. There are things to cheer on the religious publishing front” (Martin E. Marty).

A helpful ddition to a helpful series” (Bibliotheca Sacra).

“A careful articulation of the postmillennial perspective” (Craig S. Keener, Revelation: The NIV Application Commentary , p. 472).

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2 thoughts on “Just War Theory Principles (Part 2)

  1. Kenneth Gentry October 2, 2013 at 6:39 am

    Richard wrote to me on Facebook:

    “In your first entry on alcoholic bevs you said “I would like to point out up front that I myself do not drink wine or any form of alcohol. For me this is a purely ethical issue rather than a personal one.” Did you mean to say the opposite? I’m confused.”

    My reply is:

    Perhaps that could have been more clearly stated. I do not drink alcohol. I don’t like the taste that much, plus I have a genetic liver problem. So my point is: when I argue for the right for Christians to drink alcohol, it is not because I personally indulge and am trying to justify myself. It is purely an ethical issue: God’s word allows the use of alcohol even though personally I don’t imbibe.

  2. Aaron November 5, 2022 at 10:09 am

    I really like this post a lot. I was not too familiar with most of the seven principles, at least not in this structured format. I feel like the United States has been in a lot of wars which violate one or more of these principles. It makes it hard for me to understand why we should “support our troops” and “thank you for your service” IF they are involved in an unjust war. And I wonder what choices a soldier actually has available if they believe, or come to believe, a war they are fighting is unjust after they are already involved. Perhaps it is a “dishonorable discharge.” I do not know. There are also situations where a nation is not supplying troops, but they are supplying weapons and finances. I consider this scenario as falling under the judgment/analysis of just war principles.

    In 2022, I personally believe the U.S. is involved in an unjust war by sending billions of dollars and other resources to Ukraine. It seems to me Russia is actually following most of the seven principles. Russia has shown lots of restraint and is open to more negotiations (principle of last resort). They are minimizing civilian casualties, unlike some of the Ukrainian groups using civilians as human shields (civilian immunity). Perhaps the western sanctions are also harming civilians if we include Africans who are suffering from issues related to access to grain and fertilizers. Russia has peaceful objectives, whereas the U.S. has hegemonic objectives. The Donbass have been oppressed by the Ukrainian government since 2014. The West has violated the Minsk agreements. I also find Russia to have good prospects for success, whereas the West is just prolonging the crisis.

    I do not think hegemony fits with the goals of postmillennialism. We cannot achieve postmillennial peace when one nation wants to control the whole world. I think current events related to Ukraine might possibly be God bringing an end, or at least a severe dent, to U.S. hegemony, just as God brought an end to Imperial China, the Ottoman Empire, the Mongol Empire, and more. (I mentioned these since I recently studied their fascinating histories through “The Great Courses”). I think the goal of postmillennialism is a multipolar world, not a hegemonic world. Having said that, my understanding is imperfect, amateur, and needs much growth.

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