What is Just War Doctrine?

War is indeed a horrifying, terrible evil to be avoided. Therefore, all of us must work for peace. Peace is not simply the absence of war, but the tranquility of right and just order.

By Deacon Frederick Bartels
27 October 2023

In the face of the war which has broken out between Israel and the Islamist militant terrorist group Hamas, there’s no shortage of people posting on social media who seem to take radically opposing stances. On the one hand, some argue for the total annihilation of Palestine, as they deem it necessary to rid the world of Hamas’s inhuman and barbaric brutalities inflicted on innocents—including babies, children, the elderly, and other citizens of Israel. This view, which is essentially “anything goes in war,” is known as total war, a reality that is prohibited in Catholic thought.

On the other hand, there are groups who seem to ignore the atrocities committed by Hamas and insist that Israel has no right to use lethal force to defend itself and its citizens. They argue in favor of Palestine while they ignore the terrible plight of Israel and the unjust attacks it has suffered at the hands of terrorists who seem bent on nothing other than the total destruction of the nation of Israel.

Somewhere in the middle are people asking questions, such as what does an appropriate response by the state of Israel look like? What type of force is a right use of force? And what about non-combatant casualties in Palestine?

My purpose here is not to comment on all the intricacies of this situation or make judgments about the conduct of this particular conflict on the part of Israel, since I do not have the knowledge to do so, but rather to offer the Church’s teaching on Just War doctrine. With this doctrine, the Church offers essential guiding principles in terms of both when a nation has a right to engage in war as a means of self-defense as well as how such a war is to be rightly conducted. To that end, let’s take a look at these principles.

The Duty to Work for Peace and Just Order

In the first place, it is obvious that, following the fall of mankind, we live in a violent world. There is no age left untouched by conflict, war, and its subsequent bloodshed. War is a terrifying reality that always entails not only a loss of combatants on either side, but the loss of innocent human life. For that reason and others, the Church reminds us all of the duty to avoid war and work for peace. As Catholics, we have an obligation to work for peace and maintain just order. The Catechism has this to say:

The fifth commandment forbids the intentional destruction of human life. Because of the evils and injustices that accompany all war, the Church insistently urges everyone to prayer and to action so that the divine Goodness may free us from the ancient bondage of war. All citizens and all governments are obliged to work for the avoidance of war. (CCC 2307, 2308)

Nevertheless, war cannot always be avoided. Vatican II stated: “[A]s long as the danger of war persists and there is no international authority with the necessary competence and power, governments cannot be denied the right of lawful self-defense, once all peace efforts have failed” (Gaudium et Spes, 79 § 4). In plain language, there can be circumstances in which a nation has a right to go to war.

The Right to Wage War

The right to go to war falls under the principle known as ius ad bellum. It is also known as just cause. Within this category, there are several criteria which must together be met. Paragraph 2309 of the Catechism states:

The strict conditions for legitimate defense by military force require rigorous consideration. The gravity of such a decision makes it subject to rigorous conditions of moral legitimacy. At one and the same time:

• the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain;
• all other means of putting an end to it must have been shown to be impractical or ineffective;
• there must be serious prospects of success.

We can summarize these principles involved in the right to wage war in this way:

• The evil inflicted by the aggressor must be lasting, serious, and certain (as opposed to merely threatening language, for example).
• All reasonable alternatives to war have been exhausted. Therefore, war is waged as a last resort.
• War must be declared by a proper governing authority.
• There is a reasonable chance of success. Engaging in war when defeat is reasonably certain is likely to only increase the damage, suffering, and death.

The Right Conduct of War

Next is the right conduct of war principle, known as ius in bello. This principle refers to how war is to be waged. It includes these criteria:

• The principle of proportionality: only as much force is used as is necessary to right the wrong. The Catechism has this to say about proportionality: “the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition” (CCC, 2309).
• The principle of discrimination: soldiers must not intentionally attack non-combatant civilians but only other soldiers and their materials used to wage war.
• Right intention: war is conducted for the restoration of peace and justice as opposed to an intention of revenge or purely out of anger. The moral law tells us that it is never permissible to do evil to bring about an intended good. An evil intention renders an act evil, even if it results in some good outcome such as the defeat of an aggressor.

Some Additional Thoughts

It can be very difficult to determine whether it is just to wage war. Sometimes it involves a straightforward, obvious decision, other times it does not. For example, when President Roosevelt made the decision to go to war against Japan after the Pearl Harbor attack on December 7, 1941, virtually everyone agreed that it was necessary. It was obvious that there was no possibility of negotiating our way out of the war. Japan’s attacks, if left unchecked, would reach the continental U.S., inflicting terrible damage and suffering on innocent citizens. On the other hand, when President George W. Bush made the decision to go to war against Iraq in 2003, his decision was not as morally clear. It was a controversial choice at the time and remains so today.

In the right conduct of war, insuring the principle of proportionality is maintained is fraught with complexities, questions, and difficulties. It’s not always easy to determine when the forced used is too great and therefore disproportionate. The Catechism teaches that “the use of arms must not produce evils and disorders graver than the evil to be eliminated” (CCC, 2309). Obviously it would not be proportionate to use nuclear weapons to entirely annihilate an aggressor nation that launched a few conventional missiles into a defending nation. Doing so would be highly disproportionate. On the other hand, it is often not enough to simply repel an attack and then enter a ceasefire. In that case, the aggressor may use the ceasefire period to re-group, re-arm, and begin another attack causing further bloodshed.

What about terrorist groups like Hamas, whose deeply engrained hate leads to methods that include using human shields, firing missiles to only fall back into the territories of its own people, targeting civilians, beheading children, raping and murdering women, and desecrating the bodies of its victims? It seems Hamas is, and will remain in its generations to come, adamantly bent on exterminating the Jewish people and the nation of Israel. How much force is necessary to stop this outcome and prevent Hamas from parachuting into another music festival in a year or two or five or even twenty, and murdering nearly three hundred civilians? And how far reaching must these efforts be to be effective in establishing peace and just order? What level of force is necessary and therefore proportionate to insure the future safety of Israel and its people against these terrorist attacks? These are difficult questions to solve and people will have different opinions about them.

What about the principle of discrimination? The line between combatants and non-combatants is at times blurred. Military forces have an obligation to avoid deliberately targeting innocent civilians (although there is always some unintended civilian casualties in modern warfare; however, these casualties must be minimized as much as possible). Soldiers in Vietnam and Iraq reported being attacked by people who appeared to be civilians, even by women and children, which sometimes led to seeing civilians as targets. Confusion and uncertainty abound in war, which can easily cause a loss of control. Nevertheless, soldiers have a duty to avoid targeting non-combatants, even if it means they must endure greater risk in doing so.

An example of targeting civilians is found in the decision of the U.S. to drop nuclear bombs on Hiroshima and Nagasaki. The point of doing so was to shock Japan into a ceasefire, thereby preventing further casualties. But what about the 100,000 civilian fatalities? Some attempted to provide justification for these deaths by insisting that the occupants of these cities were actually combatants because Japan had instructed its citizens to fight down to the last man, woman, and child. Additionally, others said that these civilians were providing some type of aid to Japanese soldiers and thus were to be considered combatants. However, just because a government orders its civilians to fight does not automatically make every man or woman (such as the elderly or homemakers) or child a soldier. Furthermore, it seems highly unreasonable to expect large numbers of civilians to withhold every ounce of support from local troops, such as feeding a family-member-combatant at the dinner table or remotely serving the war effort by stitching together uniforms.

In any case, intentionally targeting non-combatants is never morally acceptable, even if it may shorten a war and reduced the number of soldiers killed or injured in battle. It is never morally licit to do evil in order to bring about an intended good. Directly and intentionally targeting non-combatants is an act that is evil in itself.

In Summary

War is indeed a horrifying, terrible evil to be avoided. Therefore, all of us must work for peace. Peace is not simply the absence of war, but the tranquility of right and just order. Peace is found in recognizing every human person is created in the Imago Dei, living in solidarity and love, and doing to others as we would have them do unto us. All people across the world are one human family created by God and redeemed by Christ. Ultimately, the only solution is Christ, the gift of his Spirit, and a life lived virtuously in him. From the Fall of Mankind in the Garden to today, it is incumbent upon Catholics, other Christians, and all people everywhere to exercise the virtue of justice, which is all about right relationships with others. It is in living this way, with the grace of God, that peace is made possible.