Just War Theory
August 24, 2025
Jesus Christ: Yesterday, Today, and Forever ~
I’ve always meant to write a pastor’s column on the Church’s Just War Theory. I can hardly believe that I’ve been a priest for 21 years and still haven’t done so. Well, that day has finally come. In writing this, I am catching America between wars (I better act fast), thus the subject matter can be less contentious and hopefully more clearheaded. People in nations at war, argue over whether or not they should be in that war, or if it is conducted in the way they think it should be conducted. I hope this pastor’s column helps clarify those two questions for you: the ethics of going to war, and the ethics of conducting one.
Almost everything that follows comes from two sources I found on the internet: E. Christian Brugger at https://www.ncregister.com/blog/dmq-just-war-2-s3rijmxb; and ThoughtCo at https://www.learnreligions.com/just-war-theory-catholic-church-542124. I have copied, pasted and arranged what follows, very little are my original words.
In Christ, I Love You,
In Christ, I Love You,
Father Thomas Nathe
History of Just War Theory
The theory of when and how war can be morally justified, goes back at least to the pre-Christian Roman orator Cicero (106 BC–7 AD) and some of his contemporaries. It is picked up again by St. Ambrose (339–397) and then systematically developed by St. Augustine (354-430). Augustine’s account was picked up with minor amendments by St. Thomas Aquinas (1225-1274), whose own rendering was normative for Catholic theorists from the Middle Ages on. The Second Vatican Council (1962-65) re-presents the classical account placing much greater emphasis on the avoidance of war and offering a very forceful condemnation of the use of contemporary weapons of mass destruction (Gaudium et Spes, 80). The current Catechism of the Catholic Church (2307-2317) develops the classical account by conceiving war as a means of legitimate societal self-defense.
Two Types of Justice Concerning War
The Catholic Church distinguishes between two types of justice concerning war: justice before war (jus ad bellum) and justice during war (jus in bello). It is possible for a country to fight a war that meets the conditions for being just, and yet to fight that war unjustly—by, for example, targeting innocent people in the enemy’s country or by dropping bombs indiscriminately, resulting in the deaths of innocent people.
Most of the time, when people discuss just-war theory, they mean justice before the war. There are four conditions described by Saint Augustine through which we determine whether it is just to go to war.
Just Reasons to Go to War: Four Conditions
The current Catechism of the Catholic Church (para. 2309) defines the four conditions that must be met in order for a war to be just:
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 for success.
The use of arms must not produce evils and disorders graver than the evil to be eliminated.
These are hard conditions to fulfill, and with good reason: The Church teaches that war should always be the last resort. So, who makes the determination to go to war and who’s responsible for its conduct?
A Matter of Prudence
The determination of whether a particular conflict meets the four conditions for a just war is left to the civil authorities. In the words of the Catechism of the Catholic Church, “The evaluation of these conditions for moral legitimacy belongs to the prudential judgment of those who have responsibility for the common good.” In the United States, for instance, that means Congress, which has the power under the Constitution (Article I, Section 8) to declare war, and the President, who can ask Congress for a declaration of war. The last time that happened was 1941. Since then, every American President has ordered military action without a Congressional declaration of war. Hence, for America, either Congress can declare war, or the President can order military action which amounts to war, because both possess the moral legitimacy to do so. What can’t be justified in America’s case, is a war waged by governors of states or rogue generals for example, because they do not have the moral legitimacy to do so as per our laws.
But just because the President asks Congress to declare war, or Congress declares war with or without the President's request, or the President orders military action without Congress, does not necessarily mean that the war in question is just. When the Catechism states that the decision to go to war is ultimately a prudential judgment, that means that the civil authorities bear the responsibility for making sure that a war is just before they fight it.
In the absence of publicly available information that allows us to reply to the questions above with moral certainty, citizens should not be quick to judge harshly the military actions taken by their authorities, since factors unknown to them may play decisive roles in decision-making. There is a lot of classified information that the general public does not have access to.
However, a prudential judgment does not mean that a war is just simply because those in authority decide that it is so. It is possible for those in authority to be mistaken in their prudential judgments, to use false information or conclusions in their discernment, or to be maliciously motivated; in other words, they may consider a particular war just when, in fact, it may be unjust.
For example, after all the facts were in about Saddam Hussein’s alleged weapons of mass destruction program, we learned that the American decision to go to war was decided on false information; the truth was that Iraq had no active weapons of mass production (WMD) program. We also learned that by March 2003, the war’s launch date, there existed eminently reasonable doubt as to whether such programs existed; our leaders therefore could not have had moral certainty that they had a just cause.
If this gathering, sifting and assessing is to be done with integrity, then national leaders need virtue, for if they have mixed motives — e.g., to gain access to foreign resources, humiliate and dominate others, impose a religion or ideology, distract from prior or ongoing wrongdoings, et cetera — then respecting just war principles is less likely.
The Conditions for Conducting a Just War
The Catechism of the Catholic Church discusses in general terms (para. 2312-2314) the conditions that must be met or avoided while fighting a war in order for the conduct of the war to be just.
The Church and human reason both assert the permanent validity of the moral law during armed conflict. "The mere fact that war has regrettably broken out does not mean that everything becomes licit between the warring parties."
Non-combatants, wounded soldiers, and prisoners must be respected and treated humanely. The injury or killing of the innocent during war is always forbidden; however, if a bullet goes astray, or an innocent person is killed by a bomb dropped on a military target, the Church recognizes that these deaths are not intended.
Actions deliberately contrary to the law of nations and to its universal principles are crimes, as are the orders that command such actions. Blind obedience does not suffice to excuse those who carry them out. Thus, the extermination of a people, nation, or ethnic minority must be condemned as a mortal sin. One is morally bound to resist orders that command genocide.
"Every act of war directed to the indiscriminate destruction of whole cities or vast areas with their inhabitants is a crime against God and man, which merits firm and unequivocal condemnation." A danger of modern warfare is that it provides the opportunity to those who possess modern scientific weapons—especially atomic, biological, or chemical weapons—to commit such crimes.
