Q. Last summer we remembered the 75th anniversary of the U.S. bombing of Hiroshima and Nagasaki in 1945. I’ve heard some Catholic say the bombings were justified because they saved American lives. Can you explain just war thinking and how it applies to these bombings? —Robert

A. The classical Catholic just war account derives from St. Augustine (354-430), who himself draws upon the theories of Cicero and St. Ambrose. Augustine’s account was picked up with minor emendations by St. Thomas Aquinas (1225-1274), whose own rendering was normative for Catholic theorists from the Middle Ages. The Second Vatican Council 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). And the Catechism of the Catholic Church (2307-2317) develops the classical account by conceiving war as a means of legitimate societal self-defense. 

Just war theory traditionally has been formulated as a set of moral principles that act as conditions that need to be met in order for the decisions entailed in launching and prosecuting wars to uphold the requisites of justice. The most important is that wars be waged to correct some manifest injustice; this is referred to as the principle of just cause. Others include that war must be the best available remedy for correcting the injustice, and therefore solutions short of war should be employed if possible (principle of last resort); that public authority — and public authority alone — rightly decide questions of going to war (principle of public authority); that all evil intentions must be excluded in war’s declaring and prosecuting (principle of rightful intention), which entails (inter alia) the wrongness of the intention to kill non-combatants (principle of discrimination); that there should be a reasonable probability of success; and that if waging war would bring about a worse state of affairs, or if actions in war are more violent than what is necessary to accomplish the war’s just aims, then having recourse to war would be unjust (principle of proportionality). Augustine and Aquinas include a condition not found in contemporary accounts, which prohibits declaring falsehoods and breaking promises to an enemy (principle of good faith), which does not however require that one’s purposes or the meanings of one’s actions be declared.

You ask about Hiroshima and Nagasaki. As you say, some Catholics still defend the United States’ decision to drop A-bombs on the two cities in August 1945. Their arguments almost always include the claim that the bombings saved lives — especially U.S. lives — hastening an end to the war. Whatever truth there is in the claim —and the “saving lives” claim is disputable — the intentional targeting of the civilian Japanese populations clearly falls under the condemnation of Vatican II: “Any act of war aimed indiscriminately at the destruction of entire cities or extensive areas along with their population is a crime against God and man himself. It merits unequivocal and unhesitating condemnation” (Gaudium et Spes, 80), which was quoted again in full in the Catechism (2314). 

This condemnation is a conclusion of the classical principles of rightful intention and discrimination. Catholic moral theory, of which just war theory is a subset, has always taught the absolute immunity of the innocent: no intentional killing — not in war, not in peacetime, never. 

Defenders of the bombings justify the decision by reasoning that greater good was achieved by obliterating these cities and their peoples.

This kind of reasoning is called “proportionalism” because it assesses the act’s morality by weighing the proportion of good to be gained by the bombings against the evils being threatened. Since good apparently outweighed evil, there was justification for doing the act, even though evil had to be done. The evil, defenders say, is a justifiable evil, a lesser evil, a pre-moral evil.

Pope St. John Paul II criticizes this reasoning because it ends up justifying “deliberate consent to certain kinds of behavior” condemned by the Catholic Church (Veritatis Splendor, 75). On this basis he judges proportionalism unreasonable and unCatholic: 

“Such theories however are not faithful to the Church’s teaching, when they believe they can justify, as morally good, deliberate choices of kinds of behavior contrary to the commandments of the divine and natural law. These theories cannot claim to be grounded in the Catholic moral tradition” (76). 

You might ask how just war thinking applies to other U.S. military interventions — for example, in Afghanistan, Syria, Iraq and Libya. 

In order to judge the justice of each intervention, we need to assess whether the moral principles set forth above were respected in their initiating and prosecuting:

1. Were the claims against our enemies just, or exaggerated or fabricated?
2. Was the governing intention to correct the injustice or were there mixed motives?
3. Were reasonable non-military alternatives exhausted or was the judgment to take military action premature?
4. Did the proper authorities authorize the conflict or were they sidestepped in the rush to war?
5. Did we ever use more violence than necessary or other immoral means to accomplish our objectives?
6. Was there from the start a reasonable probability of success? 

Some of these questions can be difficult to answer. Assessing the reliability of intelligence and so getting clear on what the enemy is really up to; understanding his rightful claims to territorial hegemony; if he is engaged in a civil war, understanding the rights of either side to prosecute their own offensives; assessing the legality of hostile foreign intervention; gaining realistic foresight about outcomes and predictions of success — these require decision-makers to gather, sift through and assess the reliability of large amounts of information. 

If this gathering, sifting and assessing is to be done with integrity, our leaders need virtue, for if they have mixed motives — e.g., to gain access to foreign oil reserves, humiliate our enemies, establish U.S. military superiority in a region, distract from prior or ongoing wrongdoings — then respecting just war principles is less likely. 

Though leaders frequently hide their intentions from the public, they themselves know what they do and why they do it. They know why they authorize this or that air strike, or authorize more violence than needed to accomplish just military objectives, or sanction actions that cause disproportionate destruction; and they certainly know when they authorize the killing of civilians through bombings, or other coercive means, including sanctions and blockades. Decision-makers therefore are required to police their own motives and maintain a steely resolve to uphold the requirements of justice. Those who lack virtue find this difficult.

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.

This does not mean that we shouldn’t judge our leaders’ actions when facts come to light. For example, after all the facts were in about Saddam Hussein’s alleged weapons of mass destruction program, Pope John Paul II’s earlier criticisms of a “preemptive war” against Iraq were vindicated. We learned that the U.S. decision to go to war was decided on false information; the truth was that Iraq had no active 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. The decision seems also to have violated the principles of last resort and probability of success. 

As to the other military interventions named above, I have not done the hard work necessary to secure a confident moral judgment.