Seventy years ago (Aug. 6 and 9, 1945, to be exact), the United States dropped two atomic bombs on the Japanese cities of Hiroshima and Nagasaki. “Little Boy,” dropped on Hiroshima, was the first atomic bomb to be used in any war. It killed some 90,000 to 160,000 people, about half by explosion and half by burns, radiation and injuries, over the next couple of months. “Fat Man,” dropped on Nagasaki three days later, killed about 40,000 to 80,000. Far more civilians than Japanese military were among the dead.

These are the only two nuclear bombs to have ever been used in warfare: the first two — and so far, the last two.

That they are the last two is some cause for celebration 70 years later. That they were the first two — and dropped by the United States — is not.

Why did the U.S., with the advice and consent of the Allies, drop the atomic bombs?

Germany had been decisively defeated in May of 1945. Japan was, by this time in the war, in bad shape, although ready to fight to the last. Realizing the U.S. was intent on invading its homeland, Japanese leaders even conscripted some 28 million male and female civilians to aid the 2.3 million soldiers to fight off U.S. forces: the so-called Volunteer Fighting Corps, Kokumin Giy Sentai. This — in addition to the large numbers of civilians working in support industries for the Japanese military — blurred the line between civilian and military personnel, thereby making it increasingly difficult to distinguish between combatant and noncombatant.

American military studying the projected cost in human lives of the invasion of Japan estimated that the number of Allied lives that would be lost in the invasion ranged from 25,000 to well over 500,000. Estimates of Japanese lives that would be lost ranged from around 3 million to 4 million. That is what brought U.S. military leaders to consider means — any means — to reduce the high casualty counts of the invasion.

One means used months before the dropping of the two atomic bombs actually killed far more Japanese civilians — the firebombing of major Japanese cities with incendiary cluster bombs, filled with jellied gasoline (better known as “napalm”). In the firebombing of Tokyo alone, 80,000 to 130,000 civilians were killed. More than 50 cities were firebombed from May to August 1945.

The decision to drop atomic bombs in August was an extension of these previous efforts. Hiroshima, which had not been firebombed, was chosen because of its military and industrial significance to the Japanese war effort. The city included some 40,000 military personnel. Nagasaki was chosen for the same reasons, although it was a secondary target (the original city to be bombed being Kokura). There were about 10,000 military personnel in Nagasaki.

On the night of Aug. 9, 1945, at 10pm, President Harry Truman addressed Americans over the radio. “I realize the tragic significance of the atomic bomb. … We have used it against those who attacked us without warning at Pearl Harbor, against those who have starved and beaten and executed American prisoners of war, against those who have abandoned all pretense of obeying international laws of warfare. We have used it in order to shorten the agony of war, in order to save the lives of thousands and thousands of young Americans. We shall continue to use it until we completely destroy Japan’s power to make war. Only a Japanese surrender will stop us.”

More atomic bombs were slated to be dropped as soon as they were produced, but Emperor Hirohito capitulated on Aug. 14, stating, “The enemy now possesses a new and terrible weapon with the power to destroy many innocent lives and do incalculable damage. Should we continue to fight, not only would it result in an ultimate collapse and obliteration of the Japanese nation, but also it would lead to the total extinction of human civilization.”

I have given nearly every convincing reason that has been mustered in defense of dropping the two bombs: The Japanese attacked us first; they had no intention of surrendering; far more lives would have been lost had we not dropped the bombs; and the Japanese themselves had completely blurred the lines between military and civilian.

I have also noted (via Truman’s remarks) the savagery of the Japanese themselves in conducting the war, especially their brutality against Allied prisoners. (For those who doubt this, please read Laura Hillenbrand’s excellent but horrifying account in Unbroken.)

It is clear that, lacking the West’s just-war doctrine, the Japanese observed no limits to their cruelty, and this cruelty, as part of Imperial Japanese policy, predated World War II.

In the infamous “Rape of Nanking” (which occurred at the end of 1937 and continued into early 1938), upwards of 300,000 Chinese civilians were slaughtered. That is only one of a number of instances of massive Japanese brutality, which culminated in Emperor Hirohito’s “Three Alls Policy,” wherein he instructed his soldiers, “Kill all; burn all; loot all.”

If that weren’t enough, like the Nazis, the Japanese were using prisoners for medical experimentation (including live vivisections) and using biological weapons in experimentation and in actual warfare. Estimates of the number who died from these atrocities is about half a million. In fact, in its “Operation Cherry Blossoms at Night,” the Japanese planned to infect America’s West Coast with pathogens on Sept. 22, 1945, but the dropping of the two atomic bombs brought them to surrender in mid-August, just weeks before the planned attack.

So, one would think, with all of this, that dropping the atomic bombs was justified. Many, in fact, do maintain precisely that.

But the Catholic Church presents an obstacle to that easy conclusion: the above-mentioned just-war doctrine, a centuries-old doctrine formed historically under the guidance of the Church.

The best argument for the just-war doctrine is precisely the kinds of atrocities committed by the Japanese, who had not been historically formed by it. Without it, they were free to do anything to win a war, to civilian and soldier alike. To stop them, the U.S. chose to violate the just-war demand that limits killing to soldiers and spares civilians, betting that the shock of the indiscriminate incineration of entire cities of men, women and children (first by firebombing and then atomic bombing) would bring the Japanese to surrender.

It did. But the issue is not whether using any means to win a war is politically effective. What is at stake is the moral effect of removing any moral limit to our actions and allowing the ends to justify any means.

We now live in a society largely governed by that principle, so that, for example, the end of psychological and physical health justifies abortion and the sale of fetal organs thus procured.

I have no doubt that many lives could be saved by freshly harvested organs from aborted babies, just as I have no doubt that saving lives by the slaughter of innocent children has returned us to a sub-pagan moral darkness.

So this is not a stale history lesson. Indeed, in regard to the just-war doctrine, we face the same morally hazardous situation today as we did with Japan. Islamic jihadists have likewise not been formed by the just-war doctrine, and so they have no compunction about crucifying children, beheading both military personnel and civilians, keeping captured women in sexual slavery and using women and children for shields and living bombs — any means to win the war. Will we stoop to their barbarism to defeat them?

The Church does not reject war, which is sometimes necessary as an act of self-defense. But she places moral limits because where there are no moral limits to war, there are no limits to barbarism. Thus, the Church asserts that, in carrying on a justified war, “the use of arms must not produce evils and disorders graver than the evil to be eliminated” (Catechism, 2309). One of the greatest evils is the removal of the distinction between combatants and civilians.

And so, declares the Church,

“‘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” (Catechism, 2314).

The question is not whether using any means is effective. Certainly dropping the atomic bombs ended the war, and may even have saved lives. The problem is the inhumanity that flows directly from using any means to justify such ends — and devolving into the very barbarism that we are trying to defeat.

Benjamin Wiker is an associate professor of political science at Franciscan University

and a senior fellow of Franciscan’s Veritas Center for Ethics in Public Life.