Based on a detailed investigation of all the facts and supported by the testimony of the surviving Japanese leaders involved, it is the Survey’s opinion that certainly prior to 31 December 1945 and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated.

That was a conclusion of the 1946 U.S. Bombing Survey ordered by President Harry Truman in the wake of World War II.

Gen. Dwight Eisenhower said in 1963, “the Japanese were ready to surrender and it wasn’t necessary to hit them with that awful thing.”

That wasn’t merely hindsight. Eisenhower made the same argument in 1945. In his memoirs, Ike recalled a visit from War Secretary Henry Stimson:

I voiced to him my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives. It was my belief that Japan was, at that very moment, seeking some way to surrender with a minimum loss of “face.”

Admiral William Leahy, Truman’s chief military advisor, wrote:

It is my opinion that the use of this barbarous weapon at Hiroshima and Nagasaki was of no material assistance in our war against Japan. The Japanese were already defeated and ready to surrender because of the effective sea blockade and the successful bombing with conventional weapons.

I put a lot of weight on the assessments of the military leaders at the time and the contemporaneous commission that studied it. My colleague Michael Barone, who defends the bombing, has other sources — a historian and Sen. Daniel Patrick Moynihan — that lead him to conclude Japan would not have surrendered.

This confusion is not surprising. For one thing, there’s what we call the “fog of war” — it’s really hard to know what’s happening currently in war, and it’s even harder to predict which way the war will break.

Second, more generally, there’s the imperfection of human knowledge. Humans are very limited in their ability to predict the future and to determine the consequences of their actions in complex situations like war.

So, if Barone wants to stick with Moynihan’s and the New Republic’s assessments of the war while I stick with the assessments of Gen. Eisenhower, Adm. Leahy, and Truman’s own commission, that’s fine. The question — would Japan have surrendered without our bombing Hiroshima and Nagasaki? — can’t be answered with certainty today, nor could it have been answered in August 1945.

But this fog, this imperfect knowledge, ought to diminish the weight given to the consequentialist type of reasoning Barone employs — “Many, many more deaths, of Japanese as well as Americans, would have occurred if the atomic bombs had not been dropped on Hiroshima and Nagasaki.”

We don’t know that. That’s a guess. We didn’t know that at the time. If Pres. Truman believed that, it was a prediction of the future — and a prediction that clashed with the predictions of the military leaders.

Given all this uncertainty, I would lend more weight to principle. One principle nearly everyone shares is this: it’s wrong to deliberately kill babies and innocent children. The same goes for Japanese women, elderly, disabled, and any other non-combatants. Even if you don’t hold this as an absolute principle, most people hold it as a pretty firm rule.

To justify the bombing, you need to scuttle this principle in exchange for consequentialist thinking. With a principle as strong as “don’t murder kids” I think you’d need a lot more certainty than Truman could have had.

I don’t think Truman’s decision was motivated by evil. I’ll even add that it was an understandable decision. But I think it was the wrong one.