However, it is my judgment in these things that when you see something that is technically sweet, you go ahead and do it and you argue about what to do about it only after you have had your technical success. That is the way it was with the atomic bomb. I do not think anybody opposed making it; there were some debates about what to do with it after it was made. I cannot very well imagine if we had known in late 1949 what we got to know by early 1951 that the tone of our report would have been the same.

Science wants the fruits of science, and it does not tolerate much doubt about the goodness of those fruits. ... Scientists had a bad conscience about making the atom bomb, it’s fair to say, but their doubts were not prompted, still less endorsed by their science.

Preparedness to use atomic bombs against men and women and children is a proclamation of faith, a confession of confidence in the rightness and effectiveness of human slaughter as a means of seeking safety and of maintaining justice.

It was my responsibility that this world got itself an atom bomb, because there were only a handful of nuclear physicists in the thirties — only a handful. And we were all beating the desk and saying "How wonderful it will be if we discover atomic fission."

[atomic bombs are] born not that men might live, but that men might be killed.

The free world, at least dimly aware of these facts, has naturally embarked on a large program of warning and defense systems. That program will be accelerated and extended. But let no one think that the expenditure of vast sums for weapons and systems of defense can guarantee absolute safety for the cities and citizens of any nation. The awful arithmetic of the atomic bomb does not permit of any such easy solution. Even against the most powerful defense, an aggressor in possession of the effective minimum number of atomic bombs for a surprise attack could probably place a sufficient number of his bombs on the chosen targets to cause hideous damage.

The news today about "Atomic bombs" is so horrifying one is stunned. The utter folly of these lunatic physicists to consent to do such work for war-purposes: calmly plotting the destruction of the world! Such explosives in men's hands, while their moral and intellectual status is declining, is about as useful as giving out firearms to all inmates of a gaol and then saying that you hope "this will ensure peace". But one good thing may arise out of it, I suppose, if the write-ups are not overheated: Japan ought to cave in. Well we're in God's hands. But He does not look kindly on Babel-builders.

The President had unequivocally said that we would never use atomic weapons except against an aggressor. None of us like the idea of using them -- not least those of us who are engaged in their production -- but these reservations, which are the result of our moral principles, can be used, and are being used, by our enemies to trap and confound us. We must see the problem in its full perspective. We are not making weapons for conquest or aggression, or to impose our system on other peoples. Our sole purpose in having them is that we may not fall easy prey to others who have no such reservations, -- and who lack them because they lack the moral springs from which they might arise. Our reservations and principles do us proud but we cannot allow them to disarm us. For if ever they did, those principles would disappear from the face of the earth.

Perhaps there is some hope that its capacity for death and terror among the defenseless may restrain nations from using the atom bomb against each other, just as in the last war such fears made them avoid employment of the new and deadlier poison gases developed since World War I. However, I am forced to a reluctant conclusion that for the security of my own country which has been the guiding principle in my approach to all problems faced during my career, there is but one course open to us: Until the United Nations, or some world organization, can guarantee- and have the power to enforce that guarantee- that the world will be spared the terrors of atomic warfare, the United States must have more and better atomic bombs than any potential enemy.

The advent of Atombomb into a world of varying moral standards and uncertain international friendships has made everyone aware for the first time of the awful fact that, if the world ever lost its spiritual and moral equilibrium, it was now possible completely to eliminate life itself.

I realize the tragic significance of the atomic bomb. Its production and its use were not lightly undertaken by this Government. But we knew that our enemies were on the search for it. We know now how close they were to finding it. And we knew the disaster which would come to this Nation, and to all peace-loving nations, to all civilization, if they had found it first. That is why we felt compelled to undertake the long and uncertain and costly labor of discovery and production. We won the race of discovery against the Germans. Having found the bomb we have used it. 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.

In August 1945 British military intelligence unwittingly performed a splendid experiment in the social psychology of natural scientists. They delivered the news of Hiroshima to interned German atomic scientists, and secretly recorded the conversation that resulted. Only fragments of the record have got past restrictions on “classified” material, but they are enough to reveal the German scientists’ mentality—their soul, if I may use an outmoded term. They were conscience-stricken; they had failed “German science.” Casting about for reasons, they took note of the obvious disparity in size: the American A-bomb project had been enormously larger than their own. But that contrast only deepened the anguish of self-accusation. “We would not have had the moral courage,” Werner Heisenberg, the originator of the Uncertainty Principle, exclaimed, “to recommend to the government in the spring of 1942 that they should employ 120,000 people.” ...
Implicit in that soul-searching was one measure of the scientist’s social and moral worth: his capacity to beat the competition, to win, whether fame for himself or wars for his country, or both together. When Heisenberg emerged from internment and discovered that the winners were uneasy, he turned to a different measure of the scientist’s worth. He and his colleagues had shown moral courage, he decided, of a higher order. They had dragged their feet, to withhold the A-bomb from their Nazi masters. ...

The atomic bomb had dwarfed the international issues to complete insignificance. When our minds wandered from the preoccupations of our immediate needs, we speculated upon the possibility of stopping the use of these frightful explosives before the world was utterly destroyed. For to us it seemed quite plain that these bombs and the still greater power of destruction of which they were the precursors might quite easily shatter every relationship and institution of mankind... war must end and that the only way to end war was to have but one government for mankind.

The lethal possibilities of atomic warfare in the future are frightening. My own feeling was that in being the first to use it, we had adopted an ethical standard common to the barbarians of the Dark Ages. I was not taught to make war in that fashion, and wars cannot be won by destroying women and children. We were the first to have this weapon in our possession, and the first to use it. There is a practical reality that potential enemies will have it in the future and that atomic bombs will sometime be used against us. That is why, as a professional military man with a half-century of service to his government, I come to the end of my war story with an apprehension about the future. These new concepts of "total war" are basically distasteful to the soldier and sailor of my generation. Employment of the atomic bomb in war will take us back in cruelty toward non-combatants to the days of Genghis Khan. It will be a war of pillage and rape of a society, done impersonally by one state against another, whereas in the Dark Ages it was a result of individual greed and terrorism. Thee new and terrible instruments of uncivilized warfare represent a modern type of barbarism not worthy of Christian man. One of the professors associated with the Manhattan Project told me that he had hoped the bomb wouldn't work. I wish that he had been right.