Albert Einstein to Linus Pauling:
"I made one great mistake in my life,...when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification - the danger that the Germans would make them.".
"During his(Secreatary of War) recitation of the relevant facts, I had been conscious of a feeling of depression and so 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'. The Secretary was deeply perturbed by my attitude..."
General Douglas MacArthur in conversaion with Norman Cousins (from here):
"When I asked General MacArthur about the decision to drop the bomb, I was surprised to learn he had not even been consulted. What, I asked, would his advice have been? He replied that he saw no military justification for the dropping of the bomb. The war might have ended weeks earlier, he said, if the United States had agreed, as it later did anyway, to the retention of the institution of the emperor."
Robert McNamara(who imo, has no right to talk about this) in the recent documentary 'The Fog of War':
"Why was it necessary to drop the nuclear bomb if LeMay was burning up Japan? And he went on from Tokyo to firebomb other cities. 58% of Yokohama. Yokohama is roughly the size of Cleveland. 58% of Cleveland destroyed. Tokyo is roughly the size of New York. 51% percent of New York destroyed. 99% of the equivalent of Chattanooga, which was Toyama. 40% of the equivalent of Los Angeles, which was Nagoya. This was all done before the dropping of the nuclear bomb, which by the way was dropped by LeMay's command. Proportionality should be a guideline in war. Killing 50% to 90% of the people of 67 Japanese cities and then bombing them with two nuclear bombs is not proportional, in the minds of some people, to the objectives we were trying to achieve."
J.Robert Oppenheimer, after the Trinity test suppposedly said that he was reminded of a quote from Gita:
"If the radiance of a thousand suns
were to burst into the sky,
that would be like
the splendor of the Mighty One—
I am become Death, the shatterer of Worlds"