We feared that, if the Japanese were told that the bomb would be used on a given locality, they might bring our boys who were prisoners of war to that area. Also, the experts had warned us that the static test which was to take place in New Mexico, even if successful, would not be conclusive proof that a bomb would explode when dropped from an airplane. If we were to warn the Japanese of the new highly destructive weapon in the hope of impressing them and if the bomb then failed to explode, certainly we would have given aid and comfort to the Japanese militarists. Thereafter, the Japanese people probably would not be impressed by any statement we might make in the hope of inducing them to surrender.
In a later television interview he emphasized a more political concern: “The President would have had to take the responsibility of telling the world that we had this atomic bomb and how terrific it was… and if it didn't prove out what would have happened to the way the war went God only knows.”
Someone among the assembled, Ernest Lawrence remembers, concluded that the “number of people that would be killed by the bomb would not be greater in general magnitude than the number already killed in fire raids,” making those slaughters a baseline, as indeed before the awful potential of the new weapon they were.
These troubled men returned to Stimson's office and spent most of the afternoon considering the effect of the bombing on the Japanese and their will to fight. Someone unnamed chose to discredit the atomic bomb's de- structiveness, asserting it “would not be much different from the effect caused by any Air Corps strike of present dimensions.” Oppenheimer defended his creation's pyrotechnics, citing the electromagnetic and nuclear radiation it would expel:
It was probably during this afternoon discussion that Oppenheimer reported an estimate prepared at Los Alamos of how many deaths an atomic bomb exploded over a city might cause. Arthur Compton remembers the number as 20,000, an estimate based on the assumption, he says, that the city's occupants would seek shelter when the air raid began and before the bomb went off. He recalls Stimson bringing up Kyoto then, “a city that must not be bombed.” The Secretary still insisted passionately that “the objective was military damage… not civilian lives.”
The contradiction in Stimson's caveat persisted into his summary of the afternoon's findings, which he offered before he left the meeting at three thirty:
After much discussion concerning various types of targets and the effects to be produced,
Which had been the general formula in Europe, but according to Curtis LeMay the Japanese worked at home, as families:
We were going after military targets. No point in slaughtering civilians for the mere sake of slaughter. Of course there is a pretty thin veneer in Japan, but the veneer was there. It was their system of dispersal of industry. All you had to do was visit one of those targets after we'd roasted it, and see the ruins of a multitude of tiny houses, with a drill press sticking up through the wreckage of every home. The entire population got into the act and worked to make those airplanes or munitions of war… men, women, children. We knew we were going to kill a lot of women and kids when we burned [a] town. Had to be done.
Stimson had now left the meeting. Arthur Compton wanted to talk about problems at the Met Lab. Before that final discussion the spirit of Leo Szilard bustled through the room. Groves had just learned of another round of Szilardian conspiracy. The general was wrathful:
The next morning, June 1, the Interim Committee met with four industrialists. Walter S. Carpenter, the president of Du Pont, estimated that the Soviet Union would need “at least four or five years” to construct a plu- tonium production facility like Hanford. James White, president of Tennessee Eastman, “doubted whether Russia would be able to secure sufficient precision in its equipment to make [an electromagnetic separation plant] possible” at all. George Bucher, the president of Westinghouse, thought that if the Soviets acquired the services of German technicians and scientists they might build an electromagnetic operation in three years. A vice president of Union Carbide, James Rafferty, offered the longest odds: ten years to build a gaseous-diffusion plant from the ground up — but only three years if the Soviets ferreted out barrier technology by espionage.
Mentally Byrnes added processing time to plant construction: “I concluded that any other government would need from seven to ten years, at least, to produce a bomb.” From a political point of view seven years was a millennium.
Stimson still quailed at destroying entire cities with atomic bombs. In the afternoon, absenting himself from the Interim Committee discussions, he distanced that horror by pursuing the precision-bombing question further with Hap Arnold, whom he says he “sternly questioned.” “I told him of my promise from [War Department Undersecretary for Air Robert] Lo-vett that there would be only precision bombing in Japan… I wanted to know what the facts were.” Arnold told Stimson the one about dispersed Japanese industry. Area bombing was the only way to get at all those drill presses. “He told me, however, that they were trying to keep it down as far as possible.” Stimson was willing a few days later to pass that tale along to Truman, with a brace of ambivalent motives thrown in for good measure:
I told him how I was trying to hold the Air Force down to precision bombing but that with the Japanese method of scattering its manufacture it was rather difficult to prevent area bombing. I told him I was anxious about this feature of the war for two reasons: First, because I did not want to have the United States get the reputation for outdoing Hitler in atrocities; and second, I was a little fearful that before we could get ready, the Air Force might have Japan so thoroughly bombed out that the new weapon would not have a fair background to show its strength. He said he understood.
While Stimson was away Byrnes swiftly and decisively co-opted the committee. “Mr. Byrnes felt that it was important there be a final decision on the question of the use of the weapon,” recording secretary Arneson recalled after the war. He described the decision-making process in the minutes he took on June 1:
