Memoirs by Harry S. Truman, Harry S. Truman, Vol 1, Year of Decisions, pages 417, 419
General Marshall told me [Harry S. Truman] that it might cost a half a million American lives to force the enemy’s surrender on his home grounds.”
It was the recommendation [of the committee of scientists, government officials, and university scholars] that the bomb be used against the enemy as soon as it could be done. They recommended further that it should be used without specific warning and against a target that would clearly show its devastating strength. I had realized, of course, that an atomic bomb explosion would inflict damage and casualties beyond imagination. On the other hand, the scientific advisors of the committee reported, ‘We can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use.’ It was their conclusion that no technical demonstration they might propose, such as over a deserted island, would be likely to bring the war to an end. It had to be used against an enemy target.”
George Marshall, Forrest Pogue, Volume 4, Statesman 1945-1959, pages 24-25
“[George Marshall] strongly doubted that Japan could be defeated without an invasion of the home islands. His view was reinforced by the virulence of the kamikaze attacks and by the suicidal resistance of the Japanese at Iwo Jima and Okinawa. He was unpersuaded by Air Force and Navy arguments that Japan could be quickly strangled to death by the bombing of its cities and attacks on its shipping. He thought these tactics might prolong the war for at least a year and that the bulk of the mop-up fighting would still fall heaviest on the Army, and that public opinion would not accept the continuing casualties, which would begin to seem endless. So he resumed his urging that the Soviet Union be brought into the war to place maximum pressure on Japan, and he wanted to use the atomic bomb, if a test provide it effective, to shock the enemy into surrender without resorting to an invasion that could only be bloody.
The United States had taken up the business of splitting the atom to forestall Germany getting a weapon from it first. Now the main idea was to shorten the war. As far as Marshall was concerned, he went to Potsdam with his mind set on using the bomb to reduce casualties . . .
Close scrutiny of Marshall’s role in the development of the bomb shows that he saw it as a weapon to wind up the war swiftly and thus effect enormous reduction in casualties.”
The Second World War, Winston Churchill, Volume 6, Triumph and Tragedy, page 545
“Up to this moment [July 17, 1945] we [British and Americans] had shaped our ideas towards an assault upon the homeland of Japan by terrific air bombarding and by the invasion of very large armies. We had contemplated the desperate resistance of Japanese fighting to the death with Samurai devotion, not only in pitched battles, but in every cave and dug-out. I had in my mind the spectacle of Okinawa Island, where many thousands of Japanese, rather than surrender, had drawn up in line and destroyed themselves by hand grenades after their leaders and performed the solemn rite of hari-kari. To quell the Japanese resistance man by man and conquer the country yard by yard might require the loss of a million American lives and half that number of British—or more if we could get them there: for we were resolved to share the agony. Now all this nightmare picture had vanished. In its place was the vision—fair and bright indeed it seemed—of the end of the war in one or two violent shocks. I thought immediately myself of how the Japanese people, whose courage I had always admired, might find in the apparition of this almost supernatural weapon and excuse that would save their honour and release them from their obligation of being killed to their last fighting man.”