General Dwight Eisenhower, after learning of the successful Trinity test, was asked by Stimson for his reaction to their plan for using the atomic bomb against Japan.
" 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 Japanese were ready to surrender and it wasn't necessary to hit them with that awful thing ... I hated to see our country be the first to use such a weapon." -General Dwight Eisenhower Memoirs
The naval blockade and U.S. bombing runs over major
Japanese cities were successful, so Japan had already tried to negotiate peace. Truman ignored Stimson and his other advisers who urged him to
accept a conditional surrender from Japan, allowing Japan to keep their
emperor. Truman said of Japan, “The only language they seem to understand is
the one we have been using to bombard them. When you have to deal with a beast
you have to treat him as a beast."
After Hiroshima, the U.S. Strategic Bombing Survey concluded, "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."
After Hiroshima, the U.S. Strategic Bombing Survey concluded, "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."
"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." - Admiral William Leahy