“Even without the atomic bombing attacks,” concluded the United States Strategic Bombing Survey of 1946, “air supremacy over Japan could have exerted sufficient pressure to bring about unconditional surrender and obviate the need for invasion. “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 … Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war [against Japan] and even if no invasion had been planned or contemplated.”
The National Archives in Washington contains documented Japanese peace overtures as early as 1943. None was pursued. A cable sent on May 5, 1945 by the German ambassador in Tokyo and intercepted by the U.S. made clear the Japanese were desperate to sue for peace, including “capitulation even if the terms were hard”. Nothing was done.
The U.S. Secretary of War, Henry Stimson, told President Truman he was “fearful” that the U.S. Air Force would have Japan so “bombed out” that the new weapon would not be able “to show its strength”. Stimson later admitted that “no effort was made, and none was seriously considered, to achieve surrender merely in order not to have to use the [atomic] bomb”.
Stimson’s foreign policy colleagues — looking ahead to the post-war era they were then shaping “in our image”, as Cold War planner George Kennan famously put it — made clear they were eager “to browbeat the Russians with the [atomic] bomb held rather ostentatiously on our hip”. General Leslie Groves, director of the Manhattan Project that made the atomic bomb, testified: “There was never any illusion on my part that Russia was our enemy, and that the project was conducted on that basis.”