"What we must understand is that the industries, processes, and inventions created by modern science can be used either to subjugate or liberate. The choice is up to us" ~ Henry A. Wallace, 33rd US President
27th, December, 1945 - President Wallace authorises the use of atomic weaponsin 1945, the disastrous casualty count since X-Day forced President Wallace to authorise General MacArthur's request to make use of the atomic bomb for Operation Coronet. This, the second phase of the invasion of the Japanese homelands, had anticipated an even bigger amphibious landing of up to forty divisions south of the capital on Y-Day, 1st March, 1946.
Put simply, the math didn't work -
the multiplication of the same casualty county with a much larger force was intolerable. And so despite his great reluctance he had been forced to swallow his own words narrated in the 1942 propaganda movie The Price of Victory. This moral climb-down was because the bloodbath in Kyushu had transformed the nature of the war. Although Chief of Staff George Marshall had advocated the early use of the bomb since V.E. Day, both theatre command Macarthur and Wallace had been firmly against it - but for different reasons. If not for the civilian death count projection Wallace would have have favoured a blockade and initially saw the bomb as unconscionable. Macarthur as a game-changer in ways no one could foresee.
His moral compass had performed a complete 360. The Soviets had landed Hokkaido and of course suffered much the same. Somewhat naively Wallace had seen strategic value for post-war relations in a joint victory in Japan and one of many strategic objections to the bomb was its unilateral use. As events were to transpire, Wallace would face a whole series of such challenges to his better nature. Eastern European countries would refuse the generous offer of his Wallace Plan, former Grand Alliance partners quarrelled over the government of the defeated nations of Germany and Japan, Communism was on the march relentlessly and the economy failing to grow. And so for the first time since 1920 it looked likely that an incumbent President would be denied the nomination by his own party which to be honest had only reluctantly swung in behind the late FDR's "Wallace or bust" strategy.
Author's Note: in reality [reports Wikipedia] the President and several of his confidantes wanted to replace Wallace with someone more acceptable to Democratic Party leaders and Roosevelt's advisors, knowing that Roosevelt might not live out a fourth term.