What if Nuclear weapons had never been developed?
If perhaps somehow there was not enough fissile matierial on earth, or certain scientists such as planck, einstein, oppenheimer were never born or perhaps oppenheimer falsifies his work out of terror as to what might occur, and this somehow creates a scientific orthodoxy that is waiting to be challenged.
Either way the USA does not develop the bomb, and is faced with somehow forcing a fanatical Japan to surrender. Will they in this reality attempt a land invasion? Will they simply blockade her and firebomb her cities? How much longer will the war continue for?
There will be no umbrella of peace, no mutally assured destruction, so what form will the third and indeed fourth and maybe fifth world wars take?