You assume that those two bombings had an effect or sped up the surrender. They provingly did not. The decision was made to show a) force to USSR and the rest o

You assume that those two bombings had an effect or sped up the surrender. They provingly did not. The decision was made to show a) force to USSR and the rest of the world b) explain the funds spent on creating nuclear weapons. They had been firebombing and eradicating whole Japanese cities for days/weeks. (Another topic to discuss -- that the pressure was applied to the civilian non-fighting population, regardless of the method.) The late Japanese surrender is a failure of diplomacy -- the two sides could not communicate and neither side could swallow the whole "emperor question." When the Russians started moving and declared war to Japan, both sides gave up something: "unconditional" surrender and emperor got to stay and not implicated in anything related to the war. See the whole background behind the following trials, where a lot of people either did not get prosecuted or chose to die instead of implicating the emperor in any way.