What I'm saying is the Soviet entry into the war by itself was enough to push Japan into an (almost) unconditional surrender to the US, so the bombings were unn

What I'm saying is the Soviet entry into the war by itself was enough to push Japan into an (almost) unconditional surrender to the US, so the bombings were unnecessary. The timing was not coincidental, they had agreed on a Soviet entry within three months of V-day in Europe at Yalta. While Stalin probably didn't know about the bombing, Truman almost certainly knew the specific date of the invasion of Manchuria in advance and it likely established the timetable.