This is significant because at the Yalta conference in February 1945, the USSR promised to declare war against Japan within three months of the defeat of the Germans, the delay being required to remobilize to the new eastern front. Truman knew the August 8 Soviet invasion was coming when deciding whether to use the Bomb. The obvious conclusion is that we did it not to shorten the war but to make sure that the Japanese surrender was to the US, and thus reduce the Soviet influence in east Asia.
Today's news is predictably full of hand-wringing. I just wish any of the articles would mention Yalta.