What would have happened if the atomic bomb wasnt dropped

Trumans reasoning for droping the bomb was so Japan would surrender; but many people at this time believed that Japan would have surrendered without the atomic bomb. No one can really ever figure out what would have happened if we didn't drop the atomic bomb but one thing we do know is; the arms race would not have started and the world would be completly diffrent today. Would Japan have ever backed down that is something we will never know