There's a guy named Joseph Grew, a former US ambassador to japan before WW2 who tried to stop the bombings. Basically he put forth the argument that Japan would

There's a guy named Joseph Grew, a former US ambassador to japan before WW2 who tried to stop the bombings. Basically he put forth the argument that Japan would be willing to surrender as long as the emperor could keep his title/powers/etc. Truman removed this provision at the last minute, and surprise the surrender was not accepted. In the end we proceeded to use the nukes, and then let the emperor keep his title anyway. It's interesting that I never heard of him until watching a documentary about this while in Japan.