the BBC documentary last night on the "bomb" clearly stated the view that the Hiroshima bomb was dropped to demonstrate the fire power of the Allies because the war had no sight of any conclusion and was not going well for the Allies. Many military and civilian deaths on both sides would inevitably be involved with a continuation of the war, plus casualties.
The programme - involving many of those wot were there - stated that Japan was invited to surrender after Hiroshima and didn't. Some of the Manhattan Project wanted to demonstrate the bomb to frighten Japan into surrender.
After Nagasaki (tertiary target chosen due to the weather) the Emperor intervened and told the government/military to surrender.

Japan may have been suing for a negotiated settlement, diplomats make these noises, it can be a military tactic to weaken the resolve of the opposition. But how genuine or strong were the voices?

History is made by the winners, and those that weren't there at the time are in a better position to win that fight! History is indeed bunk, there are those trying to bunk it up!

The programme is on iPlayer for those wanting more clarity on the subject