That whole 'peace faction' thing has pretty much been debunked since then - particularly now that Japanese internal communications have been made available.

Japan was unlikely to surrender before they did simply because Hirohito (who had militarist leanings himself) was uninterested, and the country was in the grip of militarists.

Yes, there were some attempts at peace talks, but that 'peace faction' was powerless. No connections in the group of militarists running the govt, no connection with Hirohito. There's nothing in the military communications indicating anything else. Yes, MacArthur basically doubled the cost of the Pacific campaign (particularly his insistence that the Philippines be liberated rather than being bypassed) but the US had such an overwhelming advantage in resources that it was successful in spite of his machinations not because of them. IMO FDR should have left him on Corregidor.

The US probably could have successfully invaded Japan - but at a huge cost in lives. The militarists were looking to make it as large a bloodbath as possible. Hirohito did not disagree (and he could have). The US pretty much gave Hokkaido and the Kurils to Stalin to bring Soviet forces in.

So the bombs. I think their major impact was in persuading the emperor to surrender. It wasn't just one terror weapon - it was that the US made it look like we had many and were prepared to keep using them until Japan surrendered - or was decivilized.