No, it did not save lives. Japan was going to surrender. There was no need for invasion, either. It's on Google, you don't have to look hard. This was done to demonstrate nuclear capabilities to Soviet Union. The US achieved its dishonorable "victory" by burning innocent women and children alive, not by smart military maneuvres or persistence.
Slowly people in this county come to realize that this was an act of terror, unjustified and unforgivable. Ironically, 9/11 helped in that sense. If it's Ok for the US to kill civilians in the most disgusting way why is it not Ok for Bin Laden? He is in a war with us, he gave fair warnings. When it happened people were screaming "He is killing innocent civilians!!!" but very few remembered that the US did much worse atrocity in Japan 50 years back.