It's not contentious. The facts are clear. It took an extraordinary turnabout by the Emperor to even consider surrender, and that only happened after the two bombs. Before the bombs the Japanese leaders believed they could force the US to accept a peace where they kept most of the lands they had enslaved.

The bombings of Nagasaki and Hiroshima weren't even the most deadly of the war. The US had burned most of Tokyo to the ground and more was coming.

Japanese citizens were going to die in masses when the invasion force hit the beach. Either sacrificing themselves in suicide attacks, or being used as human shields.