My father was in the US Army during WW2 and involved in two amphibious landings on Japanese held islands. Yes, he landed with Marines, but the Army was still there.
He saw first hand the horror that was island warfare in the Pacific. He felt that he might not have survived a landing on mainland Japan.
From what I have read, the Japanese military did not want the Emperor to surrender. It took dramatic events, such as the invasion by Russia and the Atomic bombs to pull the rug out from under the military opposing surrender.
There was a very interesting book I read about psychological warfare in the Pacific during WW2. https://www.abebooks.com/book-search/title/you-can‘t-fight-tanks-with-bayonets/
The full title of the book is “You Can't Fight Tanks with Bayonets: Psychological Warfare against the Japanese Army in the Southwest Pacific (Studies in War, Society, and the Military)
The Japanese military leadership was consistently lying to the Japanese soldier and mentally conditioning him to die for the emperor. It took really harsh images to cause the typical soldier to say, wait a minute this is not going to work and is stupid. The most successful image used by the US military was of a Japanese solder without ammunition, without explosives charging a USA tank with a bayonet. The outcome of such stupidity was obvious. On many islands that is what the typical Japanese solider who have no supplies was looking at. The atomic bombs provided those not in the Japanese military leadership with a wake-up call that the war was hopeless; that Americans could destroy every city in Japan with one bomb and Japan could do nothing to stop them.
The Atomic bombs were necessary as a way of providing everyone with something unexpected to point to as saying the war was over. The firebombing of Tokyo and other cities was much more of an uncivilized event than the dropping of two atomic bombs.
Continued firebombing, atomic bombing of other cities, starvation by sea blockage prior to a land invasion would have caused so much death and suffering. This says nothing of those who would have died in the land warfare on the Japanese home islands. The people who died in the two atomic bombs were sacrificed to end the war quickly and to save countless lives.
“From what I have read, the Japanese military did not want the Emperor to surrender.”
It was not up to the emperor to surrender. It was up to the advice of those advising him. They couldnt agree, so he ordered them to agree. There was a coup attempt to stop the recording from being played-yes they recorded it because no common person was allowed to hear his voice. They also were never allowed to look at him. He was a God on earth to them.
A real culture shock happened after.
Basically.