As a followup to the causes of the Japanese surrender, here is a talk given by Freeman Dyson, where, starting at 9:40, he makes the case that the Japanese surrender was not because of the bombs, but rather was motivated by fear of Russian occupation of the Japanese homeland. Dyson goes on to say that Hirohito "didn't mention the bombs at all", but made reference to Emperor Meiji's acceptance of surrender by Japanese troops in Manchuria in 1895.
Well, I looked up Hirohito's surrender speech, and not only DOES he mention the bombs, he makes no mention of Meiji at all. The most that can be said of fear of Russian occupation is perhaps an oblique reference that "the general trends of the world have all turned against her [Japan's] interest."
As for the bombs, Hirohito explicitly said in his broadcast,
"Moreover, the enemy has begun to employ a new and most cruel bomb, the power of which to do damage is, indeed, incalculable, taking the toll of many innocent lives. Should we continue to fight, it would not only result in an ultimate collapse and obliteration of the Japanese nation, but also it would lead to the total extinction of human civilization.
Such being the case, how are we to save the millions of our subjects, or to atone ourselves before the hallowed spirits of our Imperial Ancestors? This is the reason why we have ordered the acceptance of the provisions of the joint declaration of the powers."
https://pearlharborwarbirds.com/japanese-surrender-speech-emperor-hirohito/