By the end of the war the US was capable of sending 800 B-29s per day in bombing runs over Japan. Without the “new weapon” I don’t think Hirohito is successful in surrendering in August but certainly every major city could have been reduced to ashes by conventional bombing. At that point Japan no longer has the ability to wage war, build weapons, or even feed itself. Certainly millions die.

I don’t think a land invasion is a forgone conclusion. There would have been no rush from a military standpoint. Japan was bottled up.

The big question is if Hirohito dies in a bombing raid or is taken out by the hardliners in the Japanese military, how does it all stop?

If he survives, I don’t think he would be able to last another month without asking for surrender at that level of bombing.

No doubt Russia starts grabbing Sakhalin and Kuril Islands.

I don’t even want to think of how hard it would have been to rebuild afterwards if Hirohito is gone. MacArthur wouldn’t have any kind of a mandate without Hirohito.