Japanese soldiers had started to surrender on Okinawa. Also, there was plenty of political intrigue going on. I think an invasion would have toppled the government. But that’s just my opinion. After Fat Man, we were fresh out of nukes. I think we didn’t have any more until February 1946. But it was necessary to end the war befoer the Soviets got involved and ruined everything. Actually, I think the only thing the Japanese were afraid of was the Russians.