After Iwo Jima and Okinawa, it was clear that Japan had no idea of surrendering and really almost did not do so even after the atomic bombs.
As I said in an earlier post, it was more the declaration of war by Russia then those bombs.
FDR is a war criminal for not using poison gas on the Japanese held Islands—and saving lives of American Soldiers. Clean em like like Vermin rather that frontal assault onto the beach.