As it was, after Hiroshima and Nagasaki, General Tojo’s followers capitulated only through the intervention of the emperor. And it was not altogether clear even then that Japanese fanatics would not attack the Americans as they steamed into Tokyo Bay for the surrender ceremonies.
The radical militarist generals that had taken over control of Japan considered the fire-bombing of Tokyo worse than the a-bombing of Hiroshima. Based on nothing but the death toll they were right. The militarist concluded that the destruction was "tolerable" and that Japan should prepare for an American invasion. If the Emporer had not surrendered via a public radio address the militarist would have never surrendered.
If Saipan and Okinawa are examples of Japanese resistance, and there is no reason to assume otherwise, the destruction of Japan would have been far worse and the number of dead Americans would have been enormous.
But in August 1945 most Americans had a much different take on Hiroshima, a decision that cannot be fathomed without appreciation of the recently concluded Okinawa campaign (April 1-July 2) that had cost 50,000 American casualties and 200,000 Japanese and Okinawa dead. Okinawa saw the worst losses in the history of the U.S. Navy. Over 300 ships were damaged, more than 30 sunk, as about 5,000 sailors perished under a barrage of some 2,000 Kamikaze attacks.
And it was believed at least 10,000 more suicide planes were waiting on Kyushu and Honshu.
The bombing of Hiroshima was horrible but the alternatives were worse beyond comparison.
In some sense, Hiroshima and Nagasaki not only helped to cut short the week-long Soviet invasion of Japanese-held Manchuria (80,000 Japanese soldiers killed, over 8,000 Russian dead), but an even more ambitious incendiary campaign planned by Gen. Curtis LeMay. With the far shorter missions possible from planned new bases in Okinawa and his fleet vastly augmented by more B-29s and the transference from Europe of thousands of idle B-17s and B-24, the ‘mad bomber’ LeMay envisioned burning down the entire urban and industrial landscape of Japan.
Some militarist tried to stop the Emperor from delivering his radio address. Had they succeeded the destruction of Japan would have been complete.