"War is cruelty and you cannot refine it, the crueler we make it, the shorter it will be. - William T. Sherman, 1864.
A couple of academic double-domes cooked up the idea but it never went anywhere beyond the water cooler. Post-war, when the Soviets wanted us to be the bad guys, these same chin-pullers were held up as examples of what we should have done.
You have to understand, this was total war. Japanese soldiers not only fought to the death, they committed suicide to keep from being captured. Japanese civilians were of the same mind-set. They had been taught from birth that dying for the Emperor was the highest calling for a Japanese citizen. Japan was not going to quit until the Emperor gave them permission to. Blowing up a few trees wasn't going to get that done. Hell's fire, there was doubt that killing cities with the things was going to do it. After all, 750,000 had died IN ONE NIGHT during a fire bombing attack on Tokyo and a town called Toyama (roughly the size of Knoxville) was 99.6% burned out during a similar raid a few months later.
What shocked the Japanese Emperor was that while the fire raids used 200-300 B-29s, the nuclear missions required but one. He knew we had a lot of bombers and more were on the way.
As soon as word leaked out that Hirohito was going to broadcast his decision to surrender, certain Army officers became convinced that the Emperor had been duped or had agreed under duress and that it was their duty to rise up and free him to resume command of the nation and continue the war to victory. For loyal Japanese, surrender was not only unbearable, it was unthinkable.
The conspirators finalized their plans and focused on preventing the broadcast of the Emperors message to his people scheduled for August 14. In the end, their plot was foiled, in large part because of the last B-29 bombing mission carried out the night of August 13-14 which caused a nation-wide blackout and communications shutdown. Unable to communicate effectively, the conspirators failed. Many committed seppuku afterward. The Emperors broadcast went ahead on the 14th.
It was that close.
With respect to the fatality estimate of 750,000, are you referring to the mission on 910 March ("Operation Meetinghouse") that involved "334 B-29s [which] took off to raid with 279 of them dropping 1,665 tons of bombs on Tokyo"? If so, what is the source for an estimate of 750,000 deaths? I ran across the following projections for that raid:
"The US Strategic Bombing Survey later estimated that nearly 88,000 people died in this one raid, 41,000 were injured, and over a million residents lost their homes. The Tokyo Fire Department estimated a higher toll: 97,000 killed and 125,000 wounded. The Tokyo Metropolitan Police Department established a figure of 83,793 dead and 40,918 wounded and 286,358 buildings and homes destroyed. Historian Richard Rhodes put deaths at over 100,000, injuries at a million and homeless residents at a million. These casualty and damage figures could be low; Mark Selden wrote in Japan Focus:
The figure of roughly 100,000 deaths, provided by Japanese and American authorities, both of whom may have had reasons of their own for minimizing the death toll, seems to be arguably low in light of population density, wind conditions, and survivors' accounts. With an average of 103,000 inhabitants per square mile (396 people per hectare) and peak levels as high as 135,000 per square mile (521 people per hectare), the highest density of any industrial city in the world, and with firefighting measures ludicrously inadequate to the task, 15.8 square miles (41 km2) of Tokyo were destroyed on a night when fierce winds whipped the flames and walls of fire blocked tens of thousands fleeing for their lives. An estimated 1.5 million people lived in the burned out areas.
In his 1968 book, reprinted in 1990, historian Gabriel Kolko cited a figure of 125,000 deaths. Elise K. Tipton, professor of Japan studies, arrived at a rough range of 75,000 to 200,000 deaths. Donald L. Miller, citing Knox Burger, stated that there were "at least 100,000" Japanese deaths and "about one million" injured" (
https://en.wikipedia.org/wiki/Bombing_of_Tokyo).
Citations for references cited above are:
Selden, Mark (May 2, 2007). "A Forgotten Holocaust: US Bombing Strategy, the Destruction of Japanese Cities & the American Way of War from World War II to Iraq".
Japan Focus.
Rhodes, Richard.
The Making of the Atomic Bomb. p 599. Simon & Schuster Paperbacks (1984).
Kolko, Gabriel (1990) [1968].
The Politics of War: The World and United States Foreign Policy, 19431945. pp. 53940.
Tipton, Elise K. (2002).
Modern Japan: A Social and Political History. Routledge. p. 141.
Miller, Donald L.; Commager, Henry Steele (2001).
The Story of World War II. New York: Simon and Schuster. p. 456.