Once again you show you have no understanding of war.
Surrender was not imminent. Until the bombs Japan was still operating under a strategy of trying to make final victory so bloody and expensive that we would give up and leave them alone. That's what the "peace" offers were about.
You're still committing the fundamental liberal fallacy of thinking there is a good answer. Those who subscribe to this are very likely to make incredibly bad decisions when faced with a situation where there is no good answer.
In the real world you're often forced to choose the lesser evil.
The Japanese did want to surrender some months earlier as history shows. As you mentioned the Cities were being constantly bombed for the allies had control over land sea and air. A ceasefire was possible so that peace talks could begin. As clearly mentioned earlier, even with the unconditional surrender of Japan the allies soon backed down on removing Hirohito and ceased the pursuit of Japanese war criminals.
Therefore the ceasefire for peace talks was more a common sense action than a lesser evil.
Sun Tzu also stated: In the practical art of war, the best thing of all is to take the enemy's country whole and intact; to shatter and destroy it is not so good. So, too, it is better to recapture an army entire than to destroy it, to capture a regiment, a detachment or a company entire than to destroy them.
You don't seem to be able to understand the difference between ending the war without surrender and surrender.
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This^^^
In the first place Truman as C in C would have been derelict in his duty to the soldiers, sailors and airmen if he didn't use the bombs and instead went on with the invasion. Military planners estimated a million US casualties and up to 100,000 deaths on our side and well over a million more Japanese deaths. What our planners did not realize was that the Japanese had been husbanding their aircraft and aviation fuel and had over 100,000 aircraft that were to be used as kamikazes against our invasion fleet. They were also training their civilians in combat using spears made of sticks.
To blame the US for it's tactics to end the war is asinine, almost as asinine as the Japanese decision to start a war against two major world powers when she was struggling in her war with a weak nation (China). People forget that the Japanese started the war and they started it for imperial purposes.
America has continued its involvement of its asininities into the 21st Century while sending troops to die in Vietnam and Iraq while also getting involved in Libya and Syria to name a few. At the same time it has racked up debts exceeding a trillion dollars.
If peace talks had occurred a few months earlier as the Japanese requested, then even more lives would have been saved. The Japanese had no place to go. The US wanted unconditional surrender but actually did not achieve this in the end. Hirohito and most war criminals were not prosecuted.
If there was a ceasefire earlier with Japan in response to its request for peace, then not only would the deaths have been avoided but the thousands of Koreans, Chinese and allied prisoners who were in Nagasaki would not have been killed. There again the US is known for killing its own troops or those of its allies through friendly fire.
Of course the Japanese were training its population for defence of the Islands. This is what Britain did when threatened by Germany and is known as common practice in war.
The UK didn't train schoolkids as suicide bombers.