A ton of folk are talking ignorantly as if the decision to bomb Japan was made in August 1945 and was based on the military situation. That's a bunch of bs. The decision to nuke Japan was made in April/May 1945 by Truman, Stimson and a few of their lackeys and had nothing to do with the military situation. Military wasn't even consulted in the decision.
Here's a quick timeline.
April 12, 1945 - FDR dies. FDR had not yet authorized the dropping of the bombs on Japan, nor had he even informed Truman of the existence of the bomb (which may show how little he trusted Truman's discernment).
April 25, 1945 - Truman has the bombs described to him in detail for the first time, though he'd been informed of their existence two weeks earlier. Rather than consulting his military experts, he immediately sets up a committee to approve the use of the bombs.
April 27, 1945 - Interim Committee convenes for the first time. It is comprised of:
Henry Stimson, Secretary of War
James F. Byrnes, personal representative of Truman and considered the committee's most influential member
George L. Harrison, President of New York Life Insurance
William L. Clayton, businessman and Undersecretary of State
Ralph Bard, Under-secretary of Navy. Bard opposed the committee's decision to drop the bombs and was the only vote against
4 Manhattan Project scientists, who have said they were ignorant about the decision process, knew nothing of the war situation, and felt they were there just to explain the capabilities of the bomb and rubber-stamp whatever decision was made
That's it. That's the whole committee. The people who chose to drop the bomb were basically President Truman, Secretary of War Stimson, and a few businessmen and scientists who just sat there waiting to approve the decision.
May 28, 1945 - In just its 3rd meeting, the Interim Committee approves the final decision of cities to bomb. The main criteria was that the targets would allow the full impact of the bombs to be tested. Thus the targets had to be:
A. Large cities at least 5km in diameter
B. Mostly untouched by bombing, so the full impact of the nuke could be measured
C. Have no mountains or other blockage in the way that would keep the bomb from having maximum destructive impact of surrounding homes
D. Important, but not important enough that they couldn't be ignored for 3 months while the bombs were being finished.
Oh, and there had to be 2 cities targeted because the USA was developing both a Uranium bomb and an Plutonium bomb, with very different mechanisms, and both needed to be tested. That's why Hiroshima and Nagasaki were bombed so quickly right after the other (just 2 days between) without the Japanese government even having time to meet first, but then they didn't mind waiting a week after the 2nd bomb for Japan to surrender. The intention was always to drop both bombs regardless of the military or diplomatic situation.
Once the targets were chosen, the military was instructed to avoid bombing them for the next 3 months so as not to disturb the experiment. After that decision was made, it was never reconsidered and no military leaders were ever consulted to change it. THAT is how and why the bombs were chosen and targeted. It didn't have jack shyt to do with the military situation in August 1945, Truman had made up his mind long earlier, with little deliberation, and didn't even bother talking it through with the people who mattered.
Anyone who claims the decision to drop the bombs was about the situation in August 1945 is ignoring documented reality.
More details about the decision including full notes of the Interim Committee meetings:
ATOMIC BOMB: DECISION (Hiroshima-Nagasaki)