Nagasaki accomplished the realization by the Japanese government that they could no longer insist on their list of unacceptable conditions for surrender.
The traditional claim that Japan refused to surrender after Hiroshima is not true. The claim that the bombing of nagasaki was gratuitous is not true.
neither did the firebombing of Tokyo,
The firebombing of Tokyo is what started the Japanese government discussing the topic of surrender "with honor" in the first place.
the bombing of Dresden,
While the level of carnage that actually occurred at Dresden was completely unforeseen, the original stated objective of the Dresden bombing did accomplish its goal: to disrupt the Nazis' efforts to reinforce their Eastern Front and prevent the Soviet Belorussian Front and Ukrainian Front from linking up.
nor Sherman’s march to the sea.
The purpose of the March was twofold: (1) to demonstrate to the people of the Confederacy that Union armies could operate at will in their heartland and that their own armed forces could not defend them and (2) to isolate Lee from Johnston. Both missions accomplished.
The only "unacceptable" condition that was left at that point remained keeping the emperor, which Truman finally agreed to after Nagasaki....despite his earlier refusal to accept this condition. I can't understand why so many here are willing to accept the INTENTIONAL use of terror (e.g. killing of thousands of innnocents including babies in the crib) as a legitimate method of war. We prosecuted people for war crimes who did a lot less.
Well, it was also intended to destroy the South's ability to wage war, by destroying property rather than killing people. This was a laudable goal, the people who starved due to the destruction of property notwithstanding.