The following summary by Alex Wellerstein represents his understanding of the consensus view. Notably the idea that the bombings where carefully motivated by some sort of ethical calculus is not something that historians now believe. From
http://blog.nuclearsecrecy.com/2013/03/08/the-decision-to-us...* It’s not really clear that Truman ever made much of a “decision,” or regarded the bomb/invasion issue as being mutually exclusive. Truman didn’t know if the bomb would end the war; he hoped, but he didn’t know, couldn’t know. The US was still planning to invade in November 1945. They were planning to drop as many atomic bombs as necessary. There is no contemporary evidence that suggests Truman was ever told that the causalities would be X if the bomb was dropped, and Y if it was not. There is no evidence that, prior to the bombings of Hiroshima and Nagasaki, that Truman was particularly concerned with Japanese causalities, radiation effects, or whether the bombs were ethical or not. The entire framing of the issue is ahistorical, after-the-fact, here. It was war; Truman had atomic bombs; it was taken for granted, at that point, that they were going to be used.
* Defeat is not surrender. Japan was certainly defeated by August 1945, in the sense that there was no way for them to win; the US knew that. But they hadn’t surrendered, and the peace balloons they had put out would have assumed not that the Emperor would have stayed on as some sort of benign constitutional monarch (much less a symbolic monarch), but would still be the god-head of the entire Japanese country, and still preserve the overall Japanese state. This was unacceptable to the US, and arguably not for bad reasons. Japanese sources show that the Japanese military was willing to bleed out the country to exact this sort of concession from the US.
* American sources show that the primary reason for using the bomb was to aid in the war against Japan. However, the fact that such weapons would be important in the postwar period, in particular vis-à-vis the USSR, was not lost on American policymakers. It is fair to say that there were multiple motivations for dropping the bomb, and specifically that it looks like there was a primary motivation (end the war) and many other “derivative” benefits that came from that (postwar power).
* Japanese sources, especially those unearthed and written about by Tsuyoshi Hasegawa, make it clear that prior to the use of the atomic bombs, the Japanese cabinet was still planning on fighting a long battle against invasion, that they were hoping to exact the aforementioned concessions from the United States, and that they were aware (and did not care) that such an approach would cost the lives of huge numbers of Japanese civilians. It is also clear that the two atomic bombs did shock them immensely, and did help break the stalemate in the cabinet — but that the Soviet invasion of Manchuria also shocked them immensely, perhaps equally, maybe even more (if you have a choice between being occupied by Truman or occupied by Stalin, the decision is an easy one). But there is no easy way to disentangle the effects of the bombs or the Soviet invasion, in this sense — they were both immensely influential on the final decision. That being said, using the bomb as an “excuse” (as opposed to “we are afraid of Russians”) did play well with the Japanese public and made surrender appear to be a sensible, viable option in a culture where surrender was seen as a complete loss of honour.