I still hate this time of year. Though the post and comments are of generally high quality, and the introduction of actual Japanese scholars and sources into the debate is welcome, I still haven’t seen anyone address the “sufficient ≠ necessary” issue to my satisfaction. There’s an awful lot of post hoc ergo propter hoc in the discussion, as well as an awful lot of “plausible, therefore true” fallacies on the other side.
It’s really one of the nastiest questions of historical causality: there’s counterfactuals, personality/psychological considerations, cultural considerations, long-term strategic and moral implications, the inevitability trap, and self-justification and distortion in the sources on all sides, not to mention huge gaps in the record on critical persons and times. The problem, really, is to approach it the way we do every other historical question, because to treat it as a sui generis issue (which it really looks like) can lead to the use of arguments and methods which are unacceptable in other contexts (and should be unacceptable in this one).
Like Eric Rauchway, I rarely spend a lot of time on the atomic bombings in either my World History or Japanese history courses, partially because, like him, I put it in the context of the general escalation of air war and military technology (a theme that runs through my World courses in particular) and partially because the debate is driven more by ethical than by historical questions. Otherwise we would have moved on ages ago, because the consensus position of Japanese historians reached almost a half century ago still largely stands: The combined shock of the atomic bombs and Soviet entry pushed the Japanese cabinet to the point where they could accept the unconditional end of the war, but things happened so fast that there’s really no way to tell whether one or the other would have been sufficient in isolation, nor can we know for sure whether a conditional surrender could have been reached earlier because nobody tried very hard.