At a press conference in Tokyo today, a Japanese reporter asked Obama whether Harry Truman made "the right decision" to drop nuclear weapons on Hiroshima and Nagasaki. Obama dodged the question (easy to do because it was a multi-parter. Note to reporters: Multi-part questions usually ensure non-answers to the toughest bits). I wonder what he really thinks. It seems likely that, like the overwhelming majority of Americans, Obama thinks the bombs had to be used. And that's not really a sentiment you want to be expressing at a press conference in Tokyo with the Japanese prime minister.
But given his longstanding views about nuclear weapons, I'm actually not certain that Obama agrees with the decision. And I can also imagine him thinking that Hiroshima was the right and necessary thing. But also that Nagasaki--which as I understand it was bombed when serious talks about surrender were already underway within Japan--may have been gratuitous. (A view apparently shared by Dwight Eisenhower, if this source is reliable.)
Not that we'd be very likely to hear that from him, either.