Tomorrow will mark the anniversary of one of the most morally contentious events of the 20th century, the atomic bombing of Hiroshima. And after 58 years, there's an emerging consensus: we Americans have blood on our hands.

There has been a chorus here and abroad that the U.S. has little moral standing on the issue of weapons of mass destruction because we were the first to use the atomic bomb. As Nelson Mandela said of Americans in a speech on Jan. 31, ''Because they decided to kill innocent people in Japan, who are still suffering from that, who are they now to pretend that they are the policeman of the world?''

The traditional American position, that our intention in dropping the bombs on Hiroshima and then Nagasaki was to end the war early and save lives, has been poked full of holes. Revisionist historians like Gar Alperovitz argue persuasively that Washington believed the bombing militarily unnecessary (except to establish American primacy in the postwar order) because, as the U.S. Strategic Bombing Survey put it in 1946, ''in all probability'' Japan would have surrendered even without the atomic bombs.

Yet this emerging consensus is, I think, profoundly mistaken.

While American scholarship has undercut the U.S. moral position, Japanese historical research has bolstered it. The Japanese scholarship, by historians like Sadao Asada of Doshisha University in Kyoto, notes that Japanese wartime leaders who favored surrender saw their salvation in the atomic bombing. The Japanese military was steadfastly refusing to give up, so the peace faction seized upon the bombing as a new argument to force surrender.