Newer exhibits in Hiroshima have reminded visitors that the city was no random target, but a buzzing manufacturing hub of the Japanese war machine. “Some of us believe that when we think about the bomb, we should think about the war, too,” Hiroshima’s mayor told me in 1994 as we walked through the new exhibit, which Japanese rightists had opposed opening.

Yet even today, 22 years later, the sanitized accounts of the war taught to a new generation of Japanese schoolchildren largely avoid delving into the decision-making that led to the Pacific War, the Rape of Nanjing or questions of whether the “comfort women” were organized by the Japanese military. The vividness of Hiroshima has been melded with anodyne accounts of what preceded it, reinforcing the sense among Americans that, unlike Germany, Japan has never fully grappled with its past.

Many Japanese say the same of the United States. They remember that when the Smithsonian organized the first exhibition of the Enola Gay in 1995, for the 50th anniversary, veterans objected so loudly to the effort to conduct a dispassionate examination of the decision to drop the bomb — and its aftermath — that Congress held hearings and the museum’s director was forced to resign. The exhibition was watered down, and even today — when the famed B-29 can be seen at the Steven F. Udvar-Hazy Center outside Dulles International Airport — any discussion of the short- and long-term horrors of dropping the bomb are cursory, and the history behind it controversial.

“The top American military leaders who fought World War II, much to the surprise of many who are not aware of the record, were quite clear that the atomic bomb was unnecessary, that Japan was on the verge of surrender, and — for many — that the destruction of large numbers of civilians was immoral,” Gar Alperovitz, a leader of the movement to revise the United States’ own historical accounting, wrote last year in The Nation.

Between now and May 27 — when Mr. Obama is to visit the site — the big question will be how views have evolved in both countries since 1995.