The visit by Japan’s prime minister, Shinzo Abe, to the United States next week is important on several levels. He will be the first Japanese leader to address a joint meeting of Congress. He and President Obama are expected to announce progress on a key issue, increased defense cooperation, and possibly on a second, trade. They will also discuss a third challenge, China’s growing influence in Asia.

The context is also important: This year is the 70th anniversary of Japan’s defeat in World War II, and to some extent the visit is intended as a celebration of the country’s remarkable postwar resurrection and its robust alliance with an old enemy, which has become a foundation of regional stability.

But the success of the visit also depends on whether and how honestly Mr. Abe confronts Japan’s wartime history, including its decision to wage war, its brutal occupation of China and Korea, its atrocities and its enslavement of thousands of women forced to work as sex slaves or “comfort women” in wartime brothels.

By now, that history should have been settled. That it is not settled is largely the fault of Mr. Abe and his right-wing political allies who keep questioning history and even trying to rewrite it, stoking regional tensions. Mr. Abe may have more to say on all this on Aug. 15, the actual date of the surrender. But his remarks to Congress will send an important signal.

Mr. Abe’s nationalist views and pressure from competing political forces have affected his judgment on these delicate issues. He has publicly expressed remorse for the war and said he will honor Japan’s past apologies for its aggression, including the sex slavery. Yet he has added vague qualifiers to his comments, creating suspicions that he doesn’t take the apologies seriously and will try to water them down.

His government has compounded the problem by trying to whitewash that history. This month, South Korea and China criticized efforts by Japan’s Education Ministry to force publishers of middle-school textbooks to recast descriptions of historical events — including the ownership of disputed islands and war crimes — to conform to the government’s official, less forthright analysis. And last year, the Abe government tried unsuccessfully to get the United Nations to revise a 1996 human rights report on the women Japan forced into sex slavery.

Many Japanese right-wingers believe their country was wrongly maligned by America and its allies after the war. Mr. Abe has given the impression that he believes Japan has already done enough to make amends for its militarism and atrocities. He says he prefers to get on with more firmly establishing his country as a 21st-century leader that can help the United States counter China in Asia and take on other global responsibilities.

But Japan cannot credibly fill that broader role if it seeks to repudiate criticism of its past. Emperor Akihito of Japan and his family have set a much better example; in an apparent rebuke of Mr. Abe, Crown Prince Naruhito has been outspoken about the need to “correctly pass down history” to future generations.

Much good can come from the Washington meeting if Mr. Abe and Mr. Obama give final approval to the first new guidelines in 17 years for expanded American-Japanese defense cooperation and make substantial progress on a new trans-Pacific trade agreement. A lot will depend on whether Mr. Abe is willing to push aside his right-wing supporters and set a tone that can strengthen stability in Asia, rather than weakening it.