When President Barack Obama tours Hiroshima’s haunting relics of nuclear warfare, he will be making a trip that past administrations weighed and avoided. For good reason: The hollowed core of the city’s A-Bomb Dome and old photos of charred children are sure to rekindle questions of guilt and penitence for World War II’s gruesome brutality.

Obama’s visit later this month already is stirring debate on both sides of the Pacific about the motivations and justifications for the nuclear attacks in Hiroshima and Nagasaki. Anything he says will be sharply scrutinized in the U.S., Japan and beyond. Anything resembling an apology could become a wedge issue in the U.S. presidential campaign and plunge Obama into the complicated politics of victimhood among Japan and its Asian neighbors.

“I don’t have any problem with him going, but there is nothing to apologize for,” said Lester Tenney, a 95-year-old American survivor of the 1942 Bataan Death March, when the Japanese marched tens of thousands of Filipino and U.S. soldiers to prison camps, and hundreds to their deaths.

Forty-two years ago, a White House aide suggested President Gerald Ford visit the city where 140,000 people were killed in the inferno on Aug. 6, 1945. A senior adviser, Gen. Brent Scowcroft, vetoed the idea: “It could rekindle old animosities in Japan at a time when we are striving for new relationships.”

Asked in 2008 if he might go, President George W. Bush was noncommittal. In the end, it took 65 years for a U.S. ambassador to attend the city’s annual memorial service. Secretary of State John Kerry traveled there last month.

Obama won’t say sorry, U.S. officials have emphasized repeatedly since announcing the trip. Instead of revisiting the fateful decision to drop the bombs, the president will “shine a spotlight on the tremendous and devastating human toll of war” and “honor the memory of all innocents who were lost,” said Ben Rhodes, Obama’s deputy national security adviser.

In some ways, Obama has it easier than his predecessors. Japanese survivors, known as “hibakusha,” have long refrained from demanding an apology, seeking to mobilize Hiroshima’s revered sites for the causes of pacifism and denuclearization. Even if Obama’s effort to reduce America’s arsenal has stalled, most Japanese support his much-recited preference for a nuclear-free world and last year’s arms-control deal with Iran.

Nevertheless, Ian Buruma, a professor at Bard College and author of “Year Zero: A History of 1945,” said visiting Hiroshima is risky because of the lack of consensus in the U.S. or Japan about the bombings.

Many Japanese see the attacks as atrocities; others view them as punishment for Japan’s hostile acts, which included conquering much of Asia and launching the sneak attack on Pearl Harbor on Dec. 7, 1941, that led the U.S. into the war. And in the U.S., too, the debate rages 71 years after “Little Boy” and “Fat Man” fell from the sky.

A majority of Americans justify the bombings for hastening the war’s end. Historians are split. Buruma said camps include those who believe President Harry Truman, barely sworn in, failed to stop “bureaucratic momentum” toward using a weapon that took so long to develop. Others argue U.S. leadership mainly wanted to intimidate the Soviet Union.

“I don’t think there will ever be clarity,” he said.

Japan’s debate often has made it hard for U.S. presidents to visit, Buruma said.

Nationalists put forward the idea that the atomic bombs “evened out” Nazi-allied Japan’s wartime atrocities, he said. The war in the Pacific killed millions across Asia, including perhaps 14 million Chinese, and Japan was responsible for chemical weapons attacks, widespread torture, forced labor and sexual slavery. American deaths topped 100,000; a quarter-million were wounded.

Meanwhile, left-wing Japanese groups sought to incorporate Hiroshima into their propaganda of Soviets and communists as forces for peace, and the Americans as warmongering imperialists, Buruma said.

With time, however, these movements largely receded as the U.S.-Japanese alliance matured.