The White House announced Tuesday that Barack Obama will become the first sitting American president to visit Hiroshima, where the United States dropped an atomic bomb on August 6, 1945, to force Japan’s surrender in World War II.

Obama will follow two of his predecessors to Hiroshima’s Peace Memorial Park, but neither was in office at the time of their visits: Jimmy Carter visited on May 5, 1984, long after he’d left the White House, and Richard Nixon went on April 11, 1964, four years before he won the presidential election.

Carter, who visited the memorial with his wife, Rosalyn, and their daughter, Amy, pledged at the time to “eliminate nuclear weapons from the face of this Earth.” He and Takeshi Araki, Hiroshima’s mayor at the time, placed a wreath at the monument bearing the names of the victims of the bombing. An Associated Press account of the visit noted that the Carters “moved silently through the museum. They paused at the final display—the shadow of a man, whose body was disintegrated in the blast and was burned into a set of stone steps.”   

There are fewer details on Nixon’s visit. It came after he had been Dwight Eisenhower’s vice president, and was the last part of a 24-day tour of Asia. A report at the time from United Press International noted that the would-be president “laid the wreath and stood for two minutes of silent prayer as about 60 persons, mostly high-school students and a few American personnel, looked on.” Hiroshima, he said, “has made the world promise to strive for peace.”

Nixon’s own views on the use of the nuclear weapons were complicated. On the 40th anniversary of the Hiroshima bombing, he praised General Douglas MacArthur’s view of the use of atomic weapons in war.

“MacArthur once spoke to me very eloquently about it, pacing the floor of his apartment in the Waldorf,” he said. “He thought it a tragedy that the bomb was ever exploded. MacArthur believed that the same restrictions ought to apply to atomic weapons as to conventional weapons, that the military objective should always be limited damage to noncombatants.  ... MacArthur, you see, was a soldier. He believed in using force only against military targets, and that is why the nuclear thing turned him off.”

But in a 1985 interview, Nixon acknowledged that he considered using nuclear weapons four times during his presidency, including once to end the Vietnam War.

The prospect of a presidential visit remains controversial seven decades after the U.S. bombing Hiroshima and Nagasaki that killed an estimated 140,000 people. This, in part, is because of how the U.S. and Japan view World War II, Sheila Smith, a Japan expert at the Council on Foreign Relations, told NPR. In Japan, she said, a poll last year found nearly 80 percent of people thought the atomic bombs should not have been used on the two cities. “In the United States,” she noted, “when we think of World War II, our war memories revolve around Pearl Harbor.”

When John Kerry, the U.S. secretary of state, visited the Hiroshima Peace Memorial last month, he spoke of the “extraordinary complexity of choices of war and what war does to people, to communities, countries, the world.” He did not, however, apologize. Nor indeed has any American official apologized for the use of nuclear weapons on Hiroshima and Nagasaki—though President Eisenhower had publicly regretted the use of “that awful thing.”

Obama, who will visit Hiroshima later this month with Shinzo Abe, the Japanese prime minister, is likely to remain firmly among their ranks. Ben Rhodes, the deputy national security adviser, wrote in a blog post on Medium Tuesday that the president “will not revisit the decision to use the atomic bomb at the end of World War II.”

“Instead,” Rhodes wrote, “he will offer a forward-looking vision focused on our shared future” with Japan.