Japan's prime minister has offered "sincere and everlasting condolences" for the US service members who died when his country attacked Pearl Harbour, catapulting America into the Second World War.
Shinzo Abe paid a historic visit to the Hawaii site with Barack Obama, becoming the first Japanese leader to visit the USS Arizona Memorial and the first to visit Pearl Harbour with an American president.
The former enemies came together on Tuesday to acknowledge the tremendous loss from the Japanese attack on US military installations in Hawaii in 1941.
"As the prime minister of Japan, I offer my sincere and everlasting condolences to the souls of those who lost their lives here, as well as to the spirits of all the brave men and women whose lives were taken by a war that commenced in this very place," Mr Abe said.
After a formal meeting, Mr Abe and Mr Obama placed a pair of green and peach wreaths made of lilies aboard the USS Arizona Memorial and tossed purple flower petals into the water.
The rusting wreckage of the sunken ship where more than 1,000 American service members are entombed can be seen just under the water's surface.
Mr Obama and Mr Abe closed their eyes and stood silently for a few moments before concluding their visit to the memorial and heading to nearby Joint Base Pearl Harbour-Hickam, where both leaders spoke.
Mr Obama said Mr Abe's visit was a "historic gesture" that showed the power of reconciliation.
He said Mr Abe's presence was a reminder of what was possible between nations and peoples and that wars could end and enemies could become allies.
Mr Obama said it showed "the fruits of peace always outweigh the plunder of war" and the US-Japan relationship was now a cornerstone of peace in the world.
The president singled out Pearl Harbour survivors in the audience, saying the nation saluted them.
The visit is powerful proof that the former enemies have transcended the recriminatory impulses that weighed down relations after the war, Japan's government has said.
Although Japanese leaders have visited Pearl Harbour before, Mr Abe was the first to visit the memorial constructed on the hallowed waters above the sunken USS Arizona.
For Mr Obama, it is probably the last time he will meet a foreign leader as president, White House aides said. It is a bookend of sorts for the president, who nearly eight years ago invited Mr Abe's predecessor to be the first leader he hosted at the White House.
And for Mr Abe, it is an act of symbolic reciprocity, coming six months after Mr Obama became the first sitting US president to visit Hiroshima in Japan, where the US dropped an atomic bomb in hopes of ending the war.
"This visit, and the president's visit to Hiroshima earlier this year, would not have been possible eight years ago," said Daniel Kritenbrink, Mr Obama's top Asia adviser in the White House.
"That we are here today is the result of years of efforts at all levels of our government and societies, which has allowed us to jointly and directly deal with even the most sensitive aspects of our shared history."
More than 2,300 Americans died on December 7 1941, when more than 300 Japanese fighter planes and bombers attacked. More than 1,000 others were wounded.
In the ensuing years, the US incarcerated about 120,000 Japanese-Americans in internment camps before dropping atomic bombs in 1945 that killed some 140,000 people in Hiroshima and 70,000 in Nagasaki.
Mr Abe will not apologise for Pearl Harbour, his government has said. Nor did Obama apologise at Hiroshima in May, a visit that he and Mr Abe used to emphasise their elusive aspirations for a nuclear-free future.
But Alfred Rodrigues, 96, a US Navy veteran who survived what President Franklin D Roosevelt called a "date which will live in infamy", said there was no apology needed.
"War is war," Mr Rodrigues said as he looked at old photos of his military service. "They were doing what they were supposed to do and we were doing what we were supposed to do."
Mr Abe's visit is not without political risk given the Japanese people's long, emotional reckoning with their nation's aggression in the war.
Though the history books have largely deemed Pearl Harbour a surprise attack, Japan's government insisted as recently as this month that it had intended to give the US prior notice that it was declaring war and failed only because of "bureaucratic bungling".
"There's this sense of guilt, if you like, among Japanese, this 'Pearl Harbour syndrome' that we did something very unfair," said Tamaki Tsukada, a minister in the Japanese embassy in Washington.
"I think the prime minister's visit will in a sense absolve that kind of complex that Japanese people have."
Since the war, the US and Japan have built a powerful alliance that both sides say has grown during Mr Obama's tenure, including strengthened military ties. Both Mr Obama and Mr Abe were driving forces behind the Trans-Pacific Partnership, a sweeping free trade deal now on hold due to staunch opposition by Congress and US president-elect Donald Trump.
Moving beyond the painful legacy of the war has been easier for Japan and the US than for Japan and its other former foes, such as South Korea and China. As Mr Abe arrived in Hawaii, Beijing dismissed as "wishful thinking" the notion that Japan could "liquidate the history of World War II" by visiting Pearl Harbour.
"Japan can never turn this page over without reconciliation from China and other victimised countries in Asia," said Hua Chunying, a Chinese foreign ministry spokeswoman.