U.S. President Barack Obama paid moving tribute to atomic bombing victims, reaffirmed the U.S.-Japan security alliance and friendship between both nations and called for the elimination of nuclear weapons in a historic and emotional visit to Hiroshima on Friday.

Obama did not, however, include an apology for the dropping of the atomic bomb, which some in Japan and abroad had sought.

In a solemn ceremony, Obama — the first sitting U.S. president to visit the once-destroyed city — along with Prime Minister Shinzo Abe, arrived at Hiroshima Peace Memorial Park late Friday afternoon to bright sunshine that gradually gave way to a cool evening. Thick crowds jammed the periphery of the park, but it was otherwise quiet as Obama and Abe toured the Peace Memorial Museum and laid wreaths at the cenotaph.

“Seventy-one years ago, on a bright, cloudless morning, death fell from the sky and the world was changed. A flash of light and a wall of fire destroyed a city, and demonstrated that mankind possessed the means to destroy itself. Why do we come to this place, to Hiroshima? We come to ponder a terrible force unleashed in a not-so-distant past,” Obama said in prepared remarks.

Obama spoke of not only Japanese who perished but also those of other nationalities, including 12 Americans.

“We come to mourn the dead, including over 100,000 Japanese men, women and children, thousands of Koreans, a dozen Americans held prisoner. Their souls speak to us. They ask us to look inward, to take stock of who we are, and what we might become,” he said.

Obama also noted it was not the mere fact of history that distinguished Hiroshima from the many memorials to those who perished in the World War II.

“There are many sites around the world that chronicle this war. Memorials that tell stories of courage and heroism. Graves and empty camps that echo of unspeakable depravity. Yet in the image of a mushroom cloud that rose into these skies, we are most starkly reminded of humanity’s core contradiction, of the very spark that marks us as a species, our thoughts, our imagination, our language, our toolmaking, our ability to set ourselves apart from nature and bend it to our will. Those very things also give us the capacity for unmatched destruction,” the president said.

There had been calls among some Japanese and international peace activists and others for the president to apologize for the dropping of the bomb, but Obama said last week that no such apology would be forthcoming. Instead, the president used the occasion to speak about Hiroshima in the broader context of man’s inhumanity to man.

“Nations arise telling a story that binds people together in sacrifice and cooperation, allowing for remarkable feats, but those same stories have so often been used to oppress and dehumanize those who are different. Science allows us to communicate across the seas, fly above the clouds, to cure disease and understand the cosmos. But those same discoveries can be turned into ever more efficient killing machines.

“The wars of the modern age teach us this truth. Hiroshima teaches this truth,” the president said.

“That is why we come to this place. We stand here in the middle of this city and force ourselves to imagine the moment the bomb fell. We force ourselves to feel the dread of children confused by what they see. We listen to a silent cry. We remember all the innocents killed across the arc of that terrible war, and the wars that came before, and the wars that would follow.

“Mere words cannot give voice to such suffering. But we have a shared responsibility to look directly into the eye of history and ask what we must do differently to curb such suffering again.”

Following his speech, which preceded remarks given by Abe, the two leaders met with three hibakusha who had been invited by the Japanese government, shaking hands and offering words. At one point, the president hugged one of the hibakusha.

The U.S. president also invited Shigeaki Mori, another hibakusha, who conducted research on the 12 Americans who perished in the atomic bombing. Mori’s efforts became a film known as “Paper Lanterns,” and was recently released.

Foreign Minister Fumio Kishida told reporters afterward that Sunao Tsuboi, 91, a hibakusha, told the president that he welcomed and thanked him for his visit. Tsuboi also said he felt he became younger just listening to the president’s words about the right to the pursuit of happiness, and that he, too, wanted to work with Obama for a world without nuclear weapons, even after the president leaves office early next year.

Abe also thanked Obama.

“The fact the U.S. president witnessed the reality of the atomic bomb and renewed his pledge for a world without nuclear weapons has given much hope to people around the world who believe in a nuclear-free world.

“Not only the people of Hiroshima, but the entire nation of Japan was looking forward to this historic moment. I’d like to offer my heartfelt respect for the decision and courage shown by Mr. Obama in coming here.”

After the speeches, Obama and Abe strolled past the cenotaph toward the Children’s Peace Monument that commemorates Sadako Sasaki, who was a child at the time of the bombing. Sasaki folded 1,000 paper cranes as a gesture for peace before her death at age 12 in 1955 of acute malignant lymph gland leukemia.

Before arriving in Hiroshima, Obama had made four paper cranes. Two were given to local elementary and middle schoolchildren, and two were put beside the visitors’ book at the museum.

“We have known the agony of war. Let us now find the courage, together, to spread peace and pursue a world without nuclear weapons,” Obama wrote in the visitors’ book.

While the original plan was for Obama to also walk to the Atomic Bomb Dome, security concerns meant the two leaders only viewed the dome from the Eternal Flame of Peace, several hundred meters away.

Initial reactions among Japanese experts to Obama’s speech varied.

“Obama’s mention of over 100,000 Japanese men, women and children, thousands of Koreans, and a dozen American prisoners of war: Even Japanese often neglect to mention this. But he did not mention thousands of American citizens of Japanese descent affected,” said Satoko Oka Norimatsu, director of the Vancouver, Canada-based Peace Philosophy Centre.

“Overall, not perfect. But Obama could have gotten away with just referring to victims in general. So referring to specific groups like ‘children’ and ‘Koreans’ was notable,” she said.

However, she added that one group was missing at today’s ceremony.

“It was almost a misogynistic show. Almost no women at all, except glimpses of Caroline Kennedy here and there. The second hibakusha to talk to Obama should have been a woman, instead of a man who spends his lifetime researching the American POWs who were affected by the bomb,” Norimatsu said.

Tetsuo Kotani, senior research fellow at The Japan Institute of International Affairs, praised the speech, saying Obama’s message was humble and designed not just for the U.S. and Japan but for the world at large.

“In terms of the Japan-U.S. alliance, Obama’s message showed the world that reconciliation is possible without an apology. But the message transcended the alliance and sent a message to the global community. Of course there are people who criticize Obama’s move. But the president’s message was so grand that it transcended such criticism,” Kotani said.

For the U.S., Japan and especially the people of Hiroshima, the president’s decision to visit the city brought mixed emotions, dredged up long-buried memories and reignited a passionate debate about whether the bombing was a necessary gesture that helped end World War II and thus save lives, or an unnecessary war crime.

The Aug. 6, 1945, atomic bombing killed an estimated 140,000 and injured many more who would become known as hibakusha — survivors who to this day still suffer from the fallout of the attack. A second bomb dropped on Nagasaki on Aug. 9 killed an estimated 74,000.

Various groups of hibakusha and their families and supporters had called on Obama to issue an apology. But most, up to 80 percent according to one poll, were not seeking one. They simply wanted Obama, in honoring his pledge in a 2009 speech in Prague to seek a world free of nuclear weapons, to go to Hiroshima Peace Memorial Park, the adjacent Peace Memorial Museum, with its detailed and often graphic photographs of the attack’s aftermath, and, above all, listen to the experiences of those who lived through the blast.

The road to Obama’s Hiroshima visit began in the autumn of 2009 when he indicated publicly he would like to visit at some point. Documents leaked several years later by WikiLeaks showed Japanese officials were against a visit that year, saying the time was not right. There had just been a change of government, with then Prime Minister Yukio Hatoyama of the Democratic Party of Japan having taken office.

In the following years, Hiroshima and Nagasaki launched local campaigns, led by their respective mayors, to invite the president to visit one or both cities. In the autumn of last year, some Japanese media reported that the president was considering a visit.

Behind the scenes, U.S. Ambassador Caroline Kennedy reportedly urged Obama to travel to Hiroshima. And by this spring, with attention turning to the fact that the Group of Seven Ise-Shima summit in Mie Prefecture, which concluded Friday, would likely be his last visit to Japan as president. A successful trip to the city by U.S. Secretary of State John Kerry for the G-7 Foreign Ministers’ meeting in March, in which he said that everybody, including the president, should travel to Hiroshima, helped lay the groundwork for the visit, which was then hastily arranged for after the G-7 summit.

While the murder of 20-year-old Rina Shimabukuro, allegedly by Kenneth Franklin Shinzato, a civilian employee at Kadena Air Base, a week before the G-7 summit and opposition by many U.S. veterans over Obama’s plans created political problems for both Abe and Obama, ultimately it did not affect the visit.