This month, President Obama will become the first incumbent American president to visit Hiroshima, the Japanese city that was devastated when the United States dropped an atomic bomb on Aug. 6, 1945.

That bomb — and a second atomic blast on Nagasaki on Aug. 9 — effectively ended World War II; Japan surrendered six days after the Hiroshima bombing. However, the human costs were huge. Estimates of those killed go as high as 150,000, and even for those who survived, it was a hellish, life-altering experience. At the same time, many believe that the bomb was preferable to a planned invasion of Japan, which would have likely brought massive casualties among civilians, Japanese forces and Allies.

During his visit to the city, Obama is expected to give a speech on nonproliferation of nuclear weapons — a topic that he has touched on many times before. He is not expected to apologize for the bombing itself.

Even so, such a visit may reflect shifting viewpoints of Americans on Hiroshima. Last year, Pew Research Center compiled a number of polls about public attitudes to the bombings in America and Japan.

Bells tolled and thousands bowed their heads in prayer in Hiroshima on Thursday at ceremonies marking the 70th anniversary of the world’s first atomic bombing. (Reuters)

In the first Gallup poll from 1945 just after the bombings, a huge 85 percent of Americans approved the bombings. However, figures from 2005 show a significant decline to 57 percent. Meanwhile, another poll conducted by the Detroit Free Press in the United States and Japan in 1991 found that 63 percent of Americans thought that the bombings were justified in a bid to end the war, while just 29 percent of Japanese did.

When Pew followed up on that question in 2015, they found that the numbers of people who thought the bombings were justified had dropped in both America and Japan — to 56 percent among Americans and just 14 percent among Japanese. The total percentage of people who thought the bombings were unjustified stood at 79 percent in Japan, up from 64 percent in 1991. In America, those who thought they were unjustified rose to 34 percent, from 29 percent in 1991.

The difference in viewpoints between the United States and Japan is obvious — one country dropped bombs on the other, after all — but there are also some more subtle things going on. Last year, WorldViews took a look at how the bombings were taught in countries all over the world. They have long been a major topic of study for Japanese and American children. But, in recent years, the way the bombings are taught to Americans has shifted, with more emphasis put on the bombs' human toll and not just the strategic value.

"The textbook has walked away from this idea that it speaks with this omniscient voice and it tells you facts," Christopher Hamner, a history professor at George Mason University, told WorldViews. "Textbooks will have documents from both sides. They acknowledge that there are multiple perspectives."

This change may have contributed to a generational shift seen in Pew's research: Just 47 percent of Americans 18 to 29 years old said the use of atomic weapons was justified when asked last year, compared to 70 percent of those 65 or older.

G7 ministers visit the Hiroshima Peace Memorial, including John Kerry, who has become the first U.S. Secretary of State to do so. (Reuters)

The widespread support for the bombing of Hiroshima among Americans has long led incumbent U.S. presidents to refuse to visit the city, fearing it would be construed as an apology. Obama's visit seems to reflect the perception that support for the bombings has dropped, even if he doesn't apologize.

While many Japanese view the bombings as unjustifiable, some in Hiroshima may well be satisfied even without an apology.

"What's done is done," one Hiroshima resident told The Washington Post in 2009. "I don't need an apology. But if Obama hasn't seen what an A-bomb can do to you, then he should come and look."

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