The United States dropped an atomic bomb on the Japanese city of Hiroshima 65 years ago, killing an estimated 140,000 people.
It brought a swift end to World War II and since then, the US and its allies have avoided annual ceremonies commemorating that day.
However, this year Britain, France, the US and even Ban-Ki moon, the UN secretary-general, will be attending the ceremony in Hiroshima for the first time.
For atomic bomb survivors attending, the ceremony offers hope of a world that one day could be free of nuclear weapons.
Al Jazeera's Steve Chao reports.
Source: Al Jazeera