Japan marked the 70th anniversary of the devastating atomic bombing of Hiroshima in the closing days of World War II with calls to step up efforts to eliminate nuclear weapons, even as Tokyo still struggles to come to terms with its role in the conflict.

On Aug. 6, 1945, a U.S. B-29 dropped "Little Boy," the world's first atomic bomb to be used in war, on the southern Japanese city, causing the deaths of between as 90,000 and 166,000 people, according to widely accepted figures. The bombing was followed up by a strike three days later on another southern city, Nagasaki.

Today, tens of thousands of people stood for a minute of silence in Hiroshima at 8:15 a.m. local time, the moment the bomb detonated seven decades ago. Doves were released as a symbol of peace.

Hiroshima Mayor Kazumi Matsui called nuclear weapons "the absolute evil and ultimate inhumanity."

"President Obama and other policymakers, please come to the A-bombed cities, hear the hibakusha (surviving victims) with your own ears, and encounter the reality of the atomic bombings," Matsui said, referring to next year's G-7 summit to be held in Japan, according to The Associated Press. "Surely, you will be impelled to start discussing a legal framework, including a nuclear weapons convention."

The decision in 1945 by President Harry Truman to unleash the destructive power of the bombs on a Japan that had refused unconditional surrender was made after war planners estimated that a military operation to invade the Japanese home islands could cost more than a half-million American lives.

As NPR's Geoff Brumfiel reports today, the choice to bomb Hiroshima rather than an unpopulated area or a military target was made because those less lethal options "wouldn't show the world the power of the new bomb."

The anniversary comes as Japanese Prime Minister Shinzo Abe has tried to push through legislation to expand the country's military capability, which was limited to a purely defensive posture following World War II.

Reuters reports that a government report issued Thursday acknowledges that Japan's "reckless war" did great damage in Asia, but Abe reportedly has taken issue with the term "aggression" to describe his country's actions.

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