Remembering Hiroshima on the 72nd anniversary of the deadliest atom bomb attack

On August 6, 1945, the world witnessed the devastating impact of nuclear weapons for the very first time, when a U.S. plane dropped the atomic bomb “Little Boy” on the Japanese city of Hiroshima.

The shell of a building that was once an exhibition center and government office in Hiroshima sits amid rubble, one month after the first atomic bomb was dropped. The site is now part of the Hiroshima Peace Memorial which was designated a UNESCO World Heritage Site.

The Survivors of the atomic bomb await emergency medical treatment in Hiroshima.

In this 1945 file photo, then-U.S. President Harry Truman sits before a microphone at the White House in Washington, where he broadcast a message on the formal surrender of Japan.Truman never expressed regret for using nuclear weapons in wartime. He argued that it prevented an even more fearsome death toll from an Allied invasion of Japan.

Col. Paul W. Tibbets stands beside Enola Gay(named after his mother) that dropped the atomic bomb. In a 1975 interview, he said that 'I'm not proud that I killed 80,000 people, but I'm proud that I was able to start with nothing, plan it and have it work as perfectly as it did'.

People offer prayers at the Peace Memorial Park in Hiroshima, western Japan, Sunday, Aug. 6, 2017, to mark the 72nd anniversary of the world's first atomic bombing that killed 140,000 people in 1945.

Hiroshima Mayor Kazumi Matsui, right, hands over the name list of newly added victims.

People attend a ceremony to mark the 72nd anniversary of the world's first atomic bombing.

Organizers of a peace prayer light up torches on floats on the Motoyasu River next to the Atomic Bomb Dome in Hiroshima.Hiroshima's appeal of 'never again' on the anniversary Sunday has gained urgency as North Korea moves ever closer to acquiring nuclear weapons.