The sun rose as normal over Hiroshima on the morning of August 6, 1945. But at about 8:15 in the morning, another blinding sun flashed over the city.

It was the Little Boy uranium bomb, 9-foot 10-inches long and weighing 9,700 pounds, dropped from a height of 31,060 feet.

Forty-three seconds later, the very first atomic bomb to be used in warfare detonated 1,970 ft off the ground, directly above Shima hospital, with a force equivalent to 15,000 tons of high explosives.

It created a flash of light and a fireball 1,200 foot across with a core temperature of more than 1,000,000 degrees Celsius.

In the immediate zone of the blast, victims were literally vaporized, leaving only their shadows on scorched walls and pavements. Virtually every building within a mile of the blast was obliterated by a shockwave faster than the speed of sound.

It’s estimated around 70,000 people were killed instantly or shortly afterward. Over the next two to four months, the acute effects of the bombing killed between 90,000 and 146,000 people in Hiroshima – most of them civilians. Death and illness from the radiation continued to mount for decades.

Orders for the bombing were issued to General Carl Spaatz on July 25 under the signature of General Thomas T. Handy, the acting Chief of Staff.

In his personal diary on the day the order was issued, President Harry S. Truman wrote: This weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop that terrible bomb on the old capital [Kyoto] or the new [Tokyo]. He and I are in accord. The target will be a purely military one.

Shadows of vaporized victims were left on pavement and walls.

On August 9th, the U.S. dropped a second bomb on Nagasaki. Five days later, on August 15th, Japan surrendered to the Allies. On September 2nd, the Japanese government signed the “instrument of surrender” which effectively ended World War II.

Hiroshima in the aftermath of the bombing.

The reconstruction of Hiroshima was begun around 1950 and Hiroshima is now the largest industrial city in that section of Japan.

Atomic Bomb Dome was designated a UNESCO World Heritage Site in in 1996, and remains one of the few buildings not obliterated by the blast