The U.S. Dropped The Atomic Bomb On Hiroshima 70 Years Ago

On Aug. 6, 1945, the United States detonated the world's first atomic bomb over Hiroshima. Seventy years later, we remember that fateful day.

On July 26, 1945, the United States called for the unconditional surrender of Japan under threat of "prompt and utter destruction."

Two days later, newspapers reported that the Japanese government had officially rejected the proposed ultimatum. Soon after, the world's first atomic bomb was dropped over the Japanese city of Hiroshima, killing an estimated 70,000 people instantly upon detonation.

Three days later, a second atomic bomb was dropped, on Nagasaki. With the effects of radiation, the total number of victims is thought to be approximately 340,000 people. On Aug. 15, 1945, the surrender of Japan was publicly announced and World War II was brought to an end.

Aug. 2, 1939: Albert Einstein writes to President Franklin D. Roosevelt, warning of the possibility of an atomic bomb.

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Physicist Albert Einstein writes a letter to President Franklin D. Roosevelt raising the possibility that Germany could build an atomic bomb. The letter led to America building an atomic bomb in what was known as the top-secret "Manhattan Project."

July 16, 1945: America's first atomic bomb is tested at the White Sands Proving Ground.

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An atomic bombshell is hoisted to the top of a tower at Alamogordo, New Mexico. At the White Sands Proving Ground, code name "Trinity" would become the world's first-ever detonation of a nuclear weapon.

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In this sequence of photos, a mushroom cloud is recorded by an Army automatic motion picture camera six miles away as the first atomic bomb test was conducted at Alamogordo, New Mexico.

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Close-up of the ground shows how the heat from the atomic bomb explosion melted sand into glass.

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Nuclear physicist J. Robert Oppenheimer, director of the Los Alamos Laboratory during the development of the atomic bomb, and Major General Leslie Groves inspect the remains of the tower from which an atom test bomb was ignited.

"We knew the world would not be the same," Oppenheimer would later recall. "A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita. Vishnu is trying to persuade the Prince that he should do his duty and to impress him takes on his multi-armed form and says, 'Now, I am become Death, the destroyer of worlds.' I suppose we all thought that one way or another."

July 1945: The decision is ultimately made to use the atomic bomb against Japan.

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After Roosevelt's death brought him to power during the last months of World War II, Harry S. Truman was forced to make the decision to end the war with Japan by dropping the atomic bomb.

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An atomic bomb of the "Little Boy" type, which was detonated over Hiroshima, Japan.

August 5: The crew is briefed prior to the flight of the Enola Gay.

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At a mission briefing, Captain William Parsons and Colonel Paul Tibbets go over last-minute data prior to the atomic bombing of Hiroshima.

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American bomber pilot Paul W. Tibbets Jr. stands with the ground crew of the bomber named the Enola Gay which Tibbets flew — and named after his mother — in the atomic bombing of Hiroshima.

The war department issued shoulder patches to approximately 3,500 Army officers and men assigned to work on the atomic bomb (left). Tibbets, pilot of the Enola Gay, waves from his cockpit before takeoff (right).

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View of the atomic bomb, codenamed "Little Boy," as it is hoisted into the bomb bay.

Aug. 6, 1945: The atomic bomb is detonated over Hiroshima.

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An aerial photograph of Hiroshima, Japan, shortly after the "Little Boy" atomic bomb was dropped.

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Damage in Hiroshima after the atomic bombing of Aug. 6, 1945. A few buildings are still standing, and some telephone and electricity poles remain intact.

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Photo from the U.S. Army Signal Corps showing the devastation left after the first atomic bomb was droppped on Hiroshima.

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A man wheels his bicycle thorough Hiroshima, days after the city was leveled by an atomic bomb blast. The view here is looking west-northwest, about 550 feet from where the bomb landed.

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Heaps of bodies at Hiroshima.

For those who survived, the damage from the bomb's intense heat and radiation caused lasting damage.

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An atomic bomb survivor lies at Hiroshima Red Cross hospital in Hiroshima, Japan.

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A mother tends her injured child, a victim of the atomic bomb blast at Hiroshima.

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A man whose back has been totally burned during the atomic bomb dropped by the U.S. on Hiroshima (left). Two brothers who survived the atomic bombing of Hiroshima (right).

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A victim of the atomic bombing of Hiroshima, Japan, shows the burns on his arms.

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Children in Hiroshima wearing masks to combat the odor of death.

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Officials of Hiroshima, meeting in the once opulent conference room of City Hall, discussing how to repair the ruined city.

In the United States, the bombing was hailed as a triumph.

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Headline from the Chicago Daily News proclaiming the bombing of Japan with the atomic bombs.

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Crewmembers of the Enola Gay, the American B-29 bomber which dropped the atomic bomb on Hiroshima, proudly parade through New York on a jeep.

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Victory over Japan Day (V-J Day) celebration in Jackson Square in downtown Oak Ridge, Tennessee. When the first atomic bomb was dropped on Japan on Aug. 6, 1945, the news reports revealed to the people at Oak Ridge what they had been working on all along.

2015: 70 years later, Hiroshima is rebuilt.

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A vibrant city is bustling after years of rebuilding.

And remembers.

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People visit the Peace Memorial Park to pray for victims of the atomic bombing in Hiroshima.

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Students from Sweden look at exhibits at Hiroshima Peace Memorial Museum at Hiroshima Peace Memorial Park in Hiroshima. The displays are intend to help understanding the damage caused by nuclear weapons.

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An elderly woman places flowers at the monument for atomic bomb victims at the Hiroshima Peace Memorial Park on the day before the 70th anniversary of the atomic bombing of Hiroshima.