Haunting photos show the day the US dropped an atomic bomb on Hiroshima

On May 7, 1945, after World War II had been fought for almost six years, Germany surrendered to the Allies—including Britain, China, the Soviet Union and the US—but instead of following suit, Japan continued to fight. They made it clear they would fight until the bitter end.

Sources: Aljazeera

The Allies' casualties grew worse during this period. Between April and July, the Japanese killed as many as half of the total casualties they had inflicted over the previous three years of the war.

Sources: History.com

In April, President Harry Truman was sworn in. Until then, he had not known about the work being done by J. Robert Oppenheimer and his team on the Manhattan Project to build an atomic weapon. But with Japan's refusal to surrender, he soon came around to the idea of using it.

Some generals argued the war should have been ended with a final invasion into Japan, but they also advised that it could result in the deaths of up to 1 million US troops. 

Truman didn't wanted more US soldiers to die so he chose to proceed with the atomic bomb if Japan wouldn't surrender. 

Many military leaders believed the atomic bomb was unnecessary and that Japan would surrender without the use of atomic bombs.

But a committee of advisors, led by the Secretary of War Henry Stimson, argued there was a consensus that backed the bomb and that it needed to be dropped to end the war.

Sources: History.com, Al Jazeera

On July 16, a test atomic bomb was successfully detonated in New Mexico. Less than a fortnight later, on July 26, Truman made the Potsdam Declaration. He told Japan to unconditionally surrender or face "prompt and utter destruction."

Japan ignored Truman's demand for surrender. 

US intelligence also showed that Japan, which had 2.5 million troops, was preparing for an American invasion. 

Japan had readied thousands of suicide planes and more than 560,000 soldiers for an expected US invasion. Reports also showed that Japan planned on executing all US prisoners as soon as US armed forces landed in Japan. 

Sources: AHF, NationalWW2Museum, BBC, History.com, Al Jazeera, New York Times

The plan to use the atomic bomb proceeded. A crew of 12 was assembled on a US military base on Tinian, an island in Northern Marianas in the Pacific. Colonel Paul Tibbets was named pilot and Captain Robert Lewis was his co-pilot.

Captain William Parsons was weaponeer and Second Lieutenant Morris Jeppson was the electronic test officer.

Sources: AHF, New York Times  

On August 5, the crew was briefed about their mission. Hiroshima, a city of approximately 350,000 people, which had an active military base, had been chosen for bombing.

Tibbets told the crew they would be dropping bombs on the city, but he didn't tell them they would be dropping an atomic bomb.

Sources: History.com, NationalWW2Museum

The atomic bomb was called "Little Boy." It was a 10 foot long uranium bomb that weighed 9,788 pounds

Sources: The History Press, History.com, PBS

On August 5, Little Boy was loaded onto an American B-29 bomber Tibbets had called "Enola Gay" after his mother. It was confirmed that the drop would take place the next day.

Sources: The History Press, History.com, PBS

At 12:15 a.m. on August 6, the crew listened to a prayer composed for the occasion. At the time, there was no certainty that the flight would survive the explosion.

Sources: AHF, NationalWW2Museum

At 2:45 a.m., Enola Gay and two other B-29 observation bombers took off. Because Enola Gay's cargo was so heavy, it required the entire 2 mile runway to take off.

Three weather planes also left Tinian. 

Each one flew to a potential target city—Hiroshima, Kokura and Nagasaki—to check if weather conditions would permit a bomb drop.

Sources: The History Press, AHF

At 3 a.m., Parsons and Jeppson began to arm Little Boy. They inserted gunpowder and a detonator into the bomb. At 7:15 a.m., they removed the safety devices and inserted arming devices. Little Boy was ready to be deployed.

Sources: AHF

At 7:30 a.m., Tibbets told his crew, "We are carrying the world's first atomic bomb."

At 8:24 a.m., the weather plane over Hiroshima relayed that it was fine to proceed. Tibbets told his crew it had been confirmed. He said, "It's Hiroshima."

The plan was to drop the bomb on the Aioi Bridge, a T-shaped bridge that Tibbet had earlier said was, "the most perfect aiming AP (aim point) I've seen in this whole damn war."

Sources: NationalWW2Museum, AHF

At 8:15 a.m. local time, Little Boy, the world's first atomic bomb used in battle, was dropped from 31,060 feet in the sky. It fell nearly six miles in 43 seconds before exploding 1,900 feet from the ground.

Witnesses recalled a flash of blinding light before a giant mushroom shaped cloud filled the sky. 

The fireball grew 900 feet in diameter. The power of the blast was the equivalent of 12-15,000 tons of TNT. 

Tibbets pulled a sharp 155 degree turn as soon as the bomb was dropped, knowing there was less than 45 seconds to get away. 

By the time the bomb exploded, Enola Gay was 11.5 miles away.

Sources: BBC, The History Press, AHF, NationalWW2Museum

The mushroom cloud reached about 2,500 feet into the sky. At the core of the fireball the temperature was 300,000 degrees Celsius, while the surface was 7,000 degrees Celsius.

Tibbets later wrote about the explosion in his memoir, describing the mushroom cloud, as "boiling upward like something terribly alive."

Sources: The History Press, History.com, AHF, BBC, New York Times

At the time, it was then the most destructive bomb used in the history of war. The explosion instantly wiped out five square miles of Hiroshima, including 62,000 buildings. Up to 80,000 people were killed instantly.

Another estimated 55,000 or so people would die by the end of 1945 from the effects of the explosion, including radiation poison and burn wounds.

According to the US Department of Energy's Manhattan Project history, the final death count over the next five years was almost 200,000.

Sources: BBC, Al Jazeera, The History Press, History.com, AHF

The explosion was so devastating people were vaporized leaving nothing behind except for their "nuclear shadow." These shadows were actually what the surfaces looked like before the blast, but appeared dark in comparison to everything else that was bleached by the atomic heat.

Sources: AHF, LiveScience

Roof tiles were fused by the heat, while bronze and granite statutes melted away. Across the city, fires began to spread causing even more damage.

Sources: BBC, The History Press, NationalWW2Museum, AHF

After the explosion, the Enola Gay circled the city three times before turning back towards the base. It wasn't until they were 368 miles from the city that they could no longer see the mushroom cloud.

Sources: AHF

At 2.58 p.m., the Enola Gay landed back on Tinian. The mission had only taken about 12 hours, and while it was not enough to end the war, it had changed the world.

Sources: AHF

About 16 hours after the bomb was dropped, Truman told Japanese leaders if they did not "now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this Earth."

He said the US was now "prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city."

"We shall destroy their docks, their factories, and their communications. Let there be no mistake; we shall completely destroy Japan's power to make war," he said.

Sources: AHF

Three days after the bomb was dropped on Hiroshima, a second, more powerful bomb known as the "Fat Man" was dropped on Nagasaki, killing an estimated 70,000 people including those who later succumbed to the effects of the bomb by the end of 1945.

Sources: PBS, BBC

On August 14, 1945, Japan surrendered and World War II was officially over. The Japanese Emperor Hirohito announced the surrender via a recorded radio message.

Sources: AHF