NARRATOR: The Enola Gay's mission starts from Tinian in the Marianas.
The crew has had their final briefing on weather
and air sea rescue.
Only yesterday they have been told of the true power
of the weapon they are to carry.
(SIREN BLARES)
LIV: At 2:45am on 6 August 1945, a US aircraft called the Enola Gay
took off towards Japan.
The massive bomb has been loaded.
Six and a half hours later, it dropped a nuclear weapon,
or atomic bomb, on the city of Hiroshima...
At 9:15, the bomb is dropped.
..instantly killing up to 80,000 people.
At the start of the Second World War in 1939,
there was no such thing as an atomic bomb,
but there were scientists who realised that it was possible
to create a huge amount of energy by splitting atoms
in a process called nuclear fission...
..and some were worried about what would happen
if Nazi Germany developed such a weapon first.
At that point, the US wasn't actually involved in World War II...
..but that changed in December 1941
when Japan attacked the US's navy base
at Pearl Harbor in Hawaii.
The US and Japan were now at war,
and the American government secretly began development
of the world's first nuclear bomb.
NARRATOR: Our greatest secret from...
Its codename? The Manhattan Project.
More than 100,000 people were involved in the research,
although many didn't know what exactly they were working on.
On July 16, 1945,
the US successfully detonated the first atomic bomb
at a test site in New Mexico.
(CHEERING)
Meanwhile, the war had turned for the Allies,
and on 8 May 1945, Germany surrendered.
WINSTON CHURCHILL: The German war is therefore at an end.
But Japan didn't, and in the Pacific,
fighting still raged between Japan and the Allies,
including the US, Australia and the UK...
..so the United States government decided to use its new weapon.
Three days later, the US dropped a second atomic bomb
on another Japanese city called Nagasaki.
Less than a week later,
Japan surrendered and World War II finally ended.
But for the people of Hiroshima and Nagasaki,
the nightmare of the bombings and the destruction they left behind
was far from over.
As well as the instant destruction,
the nuclear weapons left radioactive waste
and spread nuclear fallout,
which is a radioactive dust that can make people really sick.
In the months and years after Hiroshima and Nagasaki,
hundreds of thousands died
from being exposed to the radiation left behind by the bombs.
NEWSREEL NARRATOR: First you duck, and then you cover.
Nuclear weapons and people's fear of them
would go on to have a huge impact on the world for decades.
Eventually, many countries around the world agreed
to stop making and testing them, but some say we need to do more
to make sure they're never used again.
(CHILDREN SING)
Here in Hiroshima, the bomb will never be forgotten,
and 75 years on,
many are hoping it remains a lesson for the rest of the world
on the terrible consequences of nuclear warfare.