What was the atomic bombing of Nagasaki and Hiroshima?

After
Germany surrendered in 1945, endingin Europe, the Allies, including the U.S., France, England
and the Soviet Union, demanded Japan's unconditional surrender. The Japanese refused, meaning
the Allies would have to invade the Japanese mainland, ensuring a bloody and expensive campaign
to take the territory step by step. 

In the meantime, by the end of July,
1945, the U.S. had finished work on two atomic bombs, one uranium based and one plutonium based.
When the Japanese refused to surrender, President Truman authorized the use of these bombs. On
August 6, the first atomic bomb was dropped on Hiroshima, destroying the city and killing about
100,000, half on the first day. On August 9, when the Japanese had still not surrendered, the
U.S. dropped a second bomb, this one plutonium based, on the city of Nagasaki. This led to
between 39,000-80,000 deaths. While...