Historical Context

The main reason why the world war started, was because of the  National Socialst German workers, or the Nazi party. Adolf Hitler  leader of the Nazi party was there for Germany when they were at its weakest, they needed a leader, and that's exactly what he did, he became the Chancellor in 1933. 
War broke out in Europe, when Germany attacked Poland, and the Axis of power, Germany, Japan, and France were very powerful. 
On December 7, 1941 Japan shocked the world by launching a surprise attack on American forces. Known as the bombing of Pearl Harbor, over 2000 men were killed, thanks to 353 Japanese fighter planes. The following day, December 8th American President Franklin Rooselvelt announced war in japan.

               " December 7, 1941 – a date which will live in infamy — the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan. " President Roosevelt."
Lisa Meitner was a scientist who discovered a way to split uranium atoms.  This allowed a bunch of scientists to see military potential of this discovery. Which in hand built the bomb. ( Frank, Sandy)

“ The first atomic bomb was explodes at los Alamos on july 6, 1945.  and this was a test bomb, just to see the effects of the bomb. ( Frank, Sandy)