The American government funds scientists to develop a deadly nuclear weapon to force Japan to surrender. By the time the Manhattan Project ends, Germany has surrendered, Italy surrendered, and Japan was about to lose, but still refused to surrender. President Trumen decided to drop a bomb rather than send American soldiers to add more American casualties.
On August 6, 1945, Enola Gay dropped Little Boy, and killed tens of thousands of people in Hiroshima, Japan.
On August 9th, 1954, another atomic bomb, nicknamed Fat Man, was dropped on Nagasaki, Japan. Between 120,000 and 220,000 people were killed immediately.
On August 15th, 1954, Japan surrendered to the United States, officially ending WW2.