The decision to drop atomic bombs on Hiroshima and Nagasaki was made by the United States government during the final stages of World War II. At the time, the US was engaged in a brutal war against Japan, which had been going on for several years. The Japanese military was fiercely resistant and unwilling to surrender, and the US was seeking a way to bring the war to a swift and decisive end.
Hiroshima was chosen as the primary target for the atomic bomb for several reasons. First, it was a major industrial city and a center for military operations, making it a strategic target. Second, it was believed that the city had not been heavily damaged by previous bombing raids, which meant that the full effects of the atomic bomb could be more easily observed. Finally, the geography of the city - it was situated in a valley and surrounded by hills - was expected to amplify the destructive power of the bomb.
The US military also believed that dropping the atomic bomb on Japan would force them to surrender and bring an end to the war. They hoped that the shock and devastation caused by the bombing would convince Japanese leaders to accept the terms of surrender that had been offered by the Allies. While some historians argue that the use of atomic bombs was unnecessary and excessive, others believe that it was a necessary measure to bring an end to the war and save lives on both sides.