- The first reason is that the military leadership of Japan did not surrender after the bombing of Hiroshima. They hoped that by dropping a second bomb, the US could shock Japan into surrendering.
- The second reason is that the US wanted to demonstrate the power of its nuclear weapons. They hoped that this would deter other countries from developing their own nuclear weapons.
- The third reason is that the US wanted to avoid a costly and bloody invasion of Japan. They believed that the atomic bombs would save lives by forcing Japan to surrender quickly.