- Japanese Civilians
If an invasion were to take place, almost all Japanese citizens--including women, seniors and juveniles--would have been ordered fight the Allied forces.
- The Japanese Cabinet
The atomic bombings were the only Allied actions powerful enough to get the Japanese Cabinet to discuss surrender.
- Civilian Leaders vs. Military Leaders
Civilian leaders were able to use the atomic bomb to push for surrender. The destruction of the two cities served as a new and irrefutable argument against the military leaders who were steadfastly against surrender. One of the emperor's closest advisors stated that "We of the peace party were assisted by the atomic bomb in our endeavor to end the war." (Atomic bombings of Hiroshima and Nagasaki)
- Soviet Union
Immediate end to the war would give Soviets less concessions at the peace table after Japanese surrender. It would also help control their aggression in Europe.
- Not enough warning to civilians
The Interim Committee decided not give Japan a warning prior to the bombings. Even though Truman issued a national leaflet and radio campaign to warn of further attacks after Hiroshima, Nagasaki didn't recieve leaflets until after the bombings.
- Japan on the verge of surrender
Japan was already weakened from constant air raids, air and naval blockades cutting off the flow of all supplies. The Soviet Union's entrance in the war pushed Japan further towards surrender.
- Unconditional surrender
The unconditional surrender demanded by the Allies made it uneccessarily difficult for Japan to surrender. Japan's only concern was retaining their emperor, and this was a condition the Allies could've allowed to avoid the devastation of the atomic bombs.
- Soviet Union
The U.S. wanted intimidate the Soviet Union with the destructive power of the atomic bombs. The bombs were also an exercise of power over the Soviet Union in addition to efforts minimizing it's post-war gains.