The atomic bomb is particularly famous for having been the key to ending World War II. The United States decided to use the bomb in Japan hoping that this will lead to its surrender. The bomb was developed as a top-secret weapon, and when suggested to Truman, he was not offered any alternatives.
Many critics have argued that the bomb was unnecessarily destructive, and that less lethal alternatives were available. However, it is unclear to what extent Truman could have approached the situation another way. It is very likely that the secrecy under which the bomb had been developed limited Truman's ability to consider alternative approaches. The fact that the weapon was secret meant that few people contributed to the deliberation, and that many of the risks were unknown. Moreover, the situation was complicated due to other concerns, such as a determination to protect American lives and Truman's desire to appear decisive and strong.