Looks like this has devolved into a conversation about the bomb being dropped on Japan so I will say this. The US was not going to spend years of work and millions of dollars on proof of concept on a nuclear bomb and then not use it in a spectacular fashion. Further at the time the Soviet Union did not have a bomb and had the largest army in the world. Truman was surrounded by many advisors (many Nazi sympathizers) who were already viewing the Soviet Union as the US’s major rival in the post war scramble for resource. One cannot discount that in addition to the huge political advantage to Truman of appearing tough on the Japanese, whom everyone hated, dropping the bomb was also intended to send a signal to the Soviets that any efforts to challenge US hegemony would be crushed by overwhelming force.