When I was in college, I wrote my thesis on weaponry used in today's military back in 1984. The internet had not yet become anything near what it is today, but there was some helpful information that I could use, along with the scores of other knowledge that I obtained from other sources, including the Encyclopedia Britannica. I also wrote to different physicists, which only a few returned answers to my questions, personal interviews with Generals and Admirals and being that I was a student at the Naval Academy, I did have some luck in getting a 15 minute interview with the Joint Chief of Staff, General John Vessey, Jr. We met inside the Pentagon.
When I included the atomic bomb and different nuclear weapons in my thesis, I faced a stumbling block because back then, so much of the information was listed as classified and was not available to the public. It was really a very difficult job getting good information from those people in the know. I really enjoyed writing about these types of weapons, especially the A-Bomb. It really peaked my interest, being that it happened way back in 1945 when nuclear weapons were only thought of seriously in comic books, but then became reality. I mostly interested in the A-bomb. mainly because it had been used in a war and there was more information available about the bomb.
The main question that I never received a straight forward answer to was, "Why did President Truman decide to drop the A-Bomb?" In my opinion, I had received three more probable and credible answers. One was that Truman was in a hurry to end the war. Second answer was that Truman thought by dropping the bombs and ending the war would save American lives on the seas and the battlefield and the third answer was by dropping the bombs, Truman felt it would make the U.S. look like the military giant of the world and that no other country would attempt to go to war with the U.S. He hated the idea of continuing to bomb Japanese owned islands and even trying to invade Japan by storming the beaches.
I did receive other lesser credible answers. I thought some of the answers were more like an opinion. Here are a few. By dropping the bombs, it would save both U.S. military lives
as well as Japanese lives. How could that be? The bomb dropped in Hiroshima killed at least 80,000 just after impact. Over 100,000 Japanese lives were lost between the two bombs that were dropped. Truman wasn't concerned about saving Japanese lives. Another answer received was that by dropping the bombs, the U.S. would be the country where every industry would want to set up shop and be a lifetime partner due to our military strength. That initially did happen for several years before Japan and then China became more industrialized than the U.S.
Here is a very good link provided by the Britannica that explains how the A-Bomb became a game changer un WWII.
Atomic Bomb