Furthermore, I have another question related to nuclear weapons. How did Truman react to the effects of the atomic bombings in Hiroshima and Nagasaki? I heard that as FDR's VP, he wasn't kept too in the loop about the Manhattan Project, and after Roosevelt's untimely death, he signed off on the bombings, not knowing fully of the true destructive power. After he heard about the effects in Hiroshima and Nagasaki, he purportedly went into a deep depression. Is any of this true?

The primary objective was to stop the war once and for all, or at least that's the official one. Japanese soldiers could be very fanatical, so fanatical in fact that even after the surrender, some groups refused to surrender for years. It's up to anyone's guess how many years the war could have lasted without the bombs.

But the world is never that simple is it... It's impossible that there weren't other interests in detonating those bombs.

It's very likely that one of the other objectives was to demonstrate USA power to USSR (and the rest of the world), but I think it was more so Stalin would not interfere with USA interests in the future or openly show hostility, in general sense, not just in Asia.

I also believe there were scientific interests. What's better to study the effects of the most powerful weapon in the world than a fake city with dummy civilians? A real one with real people. I admit this is entering the conspiracy theory territory, but I think it's irresponsible to deny this without at least some thought.