I think that Truman dropping the Atomic bomb on the two Japanese cities is justifiable. The US government gave the Japanese a warning before the first one, and a warning before the second one. It is the Japanese fault that it was dropped. If they would have surrendered after the warning, and even after the second warning, then more people would be alive.
I also think it is a good thing that Truman dropped the atomic bomb on Japan because now that we did that, Japan and the USA have a better relationship as countries. It is good that we did it also because now the world knows the power that it has on cities and the world. It is better than a nuclear war breaking out with more atomic bombs on more cities and more deaths.
On the other hand, it is so wrong to kill so many people just to destroy a military base. We wouldn't like it if Japan blew up area 51 with a nuclear bomb, and all the radiation killed everyone in Las Vegas. In my opinion, it is wrong to kill innocent people in a war between governments.
All in all, I am still not sure what my opinion is. For all we know, if we didn't drop the two bombs on Hiroshima and Nagasaki, we might not have ended the war.