There is no easy answer for this question, as opinions depend on the place and time period you refer to. Right after the bomb was dropped, most Americans believed Truman had made the right choice. Japan's behaviour in other countries had been appaling, and they did not seem ready to surrender. Moreover, most people did not know what the effects of the atomic bomb were.
More recently, public opinion has changed. Now we know the extent of destruction that the bomb caused, in particular to civilians. We also know about the long-lasting effects of this catastrophe. As we learned more about the war itself, some people argued that Truman had other alternatives that would have been better choices.
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