Answer:
President Truman himself felt he was justified in the use of atomic bombs. He said that it was the right thing to do on the grounds that doing so saved would shorten the war and save many American lives.
Further explanation:
Notice that Truman's rationale spoke about the loss of life by American soldiers if a war on the ground were pursued in Japan. It did not as much take into account Japanese lives, though many Japanese soldiers would also have lost their lives in conventional warfare if that were pursued. And the atomic bombs killed an estimated 150,000 persons in Hiroshima and an estimated 75,000 persons in Nagasaki in a very short time. Added to that were all sorts of severe, negative health effects that contributed to sickness and early death to many more people due to radiation from the bombs. So on that basis, the use of the atomic bombs was not so justifiable. Many have questioned the ethics of using the bombs rather than pursuing other alternatives for ending the war.