- Finding himself President after the sudden death of Franklin D. Roosevelt, Harry S. Truman was President until 1953. As such, it was Truman who gave the order to drop the atomic bombs on Hiroshima and Nagasaki. Truman did not have the “need to know” about the Manhattan Project until FDR died (hell, Josef Stalin and his spies knew about the Manhattan Project before Truman did). Thus he took the decision to use them in a bit of an information vacuum, something historians have subsequently either downplayed or over-emphasized. He also desegregated the US military in 1948, because of his disgust over the way African-American war veterans were treated; the fact that it also saved some tax dollars getting rid of that ridiculous redundancy helped sell it too.