Manhattan Project Leaders: Harry S. Truman

President Truman approved the atomic bombings of Hiroshima and Nagasaki.

National Archives

Quick Facts

Significance:

33rd President of the United States

Place of Birth:

Lamar, MO

Date of Birth:

May 8, 1884

Place of Death:

Kansas City, MO

Date of Death:

December 26, 1972

Place of Burial:

Independence, MO

Cemetery Name:

Harry S. Truman Presidential Library & Museum

FDR’s Vice President from January to April of 1945, Harry S. Truman assumed the 33^rd Presidency of the United States on April 12 upon FDR’s death. A Democrat from Lamar, Missouri, Truman only learned of the existence of the Manhattan Project the day after FDR’s death, though the project had existed for almost three years prior.

On June 1, 1945, having conferred with top advisors including Secretary of War Henry Stimson, Truman agreed that an atomic bomb should be used against Japan to hasten the war’s end. In late July, 1945, Truman informed Soviet Premier Joseph Stalin of the existence of this powerful weapon. On July 26, the United States, Great Britain, and the Soviet Union issued the Potsdam Declaration, urging Japan’s unconditional surrender lest the country be met with incomprehensible destruction. Japan’s response was unclear, and with Truman’s approval, the United States dropped atomic bombs on Hiroshima and Nagasaki on August 6 and 9, respectively, destroying both cities and killing or wounding hundreds of thousands of people. Japan formally surrendered on September 2, 1945.

After the war, on August 1, 1946, Truman signed the Atomic Energy Act, putting nuclear production under civilian rather than military control and creating the Atomic Energy Commission which ultimately replaced the Manhattan Project.

Learn more about Truman through the Harry S. Truman National Historic Site in Missouri.