Harry S. Truman was president of the United States from April 12h, 1945, until Jan. 20, 1953. Truman served as vice president during Franklin D. Roosevelt's fourth term as president, which lasted only 82 days. When Roosevelt died, Truman became president.
During his brief tenure as vice president, Truman was not briefed on the development of the atomic bomb. Within months of his installment as president, he was faced with the decision of whether or not to use this new weapon. He chose to approve its use, and two atomic bombs were dropped on Japan. These bombings and concurrent Soviet victories effectively ended World War II.