Presidency of Harry S. Truman

Harry S. Truman's tenure as the 33rd president of the United States began on April 12, 1945, upon the death of President Franklin D. Roosevelt, and ended on January 20, 1953. He had been vice president for only 82 days when he succeeded to the presidency. Truman, a Democrat from Missouri, ran for and won a full four-year term in the 1948 presidential election, in which he narrowly defeated Republican nominee Thomas E. Dewey and Dixiecrat nominee Strom Thurmond. Although his existing term was exempt from the newly ratified Twenty-second Amendment that established a two-term limit for presidents, Truman withdrew his bid for a second full term in the 1952 presidential election because of his low popularity. He was succeeded by Republican Dwight D. Eisenhower.

Truman's presidency was a turning point in foreign affairs, as the United States engaged in an internationalist foreign policy and renounced isolationism. During his first year in office, Truman approved the atomic bombings of Hiroshima and Nagasaki and subsequently accepted the surrender of Japan, which marked the end of World War II. In the aftermath of World War II, he helped establish the United Nations and other post-war institutions. Relations with the Soviet Union declined after 1945, and by 1947 the two countries had entered a long period of tension and war preparation known as the Cold War, during which a hot fighting war with Moscow was avoided. Truman broke with Roosevelt's prior vice president Henry A. Wallace, who called for friendship with Moscow and ran as the presidential candidate of Progressive Party in 1948. In 1947, Truman promulgated the Truman Doctrine, which called for the United States to prevent the spread of Communism through foreign aid to Greece and Turkey.