Harry S. Truman (May 8, 1884 – December 26, 1972) was the 33rd President of the United States (1945–1953). As the 34th vice president, he succeeded Franklin D. Roosevelt, who died less than three months after he began his fourth term.

During World War I Truman served as an artillery officer, making him the only president to have seen combat in World War I (his successor Eisenhower spent the war training tank crews in Pennsylvania). After the war he became part of the political machine of Tom Pendergast and was elected a county commissioner in Missouri and eventually a United States senator. After he gained national prominence as head of the wartime Truman Committee, Truman replaced vice president Henry A. Wallace as Roosevelt's running mate in 1944.

Truman faced challenge after challenge in domestic affairs. The disorderly reconversion of the economy of the United States was marked by severe shortages, numerous strikes, and the passage of the Taft-Hartley Act over his veto. He confounded all predictions to win re-election in 1948, helped by his famous Whistle Stop Tour of rural America. After his re-election he was able to pass only one of the proposals in his Fair Deal program. He used executive orders to begin desegregation of the U.S. armed forces and to create loyalty checks which dismissed thousands of communist supporters from office, even though he strongly opposed mandatory loyalty oaths for governmental employees, a stance that led to charges that his administration was soft on communism. Truman's presidency was also eventful in foreign affairs, with the end of World War II and his decision to use nuclear weapons against Japan, the founding of the United Nations, the Marshall Plan to rebuild Europe, the Truman Doctrine to contain communism, the beginning of the Cold War, the creation of the North Atlantic Treaty Organization, and the Korean War. Corruption in Truman's administration reached the cabinet and senior White House staff. Republicans made corruption a central issue in the 1952 campaign.