Truman authorized the first and only use of nuclear weapons in war against Hiroshima and Nagasaki in Japan. Truman's administration engaged in an internationalist foreign policy by working closely with British Prime Minister Clement Attlee. Truman staunchly denounced isolationism. He energized the New Deal coalition during the 1948 presidential election and won a surprise victory against Republican Thomas E. Dewey that secured his own presidential term.
Truman presided over the onset of the Cold War in 1947. He oversaw the Berlin Airlift and Marshall Plan in 1948. With the involvement of the US in the Korean War of 1950–1953, South Korea repelled the invasion by North Korea. Domestically, the postwar economic challenges such as strikes and inflation created a mixed reaction over the effectiveness of his administration. In 1948, he proposed Congress pass comprehensive civil rights legislation. Congress refused, so in 1948 Truman issued Executive Order 9980 and Executive Order 9981 which desegregated the armed forces and federal agencies.
Corruption in the Truman administration became a central campaign issue in the 1952 presidential election. He was eligible for reelection in 1952, but with weak polls he decided not to run. Republican Dwight D. Eisenhower attacked Truman's record and won easily. 