The Cold War began as a conflict between the United States and the Soviet Union over Eastern Europe and the fate of post-World War II Germany. Early in the conflict, the United States adopted a strategy of containment, which quickly expanded to Asia after China became a communist state under Mao Zedong. The first effect of that expansion was the Korean War, after which, under Dwight D. Eisenhower, containment of communism became America’s guiding principle across the developing world — often called the Third World. Cold War tensions relaxed in the late 1950s but erupted again under John F. Kennedy with the Cuban missile crisis, the building of the Berlin Wall, and major increases in American military assistance to South Vietnam. Cold War imperatives between 1945 and the early 1960s meant a major military buildup, a massive nuclear arms race, and unprecedented entanglements across the globe.

On the domestic front, Harry S. Truman started out with high hopes for an expanded New Deal, only to be confounded by resistance from Congress and the competing demands of the Cold War. The greatest Cold War-inspired development was a climate of fear over internal subversion by Communists that gave rise to McCarthyism. Truman’s successor, Eisenhower, brought the Republicans back into power. Although personally conservative, Eisenhower actually proved a New Dealer in disguise. When Eisenhower left office and Kennedy became president, it seemed that a “liberal consensus” prevailed, with old-fashioned, laissez-faire conservatism mostly marginalized in American political life.