The history of the United States from 1945 to 1964 was a time of high economic growth and general prosperity. It was also a time of confrontation as the capitalist United States and its allies politically opposed the Soviet Union and other communist states; the Cold War had begun. African Americans united and organized, and a triumph of the civil rights movement ended Jim Crow segregation in the Southern United States.James T. Patterson, Grand Expectations: The United States, 1945–1974 (1988) pp 771-90 Further laws were passed that made discrimination illegal and provided federal oversight to guarantee voting rights.

In the period, an active foreign policy was pursued to help Western Europe and Asia recover from the devastation of World War II. The Marshall Plan helped Western Europe rebuild from wartime devastation. The main American goal was the Containment of communism. An arms race escalated through increasingly powerful nuclear weapons. The Soviets formed the Warsaw Pact of European satellites to oppose the American-led North Atlantic Treaty Organization (NATO) alliance. The U.S. fought a bloody, inconclusive war in Korea and was escalating the war in Vietnam as the period ended. Fidel Castro took power in Cuba, and when the USSR sent in nuclear missiles to defend it, the Cuban Missile Crisis of 1962 was triggered with the U.S., the most dangerous point of the era.Alan P. Dobson and Steve Marsh, US foreign policy since 1945 (2006) pp 18-29, 76-90

On the domestic front, after a short transition, the economy grew rapidly, with widespread prosperity, rising wages, and the movement of most of the remaining farmers to the towns and cities. Politically, the era was dominated by liberal Democrats who held together with the New Deal Coalition: Franklin D. Roosevelt (1933–1945), Harry S. Truman (1945–1953), John F. Kennedy (1961–1963) and Lyndon Johnson (1963–1969). Republican Dwight D. Eisenhower (1953–1961) was a moderate who did not attempt to reverse New Deal programs such as regulation of business and support for labor unions; he expanded Social Security and built the interstate highway system. For most of the period, the Democrats controlled Congress; however, they were usually unable to pass as much liberal legislation as they had hoped because of the power of the Conservative Coalition. The Liberal coalition took control of Congress after Kennedy's assassination in 1963, and launched the Great Society.Alonzo L. Hamby, Liberalism and Its Challengers: From F.D.R. to Bush (2nd ed. 1992) pp 52-139

This period of Post–World War II economic expansion witnessed the rapid growth of suburbs and a growing middle class.

Cold War

The Cold War (1945–1991) was the continuing state of political conflict, military tension, and economic competition between the Soviet Union and its satellite states, and the powers of the Western world, led by the United States. Although the primary participants' military forces never officially clashed directly, they expressed the conflict through military coalitions, strategic conventional force deployments, a nuclear arms race, espionage, proxy wars, propaganda, and technological competition, e.g., the Space Race.

Origins While the United States and Soviet Union remained Allies throughout World War II, diplomatic relations were nonetheless tense. The Western Allies feared that the Soviet Union would establish hegemony over the territories it had seized from Germany on the Eastern Front. President Roosevelt believed that the countries liberated from the Axis Powers should be given self-determination to choose their own governments; at the Yalta Conference in February 1945, the Western Allied leaders pressed Soviet leader Joseph Stalin to allow Soviet-occupied countries to hold elections. Meanwhile, Stalin's insistences that the Soviet Union expand its borders westward increased the suspicions of the Western Allies. The Soviet Union did not withdraw from Eastern Europe after the war was over, and established its own puppet governments in the territory it had occupied.

While Roosevelt was confident he could cooperate with Stalin after the war, Truman was much more suspicious. The United States provided large-scale grants to Western Europe under the Marshall Plan (1948–1951), leading to a rapid economic recovery. The Soviet Union refused to allow its satellites to receive American aid. Instead, the Kremlin used local communist parties, and the Red Army, to control Eastern Europe in totalitarian fashion.Anne Applebaum, Iron Curtain: The Crushing of Eastern Europe, 1944–1956 (2012) p. xxii - xxv. Britain, in deep financial trouble, could no longer support Greece in its civil war with the communists. It asked the United States to take over aid to Greece. With bipartisan support in Congress, Truman responded with the Truman Doctrine in 1947. Truman followed the intellectual leadership of the State Department, which called for containment of Soviet communist expansion. The hope was that internal contradictions, such as diverse nationalism, would ultimately undermine Soviet ambitions.Carole K. Fink, Cold War: An International History (2013) pp 53-79.

By 1947, the Soviets had fully absorbed the three Baltic nations, and effectively controlled Poland, East Germany, Czechoslovakia, Romania, and Bulgaria. Austria and Finland were neutral and demilitarized. The Kremlin did not control Yugoslavia, which had a separate communist regime under Marshall Tito; They had a permanent bitter break in 1948. The Cold War lines stabilized in Europe along the Iron Curtain, and there was no fighting. The United States helped form a strong military alliance in NATO in 1949 including most of the nations of Western Europe, and Canada. In Asia, however, there was much more movement. The United States failed to negotiate a settlement between its ally, nationalist China under Chiang Kai-shek, and the communists under Mao Zedong. The communists took over China in 1949 and the nationalist government moved to the offshore island of Formosa (Taiwan), which came under American protection. Local communist movements attempted to take over all of Korea (1950) and Vietnam (1954). Communist hegemony covered one third of the world's land while the United States emerged as the world's more influential superpower, and formed a worldwide network of military alliances.John Lewis Gaddis, The Cold War: A New History (2006) pp 31-95

There were fundamental contrasts between the visions of the United States and the Soviet Union, between capitalist democracy and totalitarian communism. The United States envisioned the new United Nations as a Wilsonian tool to resolve future troubles, but it failed in that purpose. The U.S. rejected totalitarianism and colonialism, in line with the principles laid down by the Atlantic Charter of 1941: self-determination, equal economic access, and a rebuilt capitalist, democratic Europe that could again serve as a hub in world affairs.Townsend Hoopes and Douglas Brinkley, FDR and the Creation of the U.N. (2000) pp 205-22

Containment

For NATO, containment of the expansion of Soviet influence became foreign policy doctrine; the expectation was that eventually the inefficient Soviet system would collapse of internal weakness, and no "hot" war (that is, one with large-scale combat) would be necessary. Containment was supported by Republicans (led by Senator Arthur Vandenberg of Michigan, Governor Thomas Dewey of New York, and general Dwight D. Eisenhower), but was opposed by the isolationists led by Senator Robert A. Taft of Ohio.

1949–1953 In 1949, the communist leader Mao Zedong won control of mainland China in a civil war, established the People's Republic of China, then traveled to Moscow where he negotiated the Sino-Soviet Treaty of Friendship, Alliance and Mutual Assistance. China had thus moved from a close ally of the U.S. to a bitter enemy, and the two fought each other starting in late 1950 in Korea. The Truman administration responded with a secret 1950 plan, NSC 68, designed to confront the communists with large-scale defense spending. The Russians had built an atomic bomb by 1949, much sooner than expected. Truman then ordered the development of the hydrogen bomb. Two of the spies who gave atomic secrets to Russia were tried and executed.

France was hard-pressed by communist insurgents in the First Indochina War. The U.S. in 1950 started to fund the French effort on the proviso that the Vietnamese be given more autonomy.

Korean War

Stalin approved a North Korean plan to invade U.S.-supported South Korea in June 1950. President Truman immediately and unexpectedly implemented the containment policy by a full-scale commitment of American and UN forces to Korea. He did not consult or gain approval of Congress but did gain the approval of the United Nations (UN) to drive back the North Koreans and re-unite that country in terms of a rollback strategy.The Soviets were boycotting the UN at that time (because it would not admit the People's Republic of China) and so was not present to veto Truman's actions. While originally a civil war, it quickly escalated into a proxy war between the United States and its allies and the communist powers of the People's Republic of China and the Soviet Union.

After a few weeks of retreat, on September 15 General Douglas MacArthur conducted an amphibious landing at the city of Inchon (Song Do port).Bill Sloan, The Darkest Summer: Pusan and Inchon 1950: The Battles That Saved South Korea—and the Marines—From Extinction(2009) The North Korean army collapsed, and within a few days, MacArthur's army retook Seoul (South Korea's capital). He then pushed north, capturing Pyongyang in October. This advantage was lost when hundreds of thousands of Chinese entered an undeclared war against the United States and pushed the US/UN/Korean forces back to the original starting line, the 38th parallel.

MacArthur planned for a full-scale invasion of China, but this was against the wishes of President Harry S. Truman and others who supported a ceasefire and UN withdrawal from Korea. As a result, Truman relieved MacArthur of command, replacing him with general Matthew Ridgway, who de-escalated the fighting to allow for a peace deal to be made. Dwight D. Eisenhower in 1952 campaigned against Truman's failures of "Korea, Communism and Corruption," promising to go to Korea himself and end the war. By threatening to use nuclear weapons in 1953, Eisenhower ended the war with a truce that is still in effect.Spencer Tucker, ed. The Encyclopedia of the Korean War (3 vol 2010)

An armistice agreement was finally agreed to by the United Nations Command, the Korean People's Army, and the Chinese People's Volunteer Army on July 27, 1953. The war left 33,742 American soldiers dead, 92,134 wounded, and 80,000 missing in action (MIA) or prisoner of war (POW). Estimates place Korean and Chinese casualties at 1,000,000–1,400,000 dead or wounded, and 140,000 MIA or POW. According to Chalmers Johnson, the death toll is 14,000–30,000

Vietnam War