| •1938 | House Un-American Activities Committee (HUAC) established |
| •1945 | Potsdam Conference |
| •1946 | Kennan telegram outlines containment strategy |
| Churchill's “iron curtain” speech |
| •1947 | Truman Doctrine articulated |
| National Security Act passed; Central Intelligence Agency (CIA) established |
| Truman creates Federal Employee Loyalty Program |
| •1948–1949 | Berlin blockade and airlift |
| Alger Hiss affair |
| •1948 | Marshall Plan approved |
| •1949 | National Security Agency established |
| Communists win Chinese civil war |
| North Atlantic Treaty Organization (NATO) formed |
| Soviet Union successfully tests atomic weapon |
| •1950–1953 | Korean War |
| •1950–1954 | McCarthy's anti-Communist crusade |
| •1950 | NSC-68 issued |
| •1953 | Julius and Ethel Rosenberg executed for espionage |
| U.S. supports overthrow of Iranian government |
| •1954 | French defeated in Vietnam |
| U.S. supports overthrow of Guatemalan government |
| •1955 | U.S. supports Ngo Diem in South Vietnam |
| •1956 | Suez crisis |
| •1958 | U.S. troops sent to Lebanon |
| •1959 | Fidel Castro takes power in Cuba |
| The Vietcong formed |
| •1961 | U.S. intervenes in the Congo |