1940s: The United States became involved in World War II in 1941 after the bombing of Pearl Harbor. The war ended the Great Depression as well as American isolationism. The United States government's fear of the Soviet Union as a major communist force marked the beginning of the Cold War.

1960s: The United States became involved in several international conflicts, including the 1961 Bay of Pigs invasion in Cuba, the Cuban Missile Crisis in 1962, and the Vietnam War beginning in 1965. Low public opinion of American involvement in Vietnam was marked by protests across the country, especially on college campuses. In 1968, United States involvement hit its peak with approximately 500,000 troops in Vietnam. Approximately 58,000 United States troops were killed in the war.

Today: Foreign relations in the 1990s have been marked by the fall of communism in Russia and Eastern Europe, heralding the end of the Cold War...