The United States and the Soviet Union entered into a dangerous "arms race," in which each superpower began building and stockpiling as many nuclear weapons as possible to ensure its nuclear superiority.

In April 1961, 1,400 CIA-trained Cuban exiles attempted an invasion of Cuba by landing at the Bay of Pigs. The United States failed to give air support during the invasion and the Cuban were defeated. Even though the operation had been during Eisenhower's term, Kennedy took the blame for its failure.

Fidel Castro who was the leader of Cuba at the time, planned to strengthen his ties with the Soviet Union after the Bay of Pigs Invasion. The United States found out that Soviet nuclear bases were being built in Cuba so that the Soviet Union could launch an immediate attack on the United States. To prevent this from happening, President Kennedy sent a naval fleet to form a blockade around Cuba and threatened to invade if the missile plans were not called of. The Cuban Missile Crisis is seen as Kennedy's greatest foreign policy success.

In 1961, Khrushchev ordered the construction of the Berlin Wall which would seperate East and West Berlin. Kennedy promised to help West Berlin. In order to resist Communism, Kennedy created a special elite corps called the "Green Berets," who would be able to combat Communism through guerilla warfare.

In August 1964, President Johnson announced that the North Vietnamese had attacked American ships in international waters in the Gulf of Tonkin. In response to this alleged Gulf of Tonkin Incident, Congress passed the "Gulf of Tonkin Resolution," giving great power to the President to take all measures necessary to stop North Vietnamese aggression. Johnson saw this resolution as the legal basis for an esclation of war. Years later it was revealed that he had lied about the attack and that the American ships were the ones who attacked first.

Congress had given extroardinary power to President Johnson allowing him to go all out on North Vietnam, escalating the war.

By the beginning of 1968, American military leaders thought they had finally broken the power of the Vietcong. However, during the "Tet Offensive," which was launched on January 30th (the Vietnamese New Year), the Vietcong seized control of many of South Vietnam's major cities. Although American forces were eventually able to drive the Vietcong out of these strongholds, the offensive showed that the Communists were far from beaten. When the American commander in Vietnam asked for another 200,000 troops, President Johnson refused his request.

In 1973, Dr. Henry Kissinger proposed the Paris Peace Accords, a cease fire agreement with the North Vietnamese based on the withdrawel of all U.S. troops from Vietnam. Under the agreement, the United States was permitted to continue providing military and economic aid to South Vietnam.

Under Nixon's policy of "Vietnamization," the South Vietnamese assumed the brunt of the fighting. Nixon gradually withdrew American combat troops from Vietnam and ended the draft. At the same time, he increaed American bombing missions over the North and the flow of military supplies and economic support to South Vietnam.