At the height of the Cold War, tensions between the US and the USSR mounted on October 14, 1962 after an American U-2 spy plane passed over Cuba and gathered images of a Soviet SS-4 medium range ballistic missile. With a Soviet nuclear weapon only 90 miles from the Florida coast, President Kennedy marked this as a serious threat of nuclear war.
The following day, Kennedy convened the executive committee to deal with the diplomatic crisis, and communications with Soviet leader Nikita Khrushchev began. Khrushchev claimed the installation of the missiles were in response to the presence of American nuclear weapons in Western Europe and Turkey, as well as American aggression against communist Cuba. To prevent Soviet ships from transporting more weapons and supplies, Kennedy implemented a Navy blockade around the island.
On October 22, Kennedy informed the American people of the crisis, and a sense of doom enveloped the country. This tension increased when, on October 24, Soviet ships approached the Navy blockade. However, they made no attempt to breech, and military action was avoided.
Tension reached its height when an American reconnaissance plane piloted by Major Rudolf Anderson was shot down over Cuba, making him the first and only casualty during the crisis. In response to this, an invasion force was gathered in Florida and prepared to invade Cuba. However, Kennedy and Khrushchev reached an agreement. If the US made no further aggressive actions toward Cuba and removed their nuclear weapon placed in Turkey, the the USSR would dismantle the missiles on Cuba.
No amount of diplomacy prevented the Vietnam War, however.
After nearly a century of colonial rule, France began to lose its grip on Indochina when Germany invaded the country during WWII. With France weakened, Japan invaded its holdings in Southeast Asia. In May of 1941, Ho Chi Minh created the Indochinese Communist Party and established the Viet Minh as a force to fight French and Japanese occupation.
Near the end of WWII, Japanese forces overthrew what was left of the French colonial power and declared independence for Vietnam, Cambodia, and Laos. However, once the war was over and the Germans driven out, France attempted to reassert its power in the region. In September 1945, Ho Chi Minh declared an independent North Vietnam, and guerrilla warfare against the French began.
Allies with France, the US implemented the Truman Doctrine. This stated that the US was obligated to aid any country whose stability was threatened by communism. This marked the beginning of American involvement in the war. In January of 1950, the Peoples Republic of China and the Soviet Union began giving economic and military aid to communist forces in the north. In response, the US gave military assistance to French forces in the south.
In early 1954, the war turned in favor of the communist forces when the French were defeated at Dien Bien Phu. It was then Eisenhower gave a speech discussing the "domino effect" of communism in Southeast Asia, providing a justification for future US military actions. In July, the Geneva Accords resulted in the official divide of North and South Vietnam at the 17th parallel.
In May 1959, northern forces began building the Ho Chi Minh Trail, a supply route through Laos and Cambodia used to support guerrilla attacks against the South Vietnamese government of Ngo Dinh Diem established by the US. In July, the first US soldiers killed in the conflict lost their lives in a Viet Cong raid on Saigon. In May 1961, President Kennedy authorized secret operations against the Viet Cong.
With tensions in the south due to the Diem government, the US supported a military coup in November 1963, which resulted in the death of Ngo Dinh Diem and his brother. The following summer, USS Maddox was allegedly attacked in the Gulf of Tonkin. This resulted in the Gulf of Tonkin Resolution and the entry of the US into the conflict. The Vietnam War was in full swing with all players present. What resulted was one of the bloodiest conflicts in human history.