Vietnam War

Beginning in 1950, American military advisors arrived in what was then French Indochina. U.S. involvement escalated in the early 1960s, with troop levels tripling in 1961 and again in 1962. U.S. involvement escalated further following the 1964 Gulf of Tonkin incident, in which a U.S. destroyer clashed with North Vietnamese fast attack craft, which was followed by the Gulf of Tonkin Resolution, which gave the U.S. president authorization to increase U.S. military presence. Regular U.S. combat units were deployed beginning in 1965. Operations crossed international borders: bordering areas of Laos and Cambodia were heavily bombed by U.S. forces as American involvement in the war peaked in 1968, the same year that the communist side launched the Tet Offensive. The Tet Offensive failed in its goal of overthrowing the South Vietnamese government, but became the turning point in the war, as it persuaded a large segment of the U.S. population that its government's claims of progress toward winning the war were illusory despite many years of massive U.S. military aid to South Vietnam.
Gradual withdrawal of U.S. ground forces began as part of "Vietnamization", which aimed to end American involvement in the war while transferring the task of fighting the Communists to the South Vietnamese themselves. Despite the Paris Peace Accord, which was signed by all parties in January 1973, the fighting continued. In the U.S. and the Western world, a large anti-Vietnam War movement developed as part of a larger counterculture. The war changed the dynamics between the Eastern and Western Blocs, and altered North–South relations. https://en.wikipedia.org/wiki/Vietnam_War
Direct U.S. military involvement ended on 15 August 1973. The capture of Saigon by the North Vietnamese Army in April 1975 marked the end of the war, and North and South Vietnam were reunified the following year. The war exacted a huge human cost in terms of fatalities (see Vietnam War casualties). Estimates of the number of Vietnamese soldiers and civilians killed vary from 800,000 to 3.1 million. Some 200,000–300,000 Cambodians, 20,000–200,000 Laotians, and 58,220 U.S. service members also died in the conflict, with a further 1,626 missing in action.