When America joined the Vietnam war Timeline
The US Enters the Fray
1964 - Gulf of Tonkin incident: the US says North Vietnamese patrol boat fire on two US Navy destroyers. US Congress approves Gulf of Tonkin Resolution, authorizing military action in the region.
1965 - 200,000 American combat troops arrive in South Vietnam.
1966 - US troop numbers in Vietnam rise to 400,000, then to 500,000 the following year.
1968 - Tet Offensive - a combined assault by Viet Cong and the North Vietnamese army on US positions - begins. More than 500 civilians die in the US massacre at My Lai. Thousands are killed by communist forces during their occupation of the city of Hue.
1969 - Ho Chi Minh dies. President Nixon begins to reduce US ground troops in Vietnam as domestic public opposition to the war grows.
1970 - Nixon's national security advisor, Henry Kissinger, and Le Duc Tho, for the Hanoi government, start talks in Paris.
1973 - Ceasefire agreement in Paris, US troop pull-out completed by March
1975 - North Vietnamese troops invade South Vietnam and take control of the whole country after South Vietnamese President Duong Van Minh surrenders.
These were the important events that took place during the time that America entered the Vietnam war as well as the date and year that it took place.
Refernce
https://www.bbc.com/news/world-asia-pacific-16568035