May 7, 1954 Vietnamese soldiers hoist their national flag after defeating the French at Dienbienphu, ending nearly a century of French colonial rule.

July 20, 1954 The Geneva Conference on Indochina declares a demilitarized zone at the 17th parallel, effectively partitioning Vietnam into the Communist North and the South.

1955 With U.S. backing, Ngo Dinh Diem organizes the Republic of Vietnam as an independent nation and declares himself president. President Dwight Eisenhower sends several hundred U.S. civilian and military advisers to assist Diem.

1959 North Vietnam creates a route along the Cambodian and Laotian borders to supply guerrilla forces in South Vietnam. It later becomes known as the Ho Chi Minh Trail.

July 8, 1959 Two U.S. military advisers are killed during a battle, becoming the first American casualties of the war.

1960 The National Liberation Front, dubbed "the Vietcong" by the Saigon regime, is founded in South Vietnam.

Jan. 12, 1962 The U.S. conducts its first combat mission against the Vietcong as Army helicopters ferry 1,000 South Vietnamese soldiers to sweep a Vietcong stronghold near Saigon.

May 4, 1964 The U.S. imposes a trade embargo on North Vietnam.

Aug. 2, 1964 The U.S. destroyer USS Maddox reports being fired on by a North Vietnamese torpedo boat in the Gulf of Tonkin. It reports being attacked again during a severe storm two days later. Both acts of North Vietnamese aggression have never been proven with sufficient evidence.

Aug. 7, 1964 Congress approves the Gulf of Tonkin Resolution, giving President Johnson extraordinary power to act in Southeast Asia - the functional equivalent of a declaration of war. American jets begin bombing North Vietnam later that month.

Feb. 24, 1965 Operation Rolling Thunder begins a sustained bombing offensive aimed at forcing North Vietnam to stop supporting Vietcong guerrillas in the south.

March 8, 1965 The first U.S. combat troops reach South Vietnam, landing in the coastal city of Danang.

June 27, 1965 Gen. William C. Westmoreland launches the first purely offensive operation by American ground forces in Vietnam, sweeping into Vietcong territory northwest of Saigon.

April 15, 1967 Demonstrators burn their draft cards during a protest in New York's Central Park. Domestic protests escalate as the number of U.S. troops in Vietnam approaches 500,000.

April - May 1967 U.S. air forces launch massive attacks against North Vietnamese airfields, destroying more than half of their air force.

September 1967 Nguyen Van Thieu is elected president of South Vietnam.

Jan. 30, 1968 The Vietcong launch the Tet offensive, attacking more than 100 cities and towns in South Vietnam. Although the offensive is a military failure for the North, the deaths of 2,500 Americans is a serious blow to domestic support for the war.

March 16, 1968 TIn the hamlet of Mylai, U.S. Charlie Company kills about 300 civilians, mostly women, children and elderly.

March 31, 1968 President Lyndon Johnson reverses his course on Vietnam, calling for a bombing halt and the pursuance of peace talks. At the end of his speech, he shocks a nationwide television audience by announcing that he will not run for another term.

February 1969 President Richard Nixon authorizes the bombing of North Vietnamese and Vietcong bases in Cambodia. U.S. forces drop more than a half million tons of bombs on Cambodia over the next four years.

April 1969 U.S. combat deaths in Vietnam exceed the 33,629 men killed in the Korean War.

Sept. 3, 1969 North Vietnamese leader Ho Chi Minh dies.

Nov. 15, 1969 An anti-war demonstration in Washington, D.C. draws 250,000 protestors.

April 30, 1970 The United States and South Vietnam invade Communist sanctuaries in Cambodia. This soldier wears a helmet declaring "Peace," an indicator of the mounting unpopularity of the war among U.S. troops.

May 4, 1970 Four students are killed by National Guardsmen during a protest at Kent State University in Ohio. Mary Ann Vecchio screams as she kneels by the body of a student lying face down.

March 30, 1972 More than 20,000 North Vietnamese troops cross the demilitarized zone, forcing the South Vietnamese units into a chaotic retreat. Here, a South Vietnamese marine carries a dead comrade.

Dec. 13, 1972 Peace talks between the United States and North Vietnam break off in Paris.

Dec. 18, 1972 Nixon orders a new bombing campaign against North Vietnam. U.S. aircraft drop more than 20,000 tons of bombs in the 12-day operation.

Jan. 27, 1973 The United States and North Vietnam sign the Paris Peace Accords, ending the American combat role in the war. The U.S. military draft ends.

March 29, 1973 The last U.S. combat troops leave Vietnam.

March 1975 North Vietnam sends 100,000 soldiers against Hue and Danang, and quickly overwhelms the northern provinces of South Vietnam.

April 21, 1975 Thieu resigns as South Vietnamese president and flees to Taiwan.

April 29, 1975 The last Americans are evacuated from Saigon. Flying from carriers off shore, U.S. helicopters coordinate a massive airlift that, within 18 hours, flies more than 1,000 American civilians and almost 7,000 South Vietnamese refugees out of Saigon.

April 30, 1975 7:52 a.m - The last helicopter lifts off from the roof of the U.S. Embassy, ending the mass evacuation.

April 30, 1975 10:30 a.m. - The last leader of South Vietnam, Gen. Duong Van Minh, announces on radio that the nation has surrendered.

April 30, 1975 12:45 p.m. - A 20-year-old female guerrilla named Nguyen Trung Kien raises the flag of the Vietcong's Provisional Revolutionary Government over the presidential palace, effectively ending the nation of South Vietnam.