The Second Indochina War, commonly known as the Vietnam War, pitted the recently successful Communist Vietnam People's Army (VPA or PAVN, but also incorrectly known as the North Vietnamese Army or NVA) and the National Front for the Liberation of Vietnam (South Vietnamese NLF guerrilla fighters allied with the PAVN, known in the Republic of Vietnam as the Viet Cong, meaning 'Communists Traitor to Vietnam')[2] against United States troops and the United States-backed ARVN (Republic of Vietnam soldiers).
Because there was no declaration of war, there is much disagreement as to when the war began, but two events commonly cited are the first arrival of United States advisors in South Vietnam in 1955, and open declaration of United States involvement in 1964. During the War, the North Vietnamese transported most of their supplies via the Ho Chi Minh Trail (known to the Vietnamese as the Truong Son Trail, after the Truong Son mountains), which ran through Laos and Cambodia. As a result, the areas of these nations bordering Vietnam would see heavy combat during the war.
For the United States, the political and combat goals were ambiguous: success and progress were ill-defined and, along with the large numbers of casualties, the Vietnam War raised moral issues that made the war increasingly unpopular at home. U.S. news reports of the 1968 Tet offensive, especially from CBS, were unfavorable in regard to the lack of progress in ending the war. Although the 1968 Tet offensive resulted in a military victory for South Vietnam and the United States, with virtually complete destruction of the NLF forces combat capability, it was, by the intensity of the combats, the contradiction it implied with recent reports of withdrawals of US troops and status of the war,[3] also a turning point in American voter opposition to U.S. support for their Cold War Vietnamese allies.
The United States began withdrawing troops from Vietnam in 1970, with the last troops returning in January, 1973. The Paris Peace Accords called for a cease-fire, and prohibited the North Vietnamese from sending more troops into South Vietnam - although the North Vietnamese were permitted to continue to occupy those regions of South Vietnam they had conquered in the 1972 Easter Offensive.
The North Vietnamese never intended to abide by the agreement. Fighting continued sporadically through 1973 and 1974, while the North Vietnamese planned a major offensive, tentatively scheduled for 1976. The North Vietnamese Army in South Vietnam had been ravaged during the Easter offensive in 1973, and it was projected that it would take until 1976 to rebuild their logistical capabilities.
The withdrawal had catastrophic effects on the South Vietnamese Army (ARVN). Shortly after the Paris Peace Accords, the United States Congress made major budget cuts in military aid to the South Vietnamese. The ARVN, which had been trained by American troops to use American tactics, quickly fell into disarray. Although it remained an effective fighting force throughout 1973 and 1974, by January 1975 it had disintegrated. The North Vietnamese hurriedly attacked the much weakened South, and met with little resistance.
Saigon, the capital of South Vietnam, was taken by the PAVN on April 30, 1975, and the Second Indochina War ended.
The fighting that took place between North and South Vietnam following United States withdrawal is sometimes called the Third Indochina War; this term usually refers to a later 1979 conflict, however (see below).