<P> There are several competing views on the conflict, with some on the North Vietnamese and National Liberation Front side viewing the struggle against U.S. forces as a colonial war and a continuation of the First Indochina War against forces from France and later on the United States, especially in light of the failed 1954 Geneva Conference calls for elections . Other interpretations of the North Vietnamese side include viewing it as a civil war especially in the early and later phases following the U.S. interlude between 1965 and 1970 as well as a war of liberation . The perspective of some Provisional Revolutionary Government of the Republic of South Vietnam, the successor to the Việt Cộng were motivated in part by significant social changes in the post-World War II Vietnam, and had initially seen it as a revolutionary war supported by Hanoi . The pro-government side in South Vietnam viewed it as a civil war, a defensive war against communism or were motivated to fight to defend their homes and families . The U.S. government viewed its involvement in the war as a way to prevent a communist takeover of South Vietnam . This was part of the domino theory of a wider containment policy, with the stated aim of stopping the spread of communism . </P> <P> Beginning in 1950, American military advisors arrived in what was then French Indochina . Most of the funding for the French war effort was provided by the U.S. The Việt Cộng, also known as Front national de libération du Sud - Viêt Nam or FNL (the National Liberation Front), a South Vietnamese communist common front aided by the North, fought a guerrilla war against anti-communist forces in the region, while the People's Army of Vietnam, also known as the North Vietnamese Army (NVA), engaged in more conventional warfare, and had launched armed struggles from 1959 onward . U.S. involvement escalated in 1960 under Kennedy, with troop levels gradually surging under the MAAG program, from just under a thousand in 1959 to 16,000 in 1963 . </P> <P> By 1964 there were already 23,000 U.S. troops involved, but this escalated further following the 1964 Gulf of Tonkin incident, in which a U.S. destroyer was alleged to have clashed with North Vietnamese fast attack craft . This was followed by the Gulf of Tonkin Resolution, which gave Lyndon B. Johnson authorization to increase U.S. military presence, deploying for the first time ground combat units and increasing troop levels to 184,000 . Every year onward there was significant build - up despite little progress, with Robert McNamara, one of the principle architects of the war begin to express doubts of victory by the end of 1966 . U.S. and South Vietnamese forces relied on air superiority and overwhelming firepower to conduct search and destroy operations, involving ground forces, artillery, and airstrikes . In the course of the war, the U.S. conducted a large - scale strategic bombing campaign against North Vietnam . Following the Tết Offensive, U.S. forces begun withdrawal under the Vietnamization phase, while Army of the Republic of Vietnam unconventional and conventional capabilities increased following a period of neglect and became modeled on heavy fire - power focused doctrines modeled after US forces . Operations crossed international borders: bordering areas of Laos and Cambodia were used by North Vietnam as supply routes and were heavily bombed by U.S. forces . </P> <P> 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 and begun the task of modernising their armed forces . Morale declined significantly among U.S. forces during the wind - down period and incidents of fragging, drug - use and insubordination increased with General Creighton Abrams remarking "I need to get this army home to save it". From 1969 onwards the military actions of the Việt Cộng insurgency decreased as the role and engagement of the NVA grew . Initially fielding less conventional and poorer weaponry, from 1970 onward the People's Army of Vietnam and its branch People's Liberation Armed Forces of South Vietnam had increasingly became mechanised and armoured, capable of modernised combined arms and mobile warfare and begun to widely deploy newer, untested weapons . These two sides would see significant, rapid changes throughout its lifetime from their original post-colonial armies, and by mid-1970s the ARVN became the fourth largest army with the PAVN became the fifth largest army in the world in two countries with a population of roughly 20 million each . </P>

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