Beginning in 1950, American military advisors arrived in what was then French Indochina.[87][A 3] 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.

 

Direct U.S. military involvement ended on 15 August 1973 as a result of the Case-Church Amendment passed by the U.S. Congress. 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 966,000 to 3.8 million. Some 275,000–310,000 Cambodians, 20,000–62,000 Laotians,  and 58,220 U.S. service members also died in the conflict, and a further 1,626 remain missing in action.  The Sino-Soviet split re-emerged following the lull during the Vietnam War and ties between the DRV and its Cambodian allies in the Royal Government of the National Union of Kampuchea, the newly-formed Democratic Kampuchea begun almost immediately in a series of border raids by the Khmer Rouge and erupted into the Cambodian–Vietnamese War, with Chinese forces directly intervening in the Sino-Vietnamese War. The end of the war and resumption of the Third Indochina War would precipitate the Vietnamese boat people and the bigger Indochina refugee crisis, which saw an estimated 250,000 people perish at sea.