The Vietnam War, also known as the Second Indochina War, and in Vietnam as the Resistance War Against America or simply just the American War, was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam and South Vietnam. North Vietnam was supported by the Soviet Union, China, and other communist allies; South Vietnam was supported by the United States, South Korea, the Philippines, Australia, Thailand, and other anti-communist allies. The war, considered a Cold War-era proxy war by some, lasted 19 years, with direct U.S. involvement ending in 1973, and included the Laotian Civil War and the Cambodian Civil War, which ended with all three countries becoming communist in 1975.
The scale of fighting was enormous, by 1970, the ARVN was the world's fourth-largest army, with the PAVN being similar in size at around a million regular soldiers. The war exacted a huge human cost in terms of fatalities, estimates of the number of Vietnamese soldiers and civilians killed vary from 966,000 to 3.8 million. Some 275,000 to 310,000 Cambodians, 20,000 to 62,000 Laotians, and 58,220 U.S. service members also died in the war, and a further 1,626 remain missing in action.
The Sino-Soviet split re-emerged following the lull during the Vietnam War. The conflict between North Vietnam and its Cambodian allies in the Royal Government of the National Union of Kampuchea, and the newly-formed Democratic Kampuchea began almost immediately in a series of border raids by the Khmer Rouge, eventually escalating into the Cambodian–Vietnamese War. Chinese forces directly invaded Vietnam in the Sino-Vietnamese War, with subsequent border conflicts lasting until 1991. Insurgencies were fought by the unified Vietnam in all three countries. The end of the war and resumption of the Third Indochina War would precipitate the Vietnamese boat people and the larger Indochina refugee crisis, which saw millions of refugees leave Indochina (mainly southern Vietnam), with an estimated 250,000 of whom perished at sea. Within the U.S, the war gave rise to what was referred to as Vietnam Syndrome, a public aversion to American overseas military involvements, which together with the Watergate scandal contributed to the crisis of confidence that affected America throughout the 1970s
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