“Why have the Americans not made a fuss about the fact that more than 100,000 Chinese troops help you building the railways, roads and airports although they knew about it?” 
- - Chairman Mao to Vietnamese Premier Dong, 1970
In conclusion, as we can see from the considerable historical material outlined above, the military support provided by the People’s Republic of China, to include advisors, equipment and combat troops, was the decisive factor for the Communist Democratic Republic of Vietnam prevailing during 1949-1975 in both the First and Second Vietnam Wars. The small arms, mortars, ammunition, uniforms, tanks, artillery, radars, anti-aircraft guns, jet aircraft, trucks, and naval vessels were critical in the North Vietnamese struggle. However, what was even more critical and normally not acknowledged in the laundry list of war material is the psychological and strategic advantage provided by Communist China’s pledge to intervene in the advent of a United States invasion of North Vietnam, and communicating that pledge to the U.S. This strategic advantage in effect cannot be overstated.
As General Westmoreland’s former G-2, or Intelligence Officer would write after the Vietnam Wars “With a friendly China located adjacent to North Vietnam, there would have been little chance for a Vietnamese victory against the French, and later against the Americans and South Vietnamese.”  It is rather ironic that most professional historians tend to downplay or ignore China’s decisive role in North Vietnam’s victory while the military and intelligence communities, U.S. at least, are much more willing to acknowledge this fact. Perhaps this is understandable since if one acknowledges the role played by China it calls into question such Vietnam myths as the “poorly armed guerrilla” and the “military genius” of Giap, among other issues. Historians such as Xiaoming Zhang and Qiang Zhai are challenging the paradigm of accepted Vietnam history and in doing so are performing a great service.
“Thus the highest realization of warfare is to attack the enemy plans;” according to the learned military theorist Sun-Tzu in the Art of War.  In respects this is exactly what the North Vietnamese, and Chinese did in both Vietnam Wars: they successfully attacked the Western powers war plans. The considerable support for the DRV by the PRC, to include a promise to intervene with massive numbers of troops in the event of an invasion of North Vietnam, effectively eliminated this course of action, and perhaps others, as potential war winning options for the West. Thus, with the support of China, on a strategic level of war the DRV was able to remain upon the offensive throughout the war, maintaining the initiative and finally achieving victory as Saigon fell in April of 1975.