MwRYum
Major
The fact is Vietnam won against China in Sino-Vietnamese War in 1979.
For one, both side declared they are the victors...Chinese aim to give Vietnam a border war (and by Chinese account, retrieved all the stuff they gave Vietnam as aid during the Vietnam War) and the border disputes; Vietnam was of course claimed they beat back yet another invasion.
But in the long run, the Sino-Vietnamese War and the subsequent conflicts into the 80s bleed the Vietnam bad in terms of economy and men (there's a reason why at a time Vietnam had to export brides), then when the USSR (Vietnam's backer) folded both sides finally stopped fighting.
Then when you look at the areas they conducted battles in and the battle orders, it was a predominantly infantry war due to the very difficult terrain.