See response below.
North.
At the end of the war.
North won.
The North won and the South lost in both undeclared wars; US Civil War & Vietnam.
North Vietnam won South Vietnam by conquering it.
Vietnam won the French war. North Vietnam won the American Vietnam War. There was no such country named "Vietnam" during the American Vietnam War 1955-1975. There were two nations: North VN & South VN.
The North won, the South lost.
north viet nam, you cannot fight a limited war and win, as is going on in Iraq presently.
This is the main one- South Vietnam and its supporters were not sufficient enough to defeat Communist North Vietnam, who had the help of China and other Communist countries. So the South was defeated, the North took over the South and combined South and North into one country, Vietnam. Due to the whole country becoming Communist many South Viets fled the country as refugees.
Preserving the Republic of South Vietnam from being conquered by Communist North Vietnam.
The North won.
North Vietnam won the war when their tanks crashed thru the South's government gates on 30 April 1975.
North Vietnamese won the Vietnam War, and it is the year 1975, not 1990, that they militarily defeat South Vietnam.