#1 With no foundation to support itself, the civilian population was left to its own devices. Although American military and civilian forces kept working to defeat the communist insurgency, the slow-motion collapse of the South Vietnamese government doomed the counter-insurgency.
Except the indigenous Viet Cong were decimated in the Tet Offensive of 1968. After that the war was continued by North Vietnamese regulars with the intent of incorporation not liberation, much like the North Koreans did in 1950. The facade of an insurgency was gone.
When we withdrew the North Vietnamese launched a full out invasion of the south, which the South repulsed with American air support and material aid. Subsequently the Democratic controlled Congress cut off all aid funding, material assistance, and banned any direct military support. A second invasion was able to succeed. |