Uh, dps, a Democratic President sent us to Nam, a Democratic President escalated the war there (meanwhile trying to convince the American people that he was doing just the opposite), but a Republican was in office when we finally got out. So, you might be slightly mistaken.
You are confusing liberal with democrat. Ending the war in Viet Nam was always a liberal idea. Starting and continuing the war was a conservative, pro business (oil, tin, rubber) idea.