The Vietnam War was never declared - Nixo-facto, the Vietnam war never happened. What really happened was that John F. Kennedy sent advisors into Vietnam to help them with a border dispute. Over the course of a few years, more and more advisors were needed and eventually the border dispute was ended. Now some people call this a "war" but in reality, it was just America helping a defenseless country in the way only America can. Some people say the Vietnam war was a mistake - probably because there is no oil in Vietnam. Who knew?
If Stephen Colbert, the most powerful man on Earth, wanted to, he could declare the Vietnam War to be real.