Astonishingly to anyone past 40, millions of Americans don't. Nearly half the population was unborn, or not yet out of grade school, when U.S. troops left there almost 20 years ago.
And considering what's happening in Washington and the Persian Gulf, there seem to be important others who are old enough to recall Vietnam but don't.
One 76-year-old who remembers it and its lessons well is retired now, living down South. His name is William C. Westmoreland. Just as when he was commander of U.S. forces in Vietnam and later Army chief of staff, he observes protocol today and refuses publicly to second-guess the politicians who have to make decisions about war or peace.
But what he has already said, based on his own hard experience, applies directly to Washington's current flirtation with war against Iraq. The last previous time I discussed foreign interventions with him was during Ronald Reagan's period of rage over what was happening not in the Middle East, but in Central America.
"The cardinal lesson of Vietnam is that we can't send troops to war and expect them to make good any foreign commitment unless American public opinion is behind it," he said. He wished Lyndon Johnson had submitted the U.S. presence in Vietnam to annual review and reaffirmation by Congress. "We could have had a decision as early as 1966 to pull out."
In our democracy, one man's vote is as good as any other's, but one man's opinion may weigh more than a million others. In this case, the reservations expressed by experts are increasingly held by Americans at large.
Three months ago, 82 percent of those questioned in a USA Today poll approved of George Bush's response to the Persian Gulf situation. This week, after the president's announcement of massive new reinforcements going to the Middle East, that figure was down to 51 percent.
My own memory of Vietnam and how we got into it is as sharp as if it all happened yesterday. I can compare this fall to the winter of 1964-65, when Johnson responded to General Westmoreland's urgent calls for reinforcements and started turning that fight into an American war.
In February, 1965, the president ordered the first U.S. bombing strikes against North Vietnam. That month, polls showed 83 percent of the public supported him. The only audible objectors were early doves: in the Senate, George McGovern and Frank Church were for negotiations, and Wayne Morse and Ernest Gruening were lonely in their calls for U.S. withdrawal.
There are differences between 1965 and today, but also eerie similarities: then, Senate hawks issued a statement saying, "So long as there is communist-promoted infiltration of South Vietnam...there can be no negotiations." But an unnamed diplomat was more frank. While the public U.S. position was against negotiations, he said, "We hate to appear so stringent. It's a real dilemma."
It's a real dilemma today, too, as Mr. Bush keeps raising the stakes with his "I'm fed up" rhetoric while every diplomat in town wishes he would leave some room for deal-cutting. It's understood that the troop buildup is intended first as bluff, to make Saddam Hussein see he can't win a war, but that strategy loses effectiveness when it is publicly proclaimed to the world. Once close to half a million troops are in place, it will be hard for Mr. Bush after all his bluster to bring them home without complete capitulation by Iraq.
It doesn't take a professional like General Westmoreland to see TTC that. The roster of those cautioning the president today is far longer and politically mixed than that little caucus of Democratic doves in 1965.
This time, it includes pro-defense Democrats like Sam Nunn, who says "the last thing we need is to have...a bloody war, and have American boys being sent and brought back in body bags and yet not have the American people behind them." It includes thoughtful Republicans like Dick Lugar, who says the president has to do a better job of explaining what we are doing in the Gulf. It includes Medal of Honor winners, and GOP pollsters, and people up and down my street and yours.
Teen-age Americans, and some still on a high from the easy Eighties, may think war means a quick strike like those at Grenada, Libya and Panama. Older heads know better. History shows that those urging Mr. Bush to go slow -- refine his objectives, give the embargo on Iraq time to work -- are doing him a great favor. If he listens, he will do himself one, and cool it.