Three years ago, as we were ending our disastrous war in Iraq, Barack Obama, who first emerged on the national scene by warning against it as a purposeless folly, praised it as a partnership for freedom and democracy with the Iraqi people. I gagged in disgust; perhaps you did too.

Presidents, like the rest of us, often eat their own words, but not usually when they were the right ones to begin with. Barack Obama did more than replace the truth he’d once told about Iraq with a lie; he replaced it with a myth.

The myth is that we fight our wars only for the most noble, disinterested and high-minded reasons, and under the most necessary circumstances. That war, for us, is both a reluctant calling and a sacred cause. That is a lie, one that undergirds American militarism in general.

The trouble with a lie is that sooner or later it requires other ones to defend it. The problem with a myth is that it covers everything with a lie. Obama didn’t articulate the myth of American righteousness back in 2011, but he left it as an inescapable inference.

If a war as discredited and reviled as the one in Iraq, a war itself built on the most deliberate and egregious of lies, was really a fine and principled thing, then which war we could fight would not be?

The other shoe was bound to drop, and it has. The Obama administration is now trying to sanitize the Vietnam War. It is hard to imagine a more unpromising project, but $15 million of your tax have been already gone into it. The price tag in historical truth will be far higher.

The occasion is what is billed as the 50th anniversary of the war. It’s hard to put a precise entry date on it, because we were supporting France’s efforts to hold on to its restored colony in Vietnam from 1946 on, supplanted it as a colonial power in 1954 and had “advisors” deployed from that time on to support the puppet government we created in South Vietnam.

By the time of the Kennedy administration we were already vested in fighting the wrong side of a civil war. If you want a peg to hang the full-fledged conflict on, it might be the alleged attack on the USS Turner Joy, a destroyer off the coast of North Vietnam, in August 1964.

It was that supposed incident that misled Congress into “authorizing” military action (the slippery term that now denotes Congress’ abdication of its war-making powers), and duly led to major combat engagement the following year.

The Turner Joy was never attacked, and President Lyndon Johnson was as fully aware of this as George W. Bush was that no reliable evidence existed that Saddam Hussein possessed so-called weapons of mass destruction in Iraq.

It is said that truth is the first casualty of war. In Vietnam and Iraq, lies got the war going in the first place. They just keep coming.

In the present case, the Pentagon has built an interactive Vietnam timeline on its website. It is suitable for adoption by educators, and it glorifies soldierly heroism, downplays the horrific civilian cost of the war (more than two million dead), and the popular resistance that divided America more deeply than at any time since the Civil War.

It also omits the Senate committee hearings on the war at which John Kerry, now Obama’s secretary of state and a decorated veteran, famously asked the lawmakers, “How do you ask a man to be the last man to die for a mistake?”

Of course, Vietnam was no mere mistake. It was a crime under international law, as the unofficial International War Crimes Tribunal established and headed by British philosopher Bertrand Russell pointed out.

It started with the lie that it was necessary to the defense of the homeland, it proceeded with the lie that it was being won, and it ended with the lie that it had been lost not on the battlefield but because of opposition at home — opposition that negated the heroism the Pentagon now wants us to celebrate.

I wish that last lie were the truth. I fought my own Vietnam War in the streets along with millions of other resisters, and I would like to say that we stopped the government from destroying our country. We didn’t, though.

It was a tireless and resourceful enemy that did, and a disillusioned army that drugged itself out and fragged its officers and, in the end, simply made it impossible to prolong the lie of the war further. Now, the veterans who came home from Vietnam — and the 58,000 who didn’t — are being drafted once more to revive the lie all over again.

As a professional historian I am offended by the attempt to make a noble crusade of one of the ugliest chapters in our history; as a participant in the events in question myself, I am personally outraged. (I wish the members of the legal community would take similar umbrage at Obama’s repeated savaging of the Constitution.)

The issue goes beyond historical accuracy.

What the military planners and the civilian warmongers learned from Vietnam was that distant imperial wars become unpopular when the children of the middle class come home in body bags. They fixed this problem by ending the draft; a volunteer army meant death on someone else’s dime, and the underclass from which it was largely recruited had little voice and less influence.

Just in case, the middle class was phased out too by economic contraction, leaving the pursuit of inequality as the American Dream our brave troops would fight and die for.

It worked like a charm. The mass protests of the Vietnam era are now a distant memory as we accommodate ourselves to an endless war that effortlessly morphs from one theater to another. “Vietnam” itself is a word from another century, of little if any meaning to millennials.

Where history has faded, propaganda now moves in, although Kerry (the Benedict Arnold of our time) and his sidekick Chuck Hagel, Defense secretary and also a Vietnam vet, certainly know the truth they defile. Liquidating history isn’t yet as easy as flushing it down Orwell’s memory hole, but when the Pentagon starts offering “curriculum” to the schools the future is assured.

A few aging radicals, to be sure, have risen to make a final protest. But the canonization of Vietnam is a multiyear project, and it will outlast them. Money has been appropriated; more will follow. Traveling exhibits, sanitized oral history projects, and funded symposia (attention, all scholars) are in the works.

It took a while, but in the new virtual reality world we’re being programmed to inhabit, the Vietnam War will finally be won.

Why bother, though, winning a war that’s been all but forgotten? Ah, but Vietnam is the key to the wars of the future. The myth that must be built to serve them is of American righteousness and invincibility — each, of course, the guarantee of the other.

The truth of Vietnam, even as a distant memory, is still the major impediment to that myth. Therefore, that memory must be rewritten to order. After all, if truth is the casualty of war and our wars will never end, well … you know where we go from here.

Before doublethink descends on us for good, though, there’s a memory of my own I’d like to share. Oct. 21, 2017 will be the 50th anniversary of one of the most important events in the history of our country, one that ought to be remembered along with the Fourth of July and Constitution Day. It was the March on the Pentagon, when tens of thousands of citizens breached the sacred precincts of our military temple and went up to a line of armed soldiers with the purpose of ritually levitating the Pentagon off the ground and depositing it, presumably, on some neighboring asteroid.

Some girls in the front line bared their breasts to the soldiers and placed flowers in the barrels of their guns. It was a picnic organized to defeat a war, but a very serious one. When darkness fell and the cameras could no longer record what happened, the state struck back. Heads were bloodied and limp bodies dragged off.

I breathed something that day, something in the air that had never been there before and has not returned since. It was the pungent, intoxicating odor of freedom — not our enumerated civil liberties, not the decorous take-your-turn of orderly debate, but the wild, wonderful essence of the thing itself.

Get a whiff of it sometime, if you can. It smells of truth.

Robert Zaller is a professor of history at Drexel University. He can be contacted at op-ed@thetriangle.org.