Two days after the US drone strike in Iraq that killed Iranian Gen. Qassem Soleimani, the Iraqi parliament passed a measure directing the government to oust American troops from its soil. The following day, a senior Marine Corps commander sent a letter notifying Iraqi officials that US forces “respect your sovereign decision to order our departure,” and would begin preparations for “movement out of Iraq.”

So US troops are finally heading home?

Of course not.

The parliamentary resolution adopted on Sunday, though heavily played up by American media, was merely a nonbinding request and had the support of only Shiite lawmakers — most of the Sunni and Kurdish members boycotted the session. According to the Wall Street Journal, Kataib Hezbollah, a Shiite terrorist group backed by Iran, threatened vengeance against any member of parliament voting No on the resolution.

And just as Iraq’s government isn’t actually expelling US troops, US troops aren’t actually planning to leave. The letter from Marine Gen. William Seely turned out to be an unsigned draft released by mistake. “There’s been no decision made to leave Iraq,” said Defense Secretary Mark Esper. “Period.”

The whole episode embodied, in miniature, the single most obstinate reality of America’s involvement in Iraq and the Middle East. Withdrawing our troops may seem a straightforward objective, but it just isn’t possible.

Pledges to get America out of the Muslim world have become as much a part of presidential campaigns as rallies and fundraising letters. Bernie Sanders, denouncing “endless war,” vows to pull the plug on US “military interventions” in Iraq and Afghanistan. Pete Buttigieg promises that if he becomes president there will be no “open-ended” commitment of troops in the region, and intones: “The best way not to be caught up in endless war is to avoid starting one in the first place.” Elizabeth Warren declares flatly: “We ought to get out of the Middle East. I don’t think we should have troops in the Middle East.”

Yet the Democrats are saying nothing that Donald Trump didn’t say when he was running to succeed Barack Obama.

“We should have never been in Iraq,” Trump insisted during one 2016 debate. “We’ve been in the Middle East for 15 years, and we haven’t won anything.” He called for a total US withdrawal from Afghanistan. One of Trump’s “most consistent and specific positions,” Reason magazine recalled last year, was his “skepticism about American military interventions in other countries.”

Then again, the same was true of Obama when he ran for the White House. “I’ll be a president who ends this war in Iraq and finally brings our troops home,” he assured voters in 2008. Eight years before that, George W. Bush made clear that American foreign policy had to be “humble” and that “we can’t put our troops all around the world.”

In fact, US troops are deployed in most of the world’s countries; in some cases they’ve been present for more than 70 years. Most of those deployments aren’t controversial because they aren’t hazardous or in regions roiled by dictators or terrorism. The American presence in the Middle East is so vexing precisely because that part of the world is constantly in crisis and has so many hostile actors.

Which is why America can’t leave, as presidents to their chagrin keep learning the hard way.

Obama came to office convinced that America needed to lower its profile in the Middle East. He favored a foreign policy in which Washington eschewed intervention and practiced restraint. Sticking to that policy, he pulled US troops from Iraq, refused to assist protesters in Iran, and didn’t retaliate when Syria deployed chemical weapons. The results were disastrous. “After the United States left Iraq in 2011,” writes historian Hal Brands, “the state nearly collapsed, ISIS surged to prominence, and an emergency military intervention — which has now lasted nearly five years — was needed to repair the damage.”

Until Thursday, Trump was largely following in Obama’s footsteps. Iranian attacks — from firing missiles at Persian Gulf oil tankers to shooting down a US drone — were growing increasingly brazen. When a US contractor was killed in Kirkuk, Trump finally decided that a red line had been crossed, and meted a lethal punishment to Iran’s terror master.

Does the killing of Soleimani presage a fundamental change in strategy? Will rolling back Iran’s widening aggression become a serious US priority at last? That, no one yet knows. All we can know for sure is that America won’t be leaving the region anytime soon.

Like it or not, the United States cannot abandon the Middle East without quickening its enemies and unleashing fresh chaos. Whoever wins the White House in 2020, the world’s most treacherous and dangerous neighborhood will need the stabilizing presence of the world’s democratic superpower. US troops have been permanently deployed in the Middle East for 30 years. It will likely be another 30 before they can safely leave.

(Jeff Jacoby is a columnist for The Boston Globe).