Defense Secretary Jim Mattis in Washington on June 21. (Andrew Harrer/Bloomberg News)

Imagine that the president’s national security team walked into the Oval Office and proposed the following U.S. policy in Syria: Let’s create an al-Qaeda haven in southern Syria, by working with Russia to establish a cease-fire area where the terrorist network behind 9/11 is free to operate without fear of U.S. attack.

Then let’s have the Pentagon tell most pro-American Sunnis who want to fight with us that we will arm and train them only if they sign a pledge promising not to fight the regime of Bashar al-Assad, which has massacred their families with mortars and poison gas — likely driving most of the fighters into the waiting arms of al-Qaeda (which promises to help them against Assad). Then let’s cancel the covert CIA program under which we did allow a small number of rebels to fight Assad, and put out word that we are doing so as a concession to Moscow.

Instead of Sunni fighters, we’ll team up with the Kurdish Marxist “People’s Defense Force” (YPG), a terrorist organization at odds with NATO ally Turkey. We’ll use the YPG to attack just the Islamic State, leaving al-Qaeda unscathed and thus helping it reassert its supremacy over its rival for leadership of the global jihad.

Let’s also have Defense Secretary Jim Mattis say publicly that we shouldn’t do anything to push back on the unprecedented expansion of Iranian military force in Syria, and even suggest that Iran can help with the fight against the Islamic State — totally undercutting the president’s stated aim of being tough on Iran. Then we’ll have Secretary of State Rex Tillerson state that “Russia has the same . . . interest that we do” in Syria so we can help al-Qaeda recruit more Sunnis to its cause by telling them that the United States is allied with Russia, Iran, Shiites, Alawites and Kurds in a campaign to annihilate them — a message against which we will have no effective response because it will be true.

Sound like a good plan? Because that is a description of precisely what the Trump administration is doing in Syria today.

“Current US strategy empowers al-Qaeda, which has an army in Syria, is preparing to replace ISIS . . . [and] is more dangerous than ISIS,” says a recent report from the Institute for the Study of War (ISW) and the American Enterprise Institute’s Critical Threats Project (CTP). Our approach, the report declares, “is inadvertently fueling the global Salafi-jihadi insurgency” because Sunnis see the United States as working with their mortal enemies. Al-Qaeda is taking advantage of this perception to build support among Sunni tribes, portraying itself as the defender of Sunni Arabs against a U.S.-Russo-Iranian axis intent on subjugating and destroying them.

Alienating the Sunni population is not the way to win the war against Islamist radicalism. Right now, al-Qaeda has established itself as the tip of the spear in the fight against the Assad regime, so many Sunnis who do not share al-Qaeda’s ideology are flocking to al-Qaeda because it is the only game in town for fighting Assad. Al-Qaeda’s goal is to take charge of the anti-Assad uprising and slowly transform it into a global jihad against Iran, Russia and the United States. Instead of undermining these efforts, we are helping them, by focusing almost exclusively on the Islamic State and driving the Sunni population to ally itself with al-Qaeda.

This is insane. We should be working to strip Sunni tribes away from al-Qaeda. And the United States has a proven record to draw on. During the 2007 surge in Iraq, we successfully rallied the Sunni tribes that had been fighting alongside al-Qaeda in Iraq and got them to turn on the terrorists and help us drive them out. The result was both a military and ideological defeat for the Salafi-jihadist cause. Not only were the terrorists driven from their havens, but also they suffered a humiliating popular rejection by the very Sunni masses of whom they claimed to be the vanguard.

We need a similar military and ideological victory in Syria. So why are we not working to repeat this success? We need to restore the CIA’s covert train-and-equip program and lift the Defense Department’s restrictions preventing Sunnis who join us from fighting the Assad regime. We must then facilitate the emergence of a Sunni Arab partner force in southern Syria that will fight alongside U.S. forces to expel not just the Islamic State but al-Qaeda as well, while helping stop Iran from imposing Persian-backed domination by the Alawite minority against the Sunni majority. As the ISW-CTP report puts it, “We must stop attacking the Sunni Arab community from the outside through proxies, and instead embed ourselves within that population as its defenders.”

The Trump administration needs to understand a fundamental truth: We cannot defeat the Islamic State or al-Qaeda or the global jihadist movement on our own. We cannot do it with Kurdish or Iranian proxies.

We need Sunnis to do it.

Read more from Marc Thiessen’s archive, follow him on Twitter or subscribe to his updates on Facebook.