Donald J. Trump will go down in history as fully complicit in Turkish war crimes. Unless, that is, he picks up his phone and tells Turkish President Recep Tayyip Erdogan to halt his murderous attack on Syrian Kurds immediately – or face draconian U.S. sanctions.

“War crimes” are the only way to describe what Trump has set in motion with his feckless phone call that green-lit Erdogan’s invasion of Syria. Because make no mistake, what Trump’s buddy is doing has nothing to do with fighting ISIS, and everything to do with destroying the Kurds.

Within the first 24 hours of their invasion, Turkish forces had already driven at least 100,000 Kurdish civilians out of two cities near the Turkish border, many of them fleeing on foot with only the clothes they were wearing. “These cities are almost empty from civilians who have fled to the countryside,” I was told by Syrian Kurdish journalist Rodi Hasan.

The Turks have already moved on to shelling other major Kurdish cities, like the capital, Qamishli.

“He is deliberately bombing the civilian population,” says Steve Gumaer, president of Partners Relief and Development, a small humanitarian relief agency that has staff in northern Syria. Gumaer’s brave team are risking their lives to distribute mattresses and blankets to desperate Kurds fleeing south toward the city of Hasaka. But the Turks have deliberately shelled the water station serving Hasaka, ensuring that the flood of displaced persons won’t have water to survive.

» READ MORE: Another Trump phone call opens door to slaughter of Kurds | Trudy Rubin

So when Trump said earlier this week he expected Erdogan to conduct the offensive “in as humane a way as possible,” his ignorance was sickening.

Erdogan has repeatedly made clear that his goal in northern Syria was to drive out Kurds and replace them with Sunni Arabs. He provided a graphic example in early 2018, when Turkish forces invaded Syria and seized the Kurdish-majority city of Afrin (farther west than the area of the current invasion).

Tens of thousands of civilians fled Afrin, along with Kurdish troops. Ankara replaced them with Syrian Arab refugees living in Turkey, including armed Islamist militias. A U.N. commission of inquiry says these armed groups persecute anyone who objects to Turkish occupation or the Islamists.

Afrin is the template for what Erdogan will do with the rest of Syrian Kurdistan — unless he is stopped.

Yet on Monday a delusional Trump defended his phone call with Erdogan thus: “I spoke with President Erdogan of Turkey, and I said, `Got to treat them [the Kurds] good, and you got to take care of ISIS.' ” Given such delusions about Erdogan — and his own brilliance — no wonder Trump got rolled.

In fact, Erdogan has zero interest in “taking care of ISIS.” The Turkish leader was notorious for letting ISIS fighters cross the Turkish border freely, even letting wounded ISIS fighters use Turkish hospitals. Nor will the Turks assume the role of guarding tens of thousands of ISIS prisoners if Kurdish guards leave to defend Kurdish cities. Expect prison breaks.

Indeed, rather than stop an “endless war,” Trump is on the way to reviving ISIS. But this time the Kurds won’t be there to put the Islamists down.

» READ MORE: Ending "forever wars": Trump will fail by imitating Obama | Trudy Rubin

Assailed by GOP senators, and even conservative Christian leaders, for selling out the Kurds, Trump has called the Turkish invasion “a bad idea”- a weasel-worded effort to whitewash his role.

“I hope we can mediate [between Turks and Kurds],” the president said Thursday.

But mediation is just what U.S. diplomats have been doing for months, trying to get the Turks to accept a narrow, demilitarized buffer strip along the border. With one phone call, Trump ended that U.S. effort. And anyway, it isn’t what Erdogan wants.

The only slim hope of thwarting Erdogan is for Trump to make another call, ASAP. to his Turkish buddy. The message: “Cease fire on and withdraw from Kurdish cities or else I will keep my pledge to ‘wipe out’ your economy with sanctions."

A bipartisan majority in Congress is eager to pass sanctions against Turkey and its leadership, but only a strong Trump stance would convince Ankara the threat was real.

Yet Trump hasn’t rescinded his invitation for Erdogan to visit the White House next month. And U.S. diplomats on Thursday stood with Russia at the United Nations in opposing a resolution condemning Turkey’s invasion. How vile is that!

Aware of congressional wrath, Erdogan is moving fast. There are almost no humanitarian aid groups still working in northern Syria, so a tsunami of Kurds may be compelled to cross into the Kurdish region of Iraq.

That would create a humanitarian disaster of massive proportions. Iraqi Kurdistan, with a population of eight million, cannot handle that burden. (It is already hosting 1.5 million Iraqi and Syrian refugees from ISIS, including many Christians, who can’t go home.)

Trump already has Kurdish blood on his hands, but he has a slim chance to thwart Erdogan’s complete plans.

Here comes the test of whether the GOP senators and televangelists who have slammed Erdogan are or are not total hypocrites: Will they demand that Trump act now to save the Kurds?