The Islamic State is losing ground — that’s the good news. The bad news is that our Kurdish allies are now facing a civil war with our Iraqi allies.

It’s hugely encouraging that the Islamic State has been beaten back by a joint effort of U.S.-backed Iraqi and Kurdish forces. The road hasn’t been easy. In 2014, when the Iraqi army’s divisions collapsed and abandoned the northern region to the Islamic State, the Kurds’ Peshmerga saved the day, driving back the Islamic State, including saving Kirkuk. Gradually, that battle continued and the Islamic State is now a shell of its former self. Indeed, the Kurds also this week achieved victory over the Islamic State in its de facto capital of Raqqa, Syria.

But with the Islamic State threat being reduced, and once the Kurds voted to break away from Iraq last month — a referendum opposed by the U.S. — the Iraqi government turned on them with its increasingly capable military, taking back Kirkuk in the process.

So far, Shiite militias are playing only a supporting role to the Iraqi army, but that may change. Ed Morrissey writes, “The Iranian-backed Shi'ite militias appear to be driving this outcome, forcing [Iraqi Prime Minister] Haider al-Abadi to act with force against the Kurds — and thereby confirming the Kurds’ worst fears about the Iraq federation’s future direction. If Iraq falls completely under Iran’s thumb, it will spell the end of the autonomy that Kurds have enjoyed since the end of the 1991 Gulf War.” Indeed, Iraq post-American withdrawal has come ever more under the influence of Iran, which just happens to be ticked off at Trump’s decertification of the nuclear deal.

On that note, David French, a veteran of the U.S. fight in Iraq, highlights the real lesson here: Barack Obama’s disastrous withdrawal from Iraq. “Perhaps the best way to plot a course ahead is to remember the road behind,” French argues. “Back in 2008, we won a military victory in Iraq. In the aftermath of that victory, we withdrew our troops from the country, leaving Iraq to its own devices. The result was catastrophic.”

So, he says, “‘Win and leave’ won’t work. There is too much volatility, and the costs of instability are too high. There’s no guarantee that ‘win and stay’ will yield the results we want, but by staying we’ll retain our power and influence. We know all too well the cost of withdrawal. It’s time we discovered the benefits of long-term, strategic engagement.”

The Trump administration must back the Kurds and pressure the Iraqi government to work out a deal. Abandoning our Kurdish allies would send all the wrong signals in a volatile region.