The killing of Islamic State co-founder, operations overseer, and key spokesman Abu Muhammad al-Adnani is good news for the U.S. military and its coalition of forces fighting the terrorist group inside Syria. But it comes after a week that has shown just how hard it is for the U.S. to keep members of the counter-ISIS coalition aligned and focused on the fight against ISIS rather than one another.

Turkey, America’s NATO ally and Incirlik Air Base host, is critical to the U.S. fight against ISIS. So are the Kurdish forces, the YPG and YPJ, who have been leading the frontline fight that is squeezing the ISIS “caliphate” to its core. But in the last week those two allies against ISIS (but adversaries to one another) have collided. Suddenly, the fight against ISIS, right at the moment when it is gaining momentum, is stuck in the crossfire between Turks and Kurds, leaving American officials to de-conflict the situation among their own coalition partners.

America’s war planners once again find themselves in a situation that shows how tricky just-in-time policymaking can be when relying on local forces who have their own interests to pursue, not just Washington’s.

In some ways this is the natural extension of what has come to be known as the Obama Doctrine – in which the U.S. would seek local forces to fight their own wars, send limited numbers of American troops, but not commit large numbers of U.S. forces. Right now U.S. troops, particularly special operations forces, are on the ground as advisers leading an advise and-assist mission against ISIS, but they are not leading the way into battle.

This policy means that most of the several thousand American forces operating inside Iraq and Syria do not face the same risks and dangers U.S. troops faced when there were more than 160,000 in Iraq and 100,000 in Afghanistan fighting and dying by the thousands. It also means that, as one person close to the fight told Defense One, American forces are operating from a distance and without the same level of precise control of either operation or outcome. This makes the messy fight on the ground between the Turks and the Kurds — both U.S. allies in the American-led fight against ISIS — easy to anticipate but harder to resolve once it occurs.

Others close to the ISIS fight say that when it comes to U.S. policy, information flow inside the administration has been tricky at best and nonexistent at worst, a fact that is complicated by the complex dynamics on the ground among allies who are sometimes at odds.

“This is not going to turn out well; it starts with the basics of using locals as our infantry,” says former U.S. Ambassador to Iraq James Jeffrey, who has been critical of the Obama administration for limiting U.S. military intervention against ISIS to rely so heavily on local fighters. “Letting them do it isn't working out too well, is it, when they start fighting each other?”

Indeed, it is hard to understand why policy is being made seemingly on the fly when the conflict between Turkey and the Kurds was so easy to foresee. And when both partners matter — but one clearly matters more.

“We have made it absolutely clear to the elements that were part of the Syrian Democratic Forces, the YPG that participated, that they must move back across the river,” Vice President Joe Biden said last week in Ankara. “They cannot, will not, and under no circumstances get American support if they do not keep that commitment, period.”

For his part, the Turkish Prime stood shoulder-to-shoulder with Biden and called America’s allies part of the problems.

“The U.S. should know that at the end of the day, you might maybe use a terrorist organization to defeat another one, but what you have in hand at the end of the day is that terrorist organization that you used, or that you benefitted from, and how do you deal with that terrorist organization?” said Prime Minister Binali Yildrim. “In order not to have a greater threat, I think that would be the right approach with regard to PYD and YPG.”

A few days later, on Monday, Defense Secretary Ash Carter called for both sides to play nicely as he tried to negotiate calm among the key American allies.

“We've called on both sides to not fight with one another, to continue to focus the fight on ISIL. That's the basis of our cooperation with both of them. And specifically, not to engage one another and to retain those geographic commitments that they've made,” he said at the Pentagon. “We do understand that they have historical differences with one another, but American interests are quite clear. We are -- we, like they, want to combat ISIL and we want -- we're calling on them all now. Let's keep our priorities clear here in helping them to deconflict, so to speak, on the battlefield.”

On Tuesday, Gen. Joseph Votel, commander of U.S. Central Command which overseas the war and former commander of U.S. Special Operations Command, which fields America’s elite troops in the fight, spoke of the challenge he faces after getting a battery of questions from Pentagon reporters who wanted to know how he dealt with American allies threatening one another.

“Generally speaking, I do believe our approach, which requires that we work by, with, and through the indigenous forces, is working,” Votel said, before acknowledging the intra-coalition fight. “What we are trying to do is ensure that we keep all of our partners focused on ISIL at this point. It's not helpful to — in-fighting among themselves, we don't want that. We're working to prevent that.”

Add one more task to the fight against ISIS.