This is precisely the sort of debacle that President Barack Obama appeared to be aiming to stop when he announced, last month, that the U.S. military would begin carrying out air strikes against ISIS targets in Syria. (It had been bombing ISIS in Iraq since early August.) American jets have begun hitting the group’s trucks and compounds in Syria, including targets near Kobani, but these attacks have not stopped the ISIS advance. Why is the situation turning out so badly?

The answers are pretty simple, and they aren’t exactly heartening. The first concerns our main ally in the region, Turkey, a NATO member and a democracy whose President, Recep Tayyip Erdoğan, promised to help the United States in destroying ISIS. The White House would like Turkey, which shares a five-hundred-mile border with Syria, to help rescue the people of Kobani, an effort that could possibly include sending troops or directing military support across the border. At the same time, the Kurds inside Syria simply want the Turkish government to allow reinforcements to pass through Turkey from other parts of Syria on their way to Kobani. So far, Erdoğan has been happy to let the people of Kobani face ISIS alone. Turkish soldiers are watching the encirclement of Kobani from their positions a few hundred yards away.

We shouldn’t be shocked. The truth is that, when it comes to ISIS, Erdoğan has other priorities. Ever since ISIS‘s emergence in Syria, in late 2012, Erdoğan, an avowed Islamist politician, has maintained a less than hostile relationship with the group. Indeed, since 2011, when the Syrian civil war broke out, Turkish officials have allowed hundreds, if not thousands, of militants to travel through Turkey and cross into Syria to fight the government of Bashar al-Assad. Border agents haven’t exactly quizzed the fighters about which groups they intend to join when they get there. The Turkish government has provided money and support for all manner of Syrian opposition fighters, often so indiscriminately that money has ended up in the hands of groups like ISIS and Jabhat al-Nusra, the local Al Qaeda franchise. When Vice-President Joe Biden publicly complained about this last week, Erdoğan threw one of his typical—and, in this case, utterly disingenuous—temper tantrums, demanding an apology. Biden hadn’t misspoken; the problem for Erdoğan was that he had spoken the truth. (It’s a tendency that, as Evan Osnos has written, has gotten Biden in trouble before.) Biden should have stuck to his guns; unfortunately, he apologized. There have been persistent reports of wounded ISIS fighters receiving treatment in Turkish hospitals close to the border with Syria. What it comes down to is that ISIS has been pursuing a policy that Turkey strongly favors—the overthrow of Assad—and Turkey, for that reason, has been reluctant to join in the fight against the extremist group.