This pattern of “seduction and abandonment” is one of our least endearing characteristics. It’s one reason the United States is mistrusted in the Middle East. We don’t stick by the people who take risks on our behalf in Iraq, Egypt, Lebanon and elsewhere. And now, I fear, this syndrome is happening again in Syria, as a Kurdish militia group known as the YPG, which has been the United States’ best ally against the Islamic State, gets pounded by the Turkish military.

The YPG is a special case for me because I had a chance to meet some of their fighters in May at a secret U.S. Special Operations forces training camp in northern Syria. They described battling to the last man — and sometimes woman — as they drove the Islamic State from its strongholds. Special Ops officers embedded with the YPG recounted their battlefield exploits with deep respect, expressing what one called “the brotherhood of the close fight.”

Unfortunately, allying with the United States can be a dangerous proposition in the Middle East. Last Thursday, Turkey said its warplanes shot 18 targets in YPG-controlled areas of northern Syria. The Turks want to block the YPG from linking up with its fighters in a pocket known as Afrin, northwest of Aleppo. The Turks also want to prevent the YPG from playing a leading role in the liberation of Raqqa, the Islamic State’s capital, as the United States had planned.

“If it doesn’t stop, it could preempt all plans for Raqqa,” warns a Pentagon official about the Turkish onslaught. Kurdish sources tell me that because the United States isn’t responding to pleas about Afrin, the YPG is appealing to Russia.