by JASSEM AL SALAMI

Less than two months after the fall of Mosul to Islamic State, Kurdish leaders worried their own capital would be next.

Fast-moving, well-coordinated Islamic State assaults penetrated Kurdish front lines near Irbil. Fearing the loss of the city, and the opening of a gateway for the jihadists to attack into Iran. Tehran rushed to help.

Tehran waged a battle against Kurdish fighters in northwest Iran less than four years before. Now the mullahs sent weapons, advisers and aerial support for the besieged Peshmerga fighters.

But Iran wants the Kurds to know that aid comes with a price. Especially since the Peshmerga—with an increasing amount of Western aid—are doing better than Iranian-backed Shia militias on the battlefield. It’s enough for Tehran to fear losing influence over its new allies.

As a result, Tehran sent a subtle warning in late December during a meeting in Iraqi Kurdistan between Iranian and Kurdish envoys.

One of the Iranian delegates … was the suspected trigger man who killed one of the most prominent Kurdish leaders in the late 1980s.

Iran knows its support helped save Irbil. Iranian aid was instrumental in resisting Islamic State’s advances, Iraqi Kurdistan Pres. Massoud Barzani told Italian TV station Rai 3 in September.

The Kurds repaid the aid by securing Baquba—a gateway that Islamic State could use to attack Iran. The Peshmerga also helped Shia militias clear Jalawla, the nearest Iraqi town to Iran’s border that fell under Islamic State’s control.

But mutual support is not the whole story. Iran is gravely concerned about Kurdish cooperation with Israel. Mossad had a confirmed presence in Kurdistan during the 1960s and 1970s.

Brig. Gen. Tzuri Sagi was one of the first Israeli commandos to arrive in Kurdistan in 1965 to train Peshmerga fighters. “I saw [Kurdish nationalist leader Mustafa] Barzani every day,” Sagi recalled to Israel-Kurd magazine.

Tehran’s fears of Israeli influence never went away. Israel-Kurd’s editor later went missing—a suspected kidnapping by Iranian agents.

In 2012, Iranian security forces also captured five Kurdish guerrillas accused of assassinating nuclear scientists. Tehran claims four of the five guerrillas worked for Mossad.