WASHINGTON — The Islamic State’s push toward the Kurdish city of Irbil on Thursday came as unwelcome news to those who thought the Kurdish peshmerga militia would be the force most capable of halting the militant Islamists’ momentum.
The United States had such confidence in the Kurds that, in June, it moved its Joint Operation Center and some embassy staff to Irbil, where about 40 U.S. military advisers are now stationed.
Until this week, life in Irbil has been relatively normal despite the Islamic State offensive, which began with the fall of Mosul, Iraq’s second largest city, in early June. Everyone assumed that the Islamic State was shying away from confronting the peshmerga, with its substantial reputation as a fighting force.
But then the Islamic State moved against cities last week that were defended by the peshmerga, and the peshmerga retreated. On Thursday, the Islamic State captured at least four towns on the highway to Irbil and defeated peshmerga forces attempting to break its siege of the Mosul Dam. A near panic took hold in the Kurdish capital as militia forces rushed to set up a defensive line at Kalak, 25 miles northwest of Irbil.
It was another victory for the Islamic State, which before the peshmerga had defeated Syrian forces throughout much of eastern Syria, including recent seizures of major Syrian bases in Raqqa and Deir el Zour, and had sent Iraqi army forces fleeing almost to the gates of Baghdad.
What has made the Islamic State forces seemingly unstoppable?
Observers on the ground and analysts in Washington think the latest push was possible because the peshmerga forces are stretched trying to defend a frontier with the Islamic State that is almost 900 miles long. The Islamic State is also better equipped, with U.S.-supplied weapons that its forces have looted from every Iraqi military based it has seized. It also has recently captured major Syrian arsenals.
On Twitter, the Islamic State often posts photos of its bounty from military bases, which include rocket-propelled-grenade launchers, artillery and weapons that are far more sophisticated than those in the peshmerga arsenal.
The Islamic State also has the advantage of momentum. According to the Long Wars Journal, citing a tweet by the Islamic State, its forces have taken control of 17 communities in the area around Mosul. Its push stretches all the way to Diyala province in northeast Iraq, which borders Iran. On Thursday, the Islamic State claimed to control the Mosul Dam, the largest water supply source in Iraq — a claim U.S. and Iraqi sources confirmed.
And perhaps most importantly, the Islamic State has very simply put together a smarter offensive plan. Its push toward Irbil is thought by many not to be a move to take that city but to force the peshmerga to defend its capital, allowing the Islamic State to harden its grip on places nearby it’s more interested in holding.
“No one is doing what ISIS is doing,” said Jessica Lewis, a research director at the Washington-based Institute for the Study of War, using one acronym for the Islamic State derived from its previous name, the Islamic State of Iraq and Syria. “ISIS thins out and strategically targets their adversaries. They are more thoughtful about their offense.”
In Sunni-dominated Iraqi cities such as Mosul and Fallujah, the Islamic State successfully co-opted or intimidated residents, allowing its forces to move in and take over. In Kurdish-defended areas, it has forced the peshmerga to defend multiple locations along the lengthy frontier.
The Kurds have made no secret of their limitations. They have repeatedly asked the United States for help.
Many analysts think the Islamic State’s current push in northern Iraq, seizing cities such as Sinjar and Bartella that lie east of Mosul, is intended to create a buffer between the Kurdish region and the self-declared Islamic caliphate. For the Islamic State, cities such as Sinjar potentially form the outer border of a contiguous state.
“They are trying to carve out the territorial integrity of their Islamic State,” Lewis said.
Against this backdrop, Kurdish Regional Government President Masoud Barzani reportedly issued a statement this week, condemning the Islamic State for attacking Christians, thousands of whom fled to the Kurdish region.
Lewis said there was another reason to doubt that the Islamic State wants to seize Irbil. Unlike Mosul, where the Islamic State had operated for years and had built a support network, Irbil is a Kurdish city of 1.5 million people committed to keeping the Islamic State out. Moreover, Irbil does not border the proposed Islamic caliphate.
Rather, Lewis thinks the Islamic State wants to lock peshmerga forces into defending the capital, which would leave other places that it seeks to control vulnerable. It allows the Islamic State to decide the terms of battle — something it has been able to do since early June.
“ISIS is maintaining the initiative,” she said.