WASHINGTON — As Islamic State militants take a pounding in their eroding Iraqi and Syrian strongholds, its leaders have set up a new headquarters in Syria away from the front lines, where they are digging in and likely planning more attacks against the West. The militants' relocation could extend Islamic State's ability to wreak havoc in the region and beyond for months to come.
U.S. officials and Syrian activists say many commanders have fled the besieged cities of Mosul, Iraq, and Raqqa, Syria, in recent months for Mayadeen, a remote town in the heart of Syria's ISIS-controlled, Euphrates River valley near the Iraqi border. Although the U.S.-led coalition is aware of the migration and has launched airstrikes there, its military campaign remains focused on ousting ISIS from its two centers of operation, Mosul and Raqqa.
Militants may already be communicating, coordinating and directing attacks from Mayadeen, about 120 miles (190 kilometers) southeast of Raqqa, at a time when foreign fighters are returning to home countries in Europe, the Middle East, North Africa and Asia and conducting attacks. Command and control of the overall organization is now in the city, said several U.S. officials, who weren't authorized to speak publicly on the matter and demanded anonymity.
"The ground campaign has largely amounted to the U.S. just chasing the (Islamic State) cell around the battlefield," said Jennifer Cafarella, a Syria expert with the Institute for the Study of War. "Every time we get close to it, it moves," she said, noting even reports of Islamic State leader Abu Bakr al-Baghdadi taking haven in the Mayadeen area.
U.S. defense officials dismiss suggestions the coalition hasn't acted forcefully enough to prevent ISIS leaders from moving headquarters and regrouping. But they agree the preponderance of their operations are in Mosul and Raqqa. Iraqi troops are still trying to complete Mosul's takeover, while U.S.-backed Kurdish and Arab forces are only just beginning their operations to seize Raqqa's center.
"If we find them and know where they are, we will strike them," said Col. Ryan Dillon, coalition spokesman in Baghdad.
Islamic State group commanders have been moving their operations and families to Mayadeen for several months as coalition-backed forces began closing in on Raqqa, senior U.S. officials say. They're arriving in an area controlled by Islamic State militants and populated by Sunni sympathizers.
Syrian opposition activists confirm those accounts, saying ISIS brought many of its fighters to Mayadeen. They're now digging trenches around the city, which still draws revenue from nearby oil wells, including the Al-Omar field, among Syria's largest.
Its proximity to the desert and Iraqi border makes ground attacks harder. Sympathetic local tribes have boosted ISIS' authority. And most of ISIS' elite fighters are now in the area, said Ahmad al-Hamade, a Syrian army colonel who defected early in the conflict.
Deir el-Zour province "will be the last battle for Daesh," he said, using an Arabic acronym for ISIS.
It will be the "new capital," said Mohammed Khider, who heads the Sound and Picture Organization that tracks atrocities in ISIS-held areas. "It will be the last castle for the group, and they want it as a capital so the fighters will defend it to death."
ISIS forces converging in Mayadeen face two threats. While the Raqqa fight intensifies in northern Syria, U.S.-backed rebels in the south, near the Jordanian border, had been hoping to march toward the area. Those plans may be complicated by Syrian government troops who have set up outposts around the border town of Tanf, where the U.S.-led coalition trains Syrian rebels.
Syrian government forces could lead a future attack on Mayadeen, having captured significant territory from extremists in recent months and reaching the Iraqi border for the first time in years.
President Bashar Assad's forces, who've been locked in civil war for more than six years with rebel groups, and allied Shiite militiamen are currently marching toward the ISIS stronghold of Sukhna. Regional capital Deir el-Zour would be the next target, with Assad's government looking to break a years-long siege of parts of the city.
A messy fight awaits, whoever ends up leading it.
Tens of thousands of refugees also have descended on Mayadeen, driven from homes in Iraq and Syria by fighting. The exodus puts them in the line of fire at a time the U.S. has been criticized for airstrikes leading to heavy civilian death tolls.
In recent weeks, air attacks on the city have intensified. Residents were preparing for the Muslim holy month of Ramadan in late May when waves of airstrikes struck several neighborhoods, demolishing buildings and killing scores. Many were buried beneath the debris. Casualties overwhelmed hospitals and mosque loudspeakers urged residents to donate blood to the wounded. Activists blamed the U.S.-led coalition, but Russia has also claimed airstrikes there, making it unclear who might be responsible.
The coalition has reported only five airstrikes in or near Mayadeen since late April. The U.S. military, however, said other strikes also have targeted the city but may have been listed in news releases as strikes on nearby, larger and more well-known places such as Deir el-Zour.
Two of the strikes killed Islamic State leaders planning attacks in the West, according to the U.S., including a militant involved with a youth program called "Cubs of the Caliphate," a high-priority training program sanctioned by ISIS' leadership.
Others hit ISIS media and propaganda facilities. Baraa Kadek, founder of ISIS' news agency, was killed with his daughter, his brother claimed.
Innocent civilians have been killed, too, activists say. The Britain-based Syrian Observatory for Human Rights says strikes on Mayadeen have killed 20 IS fighters and 182 others since May 22. The dead include 28 civilians and 154 family members of ISIS fighters, the group said. It tallied 68 children and 57 women killed.
Mroue reported from Beirut.